auto merge of #10965 : alexcrichton/rust/libgreen, r=brson

This pull request extracts all scheduling functionality from libstd, moving it into its own separate crates. The new libnative and libgreen will be the new way in which 1:1 and M:N scheduling is implemented. The standard library still requires an interface to the runtime, however, (think of things like `std::comm` and `io::println`). The interface is now defined by the `Runtime` trait inside of `std::rt`.

The booting process is now that libgreen defines the start lang-item and that's it. I want to extend this soon to have libnative also have a "start lang item" but also allow libgreen and libnative to be linked together in the same process. For now though, only libgreen can be used to start a program (unless you define the start lang item yourself). Again though, I want to change this soon, I just figured that this pull request is large enough as-is.

This certainly wasn't a smooth transition, certain functionality has no equivalent in this new separation, and some functionality is now better enabled through this new system. I did my best to separate all of the commits by topic and keep things fairly bite-sized, although are indeed larger than others.

As a note, this is currently rebased on top of my `std::comm` rewrite (or at least an old copy of it), but none of those commits need reviewing (that will all happen in another pull request).

24 files changed, 625 insertions, 5715 deletions

diff --git a/src/libstd/rt/basic.rs b/src/libstd/rt/basic.rs
deleted file mode 100644
index 3589582357c..00000000000
--- a/src/libstd/rt/basic.rs
+++ /dev/null
@@ -1,230 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! This is a basic event loop implementation not meant for any "real purposes"
-//! other than testing the scheduler and proving that it's possible to have a
-//! pluggable event loop.
-
-use prelude::*;
-
-use cast;
-use rt::rtio::{EventLoop, IoFactory, RemoteCallback, PausableIdleCallback,
-               Callback};
-use unstable::sync::Exclusive;
-use io::native;
-use util;
-
-/// This is the only exported function from this module.
-pub fn event_loop() -> ~EventLoop {
-    ~BasicLoop::new() as ~EventLoop
-}
-
-struct BasicLoop {
-    work: ~[proc()],                  // pending work
-    idle: Option<*mut BasicPausable>, // only one is allowed
-    remotes: ~[(uint, ~Callback)],
-    next_remote: uint,
-    messages: Exclusive<~[Message]>,
-    io: ~IoFactory,
-}
-
-enum Message { RunRemote(uint), RemoveRemote(uint) }
-
-impl BasicLoop {
-    fn new() -> BasicLoop {
-        BasicLoop {
-            work: ~[],
-            idle: None,
-            next_remote: 0,
-            remotes: ~[],
-            messages: Exclusive::new(~[]),
-            io: ~native::IoFactory as ~IoFactory,
-        }
-    }
-
-    /// Process everything in the work queue (continually)
-    fn work(&mut self) {
-        while self.work.len() > 0 {
-            for work in util::replace(&mut self.work, ~[]).move_iter() {
-                work();
-            }
-        }
-    }
-
-    fn remote_work(&mut self) {
-        let messages = unsafe {
-            self.messages.with(|messages| {
-                if messages.len() > 0 {
-                    Some(util::replace(messages, ~[]))
-                } else {
-                    None
-                }
-            })
-        };
-        let messages = match messages {
-            Some(m) => m, None => return
-        };
-        for message in messages.iter() {
-            self.message(*message);
-        }
-    }
-
-    fn message(&mut self, message: Message) {
-        match message {
-            RunRemote(i) => {
-                match self.remotes.mut_iter().find(|& &(id, _)| id == i) {
-                    Some(&(_, ref mut f)) => f.call(),
-                    None => unreachable!()
-                }
-            }
-            RemoveRemote(i) => {
-                match self.remotes.iter().position(|&(id, _)| id == i) {
-                    Some(i) => { self.remotes.remove(i); }
-                    None => unreachable!()
-                }
-            }
-        }
-    }
-
-    /// Run the idle callback if one is registered
-    fn idle(&mut self) {
-        unsafe {
-            match self.idle {
-                Some(idle) => {
-                    if (*idle).active {
-                        (*idle).work.call();
-                    }
-                }
-                None => {}
-            }
-        }
-    }
-
-    fn has_idle(&self) -> bool {
-        unsafe { self.idle.is_some() && (**self.idle.get_ref()).active }
-    }
-}
-
-impl EventLoop for BasicLoop {
-    fn run(&mut self) {
-        // Not exactly efficient, but it gets the job done.
-        while self.remotes.len() > 0 || self.work.len() > 0 || self.has_idle() {
-
-            self.work();
-            self.remote_work();
-
-            if self.has_idle() {
-                self.idle();
-                continue
-            }
-
-            unsafe {
-                // We block here if we have no messages to process and we may
-                // receive a message at a later date
-                self.messages.hold_and_wait(|messages| {
-                    self.remotes.len() > 0 &&
-                        messages.len() == 0 &&
-                        self.work.len() == 0
-                })
-            }
-        }
-    }
-
-    fn callback(&mut self, f: proc()) {
-        self.work.push(f);
-    }
-
-    // XXX: Seems like a really weird requirement to have an event loop provide.
-    fn pausable_idle_callback(&mut self, cb: ~Callback) -> ~PausableIdleCallback {
-        let callback = ~BasicPausable::new(self, cb);
-        rtassert!(self.idle.is_none());
-        unsafe {
-            let cb_ptr: &*mut BasicPausable = cast::transmute(&callback);
-            self.idle = Some(*cb_ptr);
-        }
-        return callback as ~PausableIdleCallback;
-    }
-
-    fn remote_callback(&mut self, f: ~Callback) -> ~RemoteCallback {
-        let id = self.next_remote;
-        self.next_remote += 1;
-        self.remotes.push((id, f));
-        ~BasicRemote::new(self.messages.clone(), id) as ~RemoteCallback
-    }
-
-    fn io<'a>(&'a mut self) -> Option<&'a mut IoFactory> {
-        let factory: &mut IoFactory = self.io;
-        Some(factory)
-    }
-}
-
-struct BasicRemote {
-    queue: Exclusive<~[Message]>,
-    id: uint,
-}
-
-impl BasicRemote {
-    fn new(queue: Exclusive<~[Message]>, id: uint) -> BasicRemote {
-        BasicRemote { queue: queue, id: id }
-    }
-}
-
-impl RemoteCallback for BasicRemote {
-    fn fire(&mut self) {
-        unsafe {
-            self.queue.hold_and_signal(|queue| {
-                queue.push(RunRemote(self.id));
-            })
-        }
-    }
-}
-
-impl Drop for BasicRemote {
-    fn drop(&mut self) {
-        unsafe {
-            self.queue.hold_and_signal(|queue| {
-                queue.push(RemoveRemote(self.id));
-            })
-        }
-    }
-}
-
-struct BasicPausable {
-    eloop: *mut BasicLoop,
-    work: ~Callback,
-    active: bool,
-}
-
-impl BasicPausable {
-    fn new(eloop: &mut BasicLoop, cb: ~Callback) -> BasicPausable {
-        BasicPausable {
-            active: false,
-            work: cb,
-            eloop: eloop,
-        }
-    }
-}
-
-impl PausableIdleCallback for BasicPausable {
-    fn pause(&mut self) {
-        self.active = false;
-    }
-    fn resume(&mut self) {
-        self.active = true;
-    }
-}
-
-impl Drop for BasicPausable {
-    fn drop(&mut self) {
-        unsafe {
-            (*self.eloop).idle = None;
-        }
-    }
-}
diff --git a/src/libstd/rt/borrowck.rs b/src/libstd/rt/borrowck.rs
index 423981d9e91..d1e97cb6ec0 100644
--- a/src/libstd/rt/borrowck.rs
+++ b/src/libstd/rt/borrowck.rs
@@ -12,9 +12,8 @@ use c_str::{ToCStr, CString};
 use libc::{c_char, size_t};
 use option::{Option, None, Some};
 use ptr::RawPtr;
-use rt::env;
+use rt;
 use rt::local::Local;
-use rt::task;
 use rt::task::Task;
 use str::OwnedStr;
 use str;
@@ -62,7 +61,7 @@ unsafe fn fail_borrowed(alloc: *mut raw::Box<()>, file: *c_char, line: size_t)
     match try_take_task_borrow_list() {
         None => { // not recording borrows
             let msg = "borrowed";
-            msg.with_c_str(|msg_p| task::begin_unwind_raw(msg_p, file, line))
+            msg.with_c_str(|msg_p| rt::begin_unwind_raw(msg_p, file, line))
         }
         Some(borrow_list) => { // recording borrows
             let mut msg = ~"borrowed";
@@ -76,7 +75,7 @@ unsafe fn fail_borrowed(alloc: *mut raw::Box<()>, file: *c_char, line: size_t)
                     sep = " and at ";
                 }
             }
-            msg.with_c_str(|msg_p| task::begin_unwind_raw(msg_p, file, line))
+            msg.with_c_str(|msg_p| rt::begin_unwind_raw(msg_p, file, line))
         }
     }
 }
@@ -95,7 +94,7 @@ unsafe fn debug_borrow<T,P:RawPtr<T>>(tag: &'static str,
     //! A useful debugging function that prints a pointer + tag + newline
     //! without allocating memory.
 
-    if ENABLE_DEBUG && env::debug_borrow() {
+    if ENABLE_DEBUG && rt::env::debug_borrow() {
         debug_borrow_slow(tag, p, old_bits, new_bits, filename, line);
     }
 
@@ -180,7 +179,7 @@ pub unsafe fn unrecord_borrow(a: *u8,
             if br.alloc != a || br.file != file || br.line != line {
                 let err = format!("wrong borrow found, br={:?}", br);
                 err.with_c_str(|msg_p| {
-                    task::begin_unwind_raw(msg_p, file, line)
+                    rt::begin_unwind_raw(msg_p, file, line)
                 })
             }
             borrow_list
diff --git a/src/libstd/rt/context.rs b/src/libstd/rt/context.rs
deleted file mode 100644
index 31cf0696881..00000000000
--- a/src/libstd/rt/context.rs
+++ /dev/null
@@ -1,463 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-use option::*;
-use super::stack::StackSegment;
-use libc::c_void;
-use uint;
-use cast::{transmute, transmute_mut_unsafe,
-           transmute_region, transmute_mut_region};
-
-pub static RED_ZONE: uint = 20 * 1024;
-
-// FIXME #7761: Registers is boxed so that it is 16-byte aligned, for storing
-// SSE regs.  It would be marginally better not to do this. In C++ we
-// use an attribute on a struct.
-// FIXME #7761: It would be nice to define regs as `~Option<Registers>` since
-// the registers are sometimes empty, but the discriminant would
-// then misalign the regs again.
-pub struct Context {
-    /// The context entry point, saved here for later destruction
-    priv start: Option<~proc()>,
-    /// Hold the registers while the task or scheduler is suspended
-    priv regs: ~Registers,
-    /// Lower bound and upper bound for the stack
-    priv stack_bounds: Option<(uint, uint)>,
-}
-
-impl Context {
-    pub fn empty() -> Context {
-        Context {
-            start: None,
-            regs: new_regs(),
-            stack_bounds: None,
-        }
-    }
-
-    /// Create a new context that will resume execution by running proc()
-    pub fn new(start: proc(), stack: &mut StackSegment) -> Context {
-        // FIXME #7767: Putting main into a ~ so it's a thin pointer and can
-        // be passed to the spawn function.  Another unfortunate
-        // allocation
-        let start = ~start;
-
-        // The C-ABI function that is the task entry point
-        extern fn task_start_wrapper(f: &proc()) {
-            // XXX(pcwalton): This may be sketchy.
-            unsafe {
-                let f: &|| = transmute(f);
-                (*f)()
-            }
-        }
-
-        let fp: *c_void = task_start_wrapper as *c_void;
-        let argp: *c_void = unsafe { transmute::<&proc(), *c_void>(&*start) };
-        let sp: *uint = stack.end();
-        let sp: *mut uint = unsafe { transmute_mut_unsafe(sp) };
-        // Save and then immediately load the current context,
-        // which we will then modify to call the given function when restored
-        let mut regs = new_regs();
-        unsafe {
-            rust_swap_registers(transmute_mut_region(&mut *regs), transmute_region(&*regs));
-        };
-
-        initialize_call_frame(&mut *regs, fp, argp, sp);
-
-        // Scheduler tasks don't have a stack in the "we allocated it" sense,
-        // but rather they run on pthreads stacks. We have complete control over
-        // them in terms of the code running on them (and hopefully they don't
-        // overflow). Additionally, their coroutine stacks are listed as being
-        // zero-length, so that's how we detect what's what here.
-        let stack_base: *uint = stack.start();
-        let bounds = if sp as uint == stack_base as uint {
-            None
-        } else {
-            Some((stack_base as uint, sp as uint))
-        };
-        return Context {
-            start: Some(start),
-            regs: regs,
-            stack_bounds: bounds,
-        }
-    }
-
-    /* Switch contexts
-
-    Suspend the current execution context and resume another by
-    saving the registers values of the executing thread to a Context
-    then loading the registers from a previously saved Context.
-    */
-    pub fn swap(out_context: &mut Context, in_context: &Context) {
-        rtdebug!("swapping contexts");
-        let out_regs: &mut Registers = match out_context {
-            &Context { regs: ~ref mut r, .. } => r
-        };
-        let in_regs: &Registers = match in_context {
-            &Context { regs: ~ref r, .. } => r
-        };
-
-        rtdebug!("noting the stack limit and doing raw swap");
-
-        unsafe {
-            // Right before we switch to the new context, set the new context's
-            // stack limit in the OS-specified TLS slot. This also  means that
-            // we cannot call any more rust functions after record_stack_bounds
-            // returns because they would all likely fail due to the limit being
-            // invalid for the current task. Lucky for us `rust_swap_registers`
-            // is a C function so we don't have to worry about that!
-            match in_context.stack_bounds {
-                Some((lo, hi)) => record_stack_bounds(lo, hi),
-                // If we're going back to one of the original contexts or
-                // something that's possibly not a "normal task", then reset
-                // the stack limit to 0 to make morestack never fail
-                None => record_stack_bounds(0, uint::max_value),
-            }
-            rust_swap_registers(out_regs, in_regs)
-        }
-    }
-}
-
-extern {
-    fn rust_swap_registers(out_regs: *mut Registers, in_regs: *Registers);
-}
-
-// Register contexts used in various architectures
-//
-// These structures all represent a context of one task throughout its
-// execution. Each struct is a representation of the architecture's register
-// set. When swapping between tasks, these register sets are used to save off
-// the current registers into one struct, and load them all from another.
-//
-// Note that this is only used for context switching, which means that some of
-// the registers may go unused. For example, for architectures with
-// callee/caller saved registers, the context will only reflect the callee-saved
-// registers. This is because the caller saved registers are already stored
-// elsewhere on the stack (if it was necessary anyway).
-//
-// Additionally, there may be fields on various architectures which are unused
-// entirely because they only reflect what is theoretically possible for a
-// "complete register set" to show, but user-space cannot alter these registers.
-// An example of this would be the segment selectors for x86.
-//
-// These structures/functions are roughly in-sync with the source files inside
-// of src/rt/arch/$arch. The only currently used function from those folders is
-// the `rust_swap_registers` function, but that's only because for now segmented
-// stacks are disabled.
-
-#[cfg(target_arch = "x86")]
-struct Registers {
-    eax: u32, ebx: u32, ecx: u32, edx: u32,
-    ebp: u32, esi: u32, edi: u32, esp: u32,
-    cs: u16, ds: u16, ss: u16, es: u16, fs: u16, gs: u16,
-    eflags: u32, eip: u32
-}
-
-#[cfg(target_arch = "x86")]
-fn new_regs() -> ~Registers {
-    ~Registers {
-        eax: 0, ebx: 0, ecx: 0, edx: 0,
-        ebp: 0, esi: 0, edi: 0, esp: 0,
-        cs: 0, ds: 0, ss: 0, es: 0, fs: 0, gs: 0,
-        eflags: 0, eip: 0
-    }
-}
-
-#[cfg(target_arch = "x86")]
-fn initialize_call_frame(regs: &mut Registers, fptr: *c_void, arg: *c_void,
-                         sp: *mut uint) {
-
-    let sp = align_down(sp);
-    let sp = mut_offset(sp, -4);
-
-    unsafe { *sp = arg as uint };
-    let sp = mut_offset(sp, -1);
-    unsafe { *sp = 0 }; // The final return address
-
-    regs.esp = sp as u32;
-    regs.eip = fptr as u32;
-
-    // Last base pointer on the stack is 0
-    regs.ebp = 0;
-}
-
-// windows requires saving more registers (both general and XMM), so the windows
-// register context must be larger.
-#[cfg(windows, target_arch = "x86_64")]
-type Registers = [uint, ..34];
-#[cfg(not(windows), target_arch = "x86_64")]
-type Registers = [uint, ..22];
-
-#[cfg(windows, target_arch = "x86_64")]
-fn new_regs() -> ~Registers { ~([0, .. 34]) }
-#[cfg(not(windows), target_arch = "x86_64")]
-fn new_regs() -> ~Registers { ~([0, .. 22]) }
-
-#[cfg(target_arch = "x86_64")]
-fn initialize_call_frame(regs: &mut Registers, fptr: *c_void, arg: *c_void,
-                         sp: *mut uint) {
-
-    // Redefinitions from rt/arch/x86_64/regs.h
-    static RUSTRT_ARG0: uint = 3;
-    static RUSTRT_RSP: uint = 1;
-    static RUSTRT_IP: uint = 8;
-    static RUSTRT_RBP: uint = 2;
-
-    let sp = align_down(sp);
-    let sp = mut_offset(sp, -1);
-
-    // The final return address. 0 indicates the bottom of the stack
-    unsafe { *sp = 0; }
-
-    rtdebug!("creating call frame");
-    rtdebug!("fptr {}", fptr);
-    rtdebug!("arg {}", arg);
-    rtdebug!("sp {}", sp);
-
-    regs[RUSTRT_ARG0] = arg as uint;
-    regs[RUSTRT_RSP] = sp as uint;
-    regs[RUSTRT_IP] = fptr as uint;
-
-    // Last base pointer on the stack should be 0
-    regs[RUSTRT_RBP] = 0;
-}
-
-#[cfg(target_arch = "arm")]
-type Registers = [uint, ..32];
-
-#[cfg(target_arch = "arm")]
-fn new_regs() -> ~Registers { ~([0, .. 32]) }
-
-#[cfg(target_arch = "arm")]
-fn initialize_call_frame(regs: &mut Registers, fptr: *c_void, arg: *c_void,
-                         sp: *mut uint) {
-    let sp = align_down(sp);
-    // sp of arm eabi is 8-byte aligned
-    let sp = mut_offset(sp, -2);
-
-    // The final return address. 0 indicates the bottom of the stack
-    unsafe { *sp = 0; }
-
-    regs[0] = arg as uint;   // r0
-    regs[13] = sp as uint;   // #53 sp, r13
-    regs[14] = fptr as uint; // #60 pc, r15 --> lr
-}
-
-#[cfg(target_arch = "mips")]
-type Registers = [uint, ..32];
-
-#[cfg(target_arch = "mips")]
-fn new_regs() -> ~Registers { ~([0, .. 32]) }
-
-#[cfg(target_arch = "mips")]
-fn initialize_call_frame(regs: &mut Registers, fptr: *c_void, arg: *c_void,
-                         sp: *mut uint) {
-    let sp = align_down(sp);
-    // sp of mips o32 is 8-byte aligned
-    let sp = mut_offset(sp, -2);
-
-    // The final return address. 0 indicates the bottom of the stack
-    unsafe { *sp = 0; }
-
-    regs[4] = arg as uint;
-    regs[29] = sp as uint;
-    regs[25] = fptr as uint;
-    regs[31] = fptr as uint;
-}
-
-fn align_down(sp: *mut uint) -> *mut uint {
-    unsafe {
-        let sp: uint = transmute(sp);
-        let sp = sp & !(16 - 1);
-        transmute::<uint, *mut uint>(sp)
-    }
-}
-
-// ptr::mut_offset is positive ints only
-#[inline]
-pub fn mut_offset<T>(ptr: *mut T, count: int) -> *mut T {
-    use mem::size_of;
-    (ptr as int + count * (size_of::<T>() as int)) as *mut T
-}
-
-#[inline(always)]
-pub unsafe fn record_stack_bounds(stack_lo: uint, stack_hi: uint) {
-    // When the old runtime had segmented stacks, it used a calculation that was
-    // "limit + RED_ZONE + FUDGE". The red zone was for things like dynamic
-    // symbol resolution, llvm function calls, etc. In theory this red zone
-    // value is 0, but it matters far less when we have gigantic stacks because
-    // we don't need to be so exact about our stack budget. The "fudge factor"
-    // was because LLVM doesn't emit a stack check for functions < 256 bytes in
-    // size. Again though, we have giant stacks, so we round all these
-    // calculations up to the nice round number of 20k.
-    record_sp_limit(stack_lo + RED_ZONE);
-
-    return target_record_stack_bounds(stack_lo, stack_hi);
-
-    #[cfg(not(windows))] #[cfg(not(target_arch = "x86_64"))] #[inline(always)]
-    unsafe fn target_record_stack_bounds(_stack_lo: uint, _stack_hi: uint) {}
-    #[cfg(windows, target_arch = "x86_64")] #[inline(always)]
-    unsafe fn target_record_stack_bounds(stack_lo: uint, stack_hi: uint) {
-        // Windows compiles C functions which may check the stack bounds. This
-        // means that if we want to perform valid FFI on windows, then we need
-        // to ensure that the stack bounds are what they truly are for this
-        // task. More info can be found at:
-        //   https://github.com/mozilla/rust/issues/3445#issuecomment-26114839
-        //
-        // stack range is at TIB: %gs:0x08 (top) and %gs:0x10 (bottom)
-        asm!("mov $0, %gs:0x08" :: "r"(stack_hi) :: "volatile");
-        asm!("mov $0, %gs:0x10" :: "r"(stack_lo) :: "volatile");
-    }
-}
-
-/// Records the current limit of the stack as specified by `end`.
-///
-/// This is stored in an OS-dependent location, likely inside of the thread
-/// local storage. The location that the limit is stored is a pre-ordained
-/// location because it's where LLVM has emitted code to check.
-///
-/// Note that this cannot be called under normal circumstances. This function is
-/// changing the stack limit, so upon returning any further function calls will
-/// possibly be triggering the morestack logic if you're not careful.
-///
-/// Also note that this and all of the inside functions are all flagged as
-/// "inline(always)" because they're messing around with the stack limits.  This
-/// would be unfortunate for the functions themselves to trigger a morestack
-/// invocation (if they were an actual function call).
-#[inline(always)]
-pub unsafe fn record_sp_limit(limit: uint) {
-    return target_record_sp_limit(limit);
-
-    // x86-64
-    #[cfg(target_arch = "x86_64", target_os = "macos")] #[inline(always)]
-    unsafe fn target_record_sp_limit(limit: uint) {
-        asm!("movq $$0x60+90*8, %rsi
-              movq $0, %gs:(%rsi)" :: "r"(limit) : "rsi" : "volatile")
-    }
-    #[cfg(target_arch = "x86_64", target_os = "linux")] #[inline(always)]
-    unsafe fn target_record_sp_limit(limit: uint) {
-        asm!("movq $0, %fs:112" :: "r"(limit) :: "volatile")
-    }
-    #[cfg(target_arch = "x86_64", target_os = "win32")] #[inline(always)]
-    unsafe fn target_record_sp_limit(limit: uint) {
-        // see: http://en.wikipedia.org/wiki/Win32_Thread_Information_Block
-        // store this inside of the "arbitrary data slot", but double the size
-        // because this is 64 bit instead of 32 bit
-        asm!("movq $0, %gs:0x28" :: "r"(limit) :: "volatile")
-    }
-    #[cfg(target_arch = "x86_64", target_os = "freebsd")] #[inline(always)]
-    unsafe fn target_record_sp_limit(limit: uint) {
-        asm!("movq $0, %fs:24" :: "r"(limit) :: "volatile")
-    }
-
-    // x86
-    #[cfg(target_arch = "x86", target_os = "macos")] #[inline(always)]
-    unsafe fn target_record_sp_limit(limit: uint) {
-        asm!("movl $$0x48+90*4, %eax
-              movl $0, %gs:(%eax)" :: "r"(limit) : "eax" : "volatile")
-    }
-    #[cfg(target_arch = "x86", target_os = "linux")]
-    #[cfg(target_arch = "x86", target_os = "freebsd")] #[inline(always)]
-    unsafe fn target_record_sp_limit(limit: uint) {
-        asm!("movl $0, %gs:48" :: "r"(limit) :: "volatile")
-    }
-    #[cfg(target_arch = "x86", target_os = "win32")] #[inline(always)]
-    unsafe fn target_record_sp_limit(limit: uint) {
-        // see: http://en.wikipedia.org/wiki/Win32_Thread_Information_Block
-        // store this inside of the "arbitrary data slot"
-        asm!("movl $0, %fs:0x14" :: "r"(limit) :: "volatile")
-    }
-
-    // mips, arm - Some brave soul can port these to inline asm, but it's over
-    //             my head personally
-    #[cfg(target_arch = "mips")]
-    #[cfg(target_arch = "arm")] #[inline(always)]
-    unsafe fn target_record_sp_limit(limit: uint) {
-        return record_sp_limit(limit as *c_void);
-        extern {
-            fn record_sp_limit(limit: *c_void);
-        }
-    }
-}
-
-/// The counterpart of the function above, this function will fetch the current
-/// stack limit stored in TLS.
-///
-/// Note that all of these functions are meant to be exact counterparts of their
-/// brethren above, except that the operands are reversed.
-///
-/// As with the setter, this function does not have a __morestack header and can
-/// therefore be called in a "we're out of stack" situation.
-#[inline(always)]
-// currently only called by `rust_stack_exhausted`, which doesn't
-// exist in a test build.
-#[cfg(not(test))]
-pub unsafe fn get_sp_limit() -> uint {
-    return target_get_sp_limit();
-
-    // x86-64
-    #[cfg(target_arch = "x86_64", target_os = "macos")] #[inline(always)]
-    unsafe fn target_get_sp_limit() -> uint {
-        let limit;
-        asm!("movq $$0x60+90*8, %rsi
-              movq %gs:(%rsi), $0" : "=r"(limit) :: "rsi" : "volatile");
-        return limit;
-    }
-    #[cfg(target_arch = "x86_64", target_os = "linux")] #[inline(always)]
-    unsafe fn target_get_sp_limit() -> uint {
-        let limit;
-        asm!("movq %fs:112, $0" : "=r"(limit) ::: "volatile");
-        return limit;
-    }
-    #[cfg(target_arch = "x86_64", target_os = "win32")] #[inline(always)]
-    unsafe fn target_get_sp_limit() -> uint {
-        let limit;
-        asm!("movq %gs:0x28, $0" : "=r"(limit) ::: "volatile");
-        return limit;
-    }
-    #[cfg(target_arch = "x86_64", target_os = "freebsd")] #[inline(always)]
-    unsafe fn target_get_sp_limit() -> uint {
-        let limit;
-        asm!("movq %fs:24, $0" : "=r"(limit) ::: "volatile");
-        return limit;
-    }
-
-    // x86
-    #[cfg(target_arch = "x86", target_os = "macos")] #[inline(always)]
-    unsafe fn target_get_sp_limit() -> uint {
-        let limit;
-        asm!("movl $$0x48+90*4, %eax
-              movl %gs:(%eax), $0" : "=r"(limit) :: "eax" : "volatile");
-        return limit;
-    }
-    #[cfg(target_arch = "x86", target_os = "linux")]
-    #[cfg(target_arch = "x86", target_os = "freebsd")] #[inline(always)]
-    unsafe fn target_get_sp_limit() -> uint {
-        let limit;
-        asm!("movl %gs:48, $0" : "=r"(limit) ::: "volatile");
-        return limit;
-    }
-    #[cfg(target_arch = "x86", target_os = "win32")] #[inline(always)]
-    unsafe fn target_get_sp_limit() -> uint {
-        let limit;
-        asm!("movl %fs:0x14, $0" : "=r"(limit) ::: "volatile");
-        return limit;
-    }
-
-    // mips, arm - Some brave soul can port these to inline asm, but it's over
-    //             my head personally
-    #[cfg(target_arch = "mips")]
-    #[cfg(target_arch = "arm")] #[inline(always)]
-    unsafe fn target_get_sp_limit() -> uint {
-        return get_sp_limit() as uint;
-        extern {
-            fn get_sp_limit() -> *c_void;
-        }
-    }
-}
diff --git a/src/libstd/rt/crate_map.rs b/src/libstd/rt/crate_map.rs
index 22fc3f0ab56..d9b40cfbb6e 100644
--- a/src/libstd/rt/crate_map.rs
+++ b/src/libstd/rt/crate_map.rs
@@ -30,7 +30,7 @@ pub struct CrateMap<'a> {
     version: i32,
     entries: &'a [ModEntry<'a>],
     children: &'a [&'a CrateMap<'a>],
-    event_loop_factory: Option<extern "C" fn() -> ~EventLoop>,
+    event_loop_factory: Option<fn() -> ~EventLoop>,
 }
 
 #[cfg(not(windows))]
diff --git a/src/libstd/rt/deque.rs b/src/libstd/rt/deque.rs
deleted file mode 100644
index 770fc9ffa12..00000000000
--- a/src/libstd/rt/deque.rs
+++ /dev/null
@@ -1,658 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! A (mostly) lock-free concurrent work-stealing deque
-//!
-//! This module contains an implementation of the Chase-Lev work stealing deque
-//! described in "Dynamic Circular Work-Stealing Deque". The implementation is
-//! heavily based on the pseudocode found in the paper.
-//!
-//! This implementation does not want to have the restriction of a garbage
-//! collector for reclamation of buffers, and instead it uses a shared pool of
-//! buffers. This shared pool is required for correctness in this
-//! implementation.
-//!
-//! The only lock-synchronized portions of this deque are the buffer allocation
-//! and deallocation portions. Otherwise all operations are lock-free.
-//!
-//! # Example
-//!
-//!     use std::rt::deque::BufferPool;
-//!
-//!     let mut pool = BufferPool::new();
-//!     let (mut worker, mut stealer) = pool.deque();
-//!
-//!     // Only the worker may push/pop
-//!     worker.push(1);
-//!     worker.pop();
-//!
-//!     // Stealers take data from the other end of the deque
-//!     worker.push(1);
-//!     stealer.steal();
-//!
-//!     // Stealers can be cloned to have many stealers stealing in parallel
-//!     worker.push(1);
-//!     let mut stealer2 = stealer.clone();
-//!     stealer2.steal();
-
-// NB: the "buffer pool" strategy is not done for speed, but rather for
-//     correctness. For more info, see the comment on `swap_buffer`
-
-// XXX: all atomic operations in this module use a SeqCst ordering. That is
-//      probably overkill
-
-use cast;
-use clone::Clone;
-use iter::range;
-use kinds::Send;
-use libc;
-use mem;
-use ops::Drop;
-use option::{Option, Some, None};
-use ptr;
-use unstable::atomics::{AtomicInt, AtomicPtr, SeqCst};
-use unstable::sync::{UnsafeArc, Exclusive};
-
-// Once the queue is less than 1/K full, then it will be downsized. Note that
-// the deque requires that this number be less than 2.
-static K: int = 4;
-
-// Minimum number of bits that a buffer size should be. No buffer will resize to
-// under this value, and all deques will initially contain a buffer of this
-// size.
-//
-// The size in question is 1 << MIN_BITS
-static MIN_BITS: int = 7;
-
-struct Deque<T> {
-    bottom: AtomicInt,
-    top: AtomicInt,
-    array: AtomicPtr<Buffer<T>>,
-    pool: BufferPool<T>,
-}
-
-/// Worker half of the work-stealing deque. This worker has exclusive access to
-/// one side of the deque, and uses `push` and `pop` method to manipulate it.
-///
-/// There may only be one worker per deque.
-pub struct Worker<T> {
-    priv deque: UnsafeArc<Deque<T>>,
-}
-
-/// The stealing half of the work-stealing deque. Stealers have access to the
-/// opposite end of the deque from the worker, and they only have access to the
-/// `steal` method.
-pub struct Stealer<T> {
-    priv deque: UnsafeArc<Deque<T>>,
-}
-
-/// When stealing some data, this is an enumeration of the possible outcomes.
-#[deriving(Eq)]
-pub enum Stolen<T> {
-    /// The deque was empty at the time of stealing
-    Empty,
-    /// The stealer lost the race for stealing data, and a retry may return more
-    /// data.
-    Abort,
-    /// The stealer has successfully stolen some data.
-    Data(T),
-}
-
-/// The allocation pool for buffers used by work-stealing deques. Right now this
-/// structure is used for reclamation of memory after it is no longer in use by
-/// deques.
-///
-/// This data structure is protected by a mutex, but it is rarely used. Deques
-/// will only use this structure when allocating a new buffer or deallocating a
-/// previous one.
-pub struct BufferPool<T> {
-    priv pool: Exclusive<~[~Buffer<T>]>,
-}
-
-/// An internal buffer used by the chase-lev deque. This structure is actually
-/// implemented as a circular buffer, and is used as the intermediate storage of
-/// the data in the deque.
-///
-/// This type is implemented with *T instead of ~[T] for two reasons:
-///
-///   1. There is nothing safe about using this buffer. This easily allows the
-///      same value to be read twice in to rust, and there is nothing to
-///      prevent this. The usage by the deque must ensure that one of the
-///      values is forgotten. Furthermore, we only ever want to manually run
-///      destructors for values in this buffer (on drop) because the bounds
-///      are defined by the deque it's owned by.
-///
-///   2. We can certainly avoid bounds checks using *T instead of ~[T], although
-///      LLVM is probably pretty good at doing this already.
-struct Buffer<T> {
-    storage: *T,
-    log_size: int,
-}
-
-impl<T: Send> BufferPool<T> {
-    /// Allocates a new buffer pool which in turn can be used to allocate new
-    /// deques.
-    pub fn new() -> BufferPool<T> {
-        BufferPool { pool: Exclusive::new(~[]) }
-    }
-
-    /// Allocates a new work-stealing deque which will send/receiving memory to
-    /// and from this buffer pool.
-    pub fn deque(&mut self) -> (Worker<T>, Stealer<T>) {
-        let (a, b) = UnsafeArc::new2(Deque::new(self.clone()));
-        (Worker { deque: a }, Stealer { deque: b })
-    }
-
-    fn alloc(&mut self, bits: int) -> ~Buffer<T> {
-        unsafe {
-            self.pool.with(|pool| {
-                match pool.iter().position(|x| x.size() >= (1 << bits)) {
-                    Some(i) => pool.remove(i),
-                    None => ~Buffer::new(bits)
-                }
-            })
-        }
-    }
-
-    fn free(&mut self, buf: ~Buffer<T>) {
-        unsafe {
-            let mut buf = Some(buf);
-            self.pool.with(|pool| {
-                let buf = buf.take_unwrap();
-                match pool.iter().position(|v| v.size() > buf.size()) {
-                    Some(i) => pool.insert(i, buf),
-                    None => pool.push(buf),
-                }
-            })
-        }
-    }
-}
-
-impl<T: Send> Clone for BufferPool<T> {
-    fn clone(&self) -> BufferPool<T> { BufferPool { pool: self.pool.clone() } }
-}
-
-impl<T: Send> Worker<T> {
-    /// Pushes data onto the front of this work queue.
-    pub fn push(&mut self, t: T) {
-        unsafe { (*self.deque.get()).push(t) }
-    }
-    /// Pops data off the front of the work queue, returning `None` on an empty
-    /// queue.
-    pub fn pop(&mut self) -> Option<T> {
-        unsafe { (*self.deque.get()).pop() }
-    }
-
-    /// Gets access to the buffer pool that this worker is attached to. This can
-    /// be used to create more deques which share the same buffer pool as this
-    /// deque.
-    pub fn pool<'a>(&'a mut self) -> &'a mut BufferPool<T> {
-        unsafe { &mut (*self.deque.get()).pool }
-    }
-}
-
-impl<T: Send> Stealer<T> {
-    /// Steals work off the end of the queue (opposite of the worker's end)
-    pub fn steal(&mut self) -> Stolen<T> {
-        unsafe { (*self.deque.get()).steal() }
-    }
-
-    /// Gets access to the buffer pool that this stealer is attached to. This
-    /// can be used to create more deques which share the same buffer pool as
-    /// this deque.
-    pub fn pool<'a>(&'a mut self) -> &'a mut BufferPool<T> {
-        unsafe { &mut (*self.deque.get()).pool }
-    }
-}
-
-impl<T: Send> Clone for Stealer<T> {
-    fn clone(&self) -> Stealer<T> { Stealer { deque: self.deque.clone() } }
-}
-
-// Almost all of this code can be found directly in the paper so I'm not
-// personally going to heavily comment what's going on here.
-
-impl<T: Send> Deque<T> {
-    fn new(mut pool: BufferPool<T>) -> Deque<T> {
-        let buf = pool.alloc(MIN_BITS);
-        Deque {
-            bottom: AtomicInt::new(0),
-            top: AtomicInt::new(0),
-            array: AtomicPtr::new(unsafe { cast::transmute(buf) }),
-            pool: pool,
-        }
-    }
-
-    unsafe fn push(&mut self, data: T) {
-        let mut b = self.bottom.load(SeqCst);
-        let t = self.top.load(SeqCst);
-        let mut a = self.array.load(SeqCst);
-        let size = b - t;
-        if size >= (*a).size() - 1 {
-            // You won't find this code in the chase-lev deque paper. This is
-            // alluded to in a small footnote, however. We always free a buffer
-            // when growing in order to prevent leaks.
-            a = self.swap_buffer(b, a, (*a).resize(b, t, 1));
-            b = self.bottom.load(SeqCst);
-        }
-        (*a).put(b, data);
-        self.bottom.store(b + 1, SeqCst);
-    }
-
-    unsafe fn pop(&mut self) -> Option<T> {
-        let b = self.bottom.load(SeqCst);
-        let a = self.array.load(SeqCst);
-        let b = b - 1;
-        self.bottom.store(b, SeqCst);
-        let t = self.top.load(SeqCst);
-        let size = b - t;
-        if size < 0 {
-            self.bottom.store(t, SeqCst);
-            return None;
-        }
-        let data = (*a).get(b);
-        if size > 0 {
-            self.maybe_shrink(b, t);
-            return Some(data);
-        }
-        if self.top.compare_and_swap(t, t + 1, SeqCst) == t {
-            self.bottom.store(t + 1, SeqCst);
-            return Some(data);
-        } else {
-            self.bottom.store(t + 1, SeqCst);
-            cast::forget(data); // someone else stole this value
-            return None;
-        }
-    }
-
-    unsafe fn steal(&mut self) -> Stolen<T> {
-        let t = self.top.load(SeqCst);
-        let old = self.array.load(SeqCst);
-        let b = self.bottom.load(SeqCst);
-        let a = self.array.load(SeqCst);
-        let size = b - t;
-        if size <= 0 { return Empty }
-        if size % (*a).size() == 0 {
-            if a == old && t == self.top.load(SeqCst) {
-                return Empty
-            }
-            return Abort
-        }
-        let data = (*a).get(t);
-        if self.top.compare_and_swap(t, t + 1, SeqCst) == t {
-            Data(data)
-        } else {
-            cast::forget(data); // someone else stole this value
-            Abort
-        }
-    }
-
-    unsafe fn maybe_shrink(&mut self, b: int, t: int) {
-        let a = self.array.load(SeqCst);
-        if b - t < (*a).size() / K && b - t > (1 << MIN_BITS) {
-            self.swap_buffer(b, a, (*a).resize(b, t, -1));
-        }
-    }
-
-    // Helper routine not mentioned in the paper which is used in growing and
-    // shrinking buffers to swap in a new buffer into place. As a bit of a
-    // recap, the whole point that we need a buffer pool rather than just
-    // calling malloc/free directly is that stealers can continue using buffers
-    // after this method has called 'free' on it. The continued usage is simply
-    // a read followed by a forget, but we must make sure that the memory can
-    // continue to be read after we flag this buffer for reclamation.
-    unsafe fn swap_buffer(&mut self, b: int, old: *mut Buffer<T>,
-                          buf: Buffer<T>) -> *mut Buffer<T> {
-        let newbuf: *mut Buffer<T> = cast::transmute(~buf);
-        self.array.store(newbuf, SeqCst);
-        let ss = (*newbuf).size();
-        self.bottom.store(b + ss, SeqCst);
-        let t = self.top.load(SeqCst);
-        if self.top.compare_and_swap(t, t + ss, SeqCst) != t {
-            self.bottom.store(b, SeqCst);
-        }
-        self.pool.free(cast::transmute(old));
-        return newbuf;
-    }
-}
-
-
-#[unsafe_destructor]
-impl<T: Send> Drop for Deque<T> {
-    fn drop(&mut self) {
-        let t = self.top.load(SeqCst);
-        let b = self.bottom.load(SeqCst);
-        let a = self.array.load(SeqCst);
-        // Free whatever is leftover in the dequeue, and then move the buffer
-        // back into the pool.
-        for i in range(t, b) {
-            let _: T = unsafe { (*a).get(i) };
-        }
-        self.pool.free(unsafe { cast::transmute(a) });
-    }
-}
-
-impl<T: Send> Buffer<T> {
-    unsafe fn new(log_size: int) -> Buffer<T> {
-        let size = (1 << log_size) * mem::size_of::<T>();
-        let buffer = libc::malloc(size as libc::size_t);
-        assert!(!buffer.is_null());
-        Buffer {
-            storage: buffer as *T,
-            log_size: log_size,
-        }
-    }
-
-    fn size(&self) -> int { 1 << self.log_size }
-
-    // Apparently LLVM cannot optimize (foo % (1 << bar)) into this implicitly
-    fn mask(&self) -> int { (1 << self.log_size) - 1 }
-
-    // This does not protect against loading duplicate values of the same cell,
-    // nor does this clear out the contents contained within. Hence, this is a
-    // very unsafe method which the caller needs to treat specially in case a
-    // race is lost.
-    unsafe fn get(&self, i: int) -> T {
-        ptr::read_ptr(self.storage.offset(i & self.mask()))
-    }
-
-    // Unsafe because this unsafely overwrites possibly uninitialized or
-    // initialized data.
-    unsafe fn put(&mut self, i: int, t: T) {
-        let ptr = self.storage.offset(i & self.mask());
-        ptr::copy_nonoverlapping_memory(ptr as *mut T, &t as *T, 1);
-        cast::forget(t);
-    }
-
-    // Again, unsafe because this has incredibly dubious ownership violations.
-    // It is assumed that this buffer is immediately dropped.
-    unsafe fn resize(&self, b: int, t: int, delta: int) -> Buffer<T> {
-        let mut buf = Buffer::new(self.log_size + delta);
-        for i in range(t, b) {
-            buf.put(i, self.get(i));
-        }
-        return buf;
-    }
-}
-
-#[unsafe_destructor]
-impl<T: Send> Drop for Buffer<T> {
-    fn drop(&mut self) {
-        // It is assumed that all buffers are empty on drop.
-        unsafe { libc::free(self.storage as *libc::c_void) }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use prelude::*;
-    use super::{Data, BufferPool, Abort, Empty, Worker, Stealer};
-
-    use cast;
-    use rt::thread::Thread;
-    use rand;
-    use rand::Rng;
-    use unstable::atomics::{AtomicBool, INIT_ATOMIC_BOOL, SeqCst,
-                            AtomicUint, INIT_ATOMIC_UINT};
-    use vec;
-
-    #[test]
-    fn smoke() {
-        let mut pool = BufferPool::new();
-        let (mut w, mut s) = pool.deque();
-        assert_eq!(w.pop(), None);
-        assert_eq!(s.steal(), Empty);
-        w.push(1);
-        assert_eq!(w.pop(), Some(1));
-        w.push(1);
-        assert_eq!(s.steal(), Data(1));
-        w.push(1);
-        assert_eq!(s.clone().steal(), Data(1));
-    }
-
-    #[test]
-    fn stealpush() {
-        static AMT: int = 100000;
-        let mut pool = BufferPool::<int>::new();
-        let (mut w, s) = pool.deque();
-        let t = do Thread::start {
-            let mut s = s;
-            let mut left = AMT;
-            while left > 0 {
-                match s.steal() {
-                    Data(i) => {
-                        assert_eq!(i, 1);
-                        left -= 1;
-                    }
-                    Abort | Empty => {}
-                }
-            }
-        };
-
-        for _ in range(0, AMT) {
-            w.push(1);
-        }
-
-        t.join();
-    }
-
-    #[test]
-    fn stealpush_large() {
-        static AMT: int = 100000;
-        let mut pool = BufferPool::<(int, int)>::new();
-        let (mut w, s) = pool.deque();
-        let t = do Thread::start {
-            let mut s = s;
-            let mut left = AMT;
-            while left > 0 {
-                match s.steal() {
-                    Data((1, 10)) => { left -= 1; }
-                    Data(..) => fail!(),
-                    Abort | Empty => {}
-                }
-            }
-        };
-
-        for _ in range(0, AMT) {
-            w.push((1, 10));
-        }
-
-        t.join();
-    }
-
-    fn stampede(mut w: Worker<~int>, s: Stealer<~int>,
-                nthreads: int, amt: uint) {
-        for _ in range(0, amt) {
-            w.push(~20);
-        }
-        let mut remaining = AtomicUint::new(amt);
-        let unsafe_remaining: *mut AtomicUint = &mut remaining;
-
-        let threads = range(0, nthreads).map(|_| {
-            let s = s.clone();
-            do Thread::start {
-                unsafe {
-                    let mut s = s;
-                    while (*unsafe_remaining).load(SeqCst) > 0 {
-                        match s.steal() {
-                            Data(~20) => {
-                                (*unsafe_remaining).fetch_sub(1, SeqCst);
-                            }
-                            Data(..) => fail!(),
-                            Abort | Empty => {}
-                        }
-                    }
-                }
-            }
-        }).to_owned_vec();
-
-        while remaining.load(SeqCst) > 0 {
-            match w.pop() {
-                Some(~20) => { remaining.fetch_sub(1, SeqCst); }
-                Some(..) => fail!(),
-                None => {}
-            }
-        }
-
-        for thread in threads.move_iter() {
-            thread.join();
-        }
-    }
-
-    #[test]
-    fn run_stampede() {
-        let mut pool = BufferPool::<~int>::new();
-        let (w, s) = pool.deque();
-        stampede(w, s, 8, 10000);
-    }
-
-    #[test]
-    fn many_stampede() {
-        static AMT: uint = 4;
-        let mut pool = BufferPool::<~int>::new();
-        let threads = range(0, AMT).map(|_| {
-            let (w, s) = pool.deque();
-            do Thread::start {
-                stampede(w, s, 4, 10000);
-            }
-        }).to_owned_vec();
-
-        for thread in threads.move_iter() {
-            thread.join();
-        }
-    }
-
-    #[test]
-    fn stress() {
-        static AMT: int = 100000;
-        static NTHREADS: int = 8;
-        static mut DONE: AtomicBool = INIT_ATOMIC_BOOL;
-        static mut HITS: AtomicUint = INIT_ATOMIC_UINT;
-        let mut pool = BufferPool::<int>::new();
-        let (mut w, s) = pool.deque();
-
-        let threads = range(0, NTHREADS).map(|_| {
-            let s = s.clone();
-            do Thread::start {
-                unsafe {
-                    let mut s = s;
-                    loop {
-                        match s.steal() {
-                            Data(2) => { HITS.fetch_add(1, SeqCst); }
-                            Data(..) => fail!(),
-                            _ if DONE.load(SeqCst) => break,
-                            _ => {}
-                        }
-                    }
-                }
-            }
-        }).to_owned_vec();
-
-        let mut rng = rand::task_rng();
-        let mut expected = 0;
-        while expected < AMT {
-            if rng.gen_range(0, 3) == 2 {
-                match w.pop() {
-                    None => {}
-                    Some(2) => unsafe { HITS.fetch_add(1, SeqCst); },
-                    Some(_) => fail!(),
-                }
-            } else {
-                expected += 1;
-                w.push(2);
-            }
-        }
-
-        unsafe {
-            while HITS.load(SeqCst) < AMT as uint {
-                match w.pop() {
-                    None => {}
-                    Some(2) => { HITS.fetch_add(1, SeqCst); },
-                    Some(_) => fail!(),
-                }
-            }
-            DONE.store(true, SeqCst);
-        }
-
-        for thread in threads.move_iter() {
-            thread.join();
-        }
-
-        assert_eq!(unsafe { HITS.load(SeqCst) }, expected as uint);
-    }
-
-    #[test]
-    #[ignore(cfg(windows))] // apparently windows scheduling is weird?
-    fn no_starvation() {
-        static AMT: int = 10000;
-        static NTHREADS: int = 4;
-        static mut DONE: AtomicBool = INIT_ATOMIC_BOOL;
-        let mut pool = BufferPool::<(int, uint)>::new();
-        let (mut w, s) = pool.deque();
-
-        let (threads, hits) = vec::unzip(range(0, NTHREADS).map(|_| {
-            let s = s.clone();
-            let unique_box = ~AtomicUint::new(0);
-            let thread_box = unsafe {
-                *cast::transmute::<&~AtomicUint,**mut AtomicUint>(&unique_box)
-            };
-            (do Thread::start {
-                unsafe {
-                    let mut s = s;
-                    loop {
-                        match s.steal() {
-                            Data((1, 2)) => {
-                                (*thread_box).fetch_add(1, SeqCst);
-                            }
-                            Data(..) => fail!(),
-                            _ if DONE.load(SeqCst) => break,
-                            _ => {}
-                        }
-                    }
-                }
-            }, unique_box)
-        }));
-
-        let mut rng = rand::task_rng();
-        let mut myhit = false;
-        let mut iter = 0;
-        'outer: loop {
-            for _ in range(0, rng.gen_range(0, AMT)) {
-                if !myhit && rng.gen_range(0, 3) == 2 {
-                    match w.pop() {
-                        None => {}
-                        Some((1, 2)) => myhit = true,
-                        Some(_) => fail!(),
-                    }
-                } else {
-                    w.push((1, 2));
-                }
-            }
-            iter += 1;
-
-            debug!("loop iteration {}", iter);
-            for (i, slot) in hits.iter().enumerate() {
-                let amt = slot.load(SeqCst);
-                debug!("thread {}: {}", i, amt);
-                if amt == 0 { continue 'outer; }
-            }
-            if myhit {
-                break
-            }
-        }
-
-        unsafe { DONE.store(true, SeqCst); }
-
-        for thread in threads.move_iter() {
-            thread.join();
-        }
-    }
-}
-
diff --git a/src/libstd/rt/env.rs b/src/libstd/rt/env.rs
index d1bd450afe2..f3fa482b18c 100644
--- a/src/libstd/rt/env.rs
+++ b/src/libstd/rt/env.rs
@@ -17,7 +17,7 @@ use os;
 // Note that these are all accessed without any synchronization.
 // They are expected to be initialized once then left alone.
 
-static mut MIN_STACK: uint = 2000000;
+static mut MIN_STACK: uint = 2 * 1024 * 1024;
 static mut DEBUG_BORROW: bool = false;
 static mut POISON_ON_FREE: bool = false;
 
diff --git a/src/libstd/rt/kill.rs b/src/libstd/rt/kill.rs
deleted file mode 100644
index f4f128cf5aa..00000000000
--- a/src/libstd/rt/kill.rs
+++ /dev/null
@@ -1,318 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-/*!
-
-Task death: asynchronous killing, linked failure, exit code propagation.
-
-This file implements two orthogonal building-blocks for communicating failure
-between tasks. One is 'linked failure' or 'task killing', that is, a failing
-task causing other tasks to fail promptly (even those that are blocked on
-pipes or I/O). The other is 'exit code propagation', which affects the result
-observed by the parent of a task::try task that itself spawns child tasks
-(such as any #[test] function). In both cases the data structures live in
-KillHandle.
-
-
-I. Task killing.
-
-The model for killing involves two atomic flags, the "kill flag" and the
-"unkillable flag". Operations on the kill flag include:
-
-- In the taskgroup code (task/spawn.rs), tasks store a clone of their
-  KillHandle in their shared taskgroup. Another task in the group that fails
-  will use that handle to call kill().
-- When a task blocks, it turns its ~Task into a BlockedTask by storing a
-  the transmuted ~Task pointer inside the KillHandle's kill flag. A task
-  trying to block and a task trying to kill it can simultaneously access the
-  kill flag, after which the task will get scheduled and fail (no matter who
-  wins the race). Likewise, a task trying to wake a blocked task normally and
-  a task trying to kill it can simultaneously access the flag; only one will
-  get the task to reschedule it.
-
-Operations on the unkillable flag include:
-
-- When a task becomes unkillable, it swaps on the flag to forbid any killer
-  from waking it up while it's blocked inside the unkillable section. If a
-  kill was already pending, the task fails instead of becoming unkillable.
-- When a task is done being unkillable, it restores the flag to the normal
-  running state. If a kill was received-but-blocked during the unkillable
-  section, the task fails at this later point.
-- When a task tries to kill another task, before swapping on the kill flag, it
-  first swaps on the unkillable flag, to see if it's "allowed" to wake up the
-  task. If it isn't, the killed task will receive the signal when it becomes
-  killable again. (Of course, a task trying to wake the task normally (e.g.
-  sending on a channel) does not access the unkillable flag at all.)
-
-Why do we not need acquire/release barriers on any of the kill flag swaps?
-This is because barriers establish orderings between accesses on different
-memory locations, but each kill-related operation is only a swap on a single
-location, so atomicity is all that matters. The exception is kill(), which
-does a swap on both flags in sequence. kill() needs no barriers because it
-does not matter if its two accesses are seen reordered on another CPU: if a
-killer does perform both writes, it means it saw a KILL_RUNNING in the
-unkillable flag, which means an unkillable task will see KILL_KILLED and fail
-immediately (rendering the subsequent write to the kill flag unnecessary).
-
-
-II. Exit code propagation.
-
-The basic model for exit code propagation, which is used with the "watched"
-spawn mode (on by default for linked spawns, off for supervised and unlinked
-spawns), is that a parent will wait for all its watched children to exit
-before reporting whether it succeeded or failed. A watching parent will only
-report success if it succeeded and all its children also reported success;
-otherwise, it will report failure. This is most useful for writing test cases:
-
- ```
-#[test]
-fn test_something_in_another_task {
-    do spawn {
-        assert!(collatz_conjecture_is_false());
-    }
-}
- ```
-
-Here, as the child task will certainly outlive the parent task, we might miss
-the failure of the child when deciding whether or not the test case passed.
-The watched spawn mode avoids this problem.
-
-In order to propagate exit codes from children to their parents, any
-'watching' parent must wait for all of its children to exit before it can
-report its final exit status. We achieve this by using an UnsafeArc, using the
-reference counting to track how many children are still alive, and using the
-unwrap() operation in the parent's exit path to wait for all children to exit.
-The UnsafeArc referred to here is actually the KillHandle itself.
-
-This also works transitively, as if a "middle" watched child task is itself
-watching a grandchild task, the "middle" task will do unwrap() on its own
-KillHandle (thereby waiting for the grandchild to exit) before dropping its
-reference to its watching parent (which will alert the parent).
-
-While UnsafeArc::unwrap() accomplishes the synchronization, there remains the
-matter of reporting the exit codes themselves. This is easiest when an exiting
-watched task has no watched children of its own:
-
-- If the task with no watched children exits successfully, it need do nothing.
-- If the task with no watched children has failed, it sets a flag in the
-  parent's KillHandle ("any_child_failed") to false. It then stays false forever.
-
-However, if a "middle" watched task with watched children of its own exits
-before its child exits, we need to ensure that the grandparent task may still
-see a failure from the grandchild task. While we could achieve this by having
-each intermediate task block on its handle, this keeps around the other resources
-the task was using. To be more efficient, this is accomplished via "tombstones".
-
-A tombstone is a closure, proc() -> bool, which will perform any waiting necessary
-to collect the exit code of descendant tasks. In its environment is captured
-the KillHandle of whichever task created the tombstone, and perhaps also any
-tombstones that that task itself had, and finally also another tombstone,
-effectively creating a lazy-list of heap closures.
-
-When a child wishes to exit early and leave tombstones behind for its parent,
-it must use a LittleLock (pthread mutex) to synchronize with any possible
-sibling tasks which are trying to do the same thing with the same parent.
-However, on the other side, when the parent is ready to pull on the tombstones,
-it need not use this lock, because the unwrap() serves as a barrier that ensures
-no children will remain with references to the handle.
-
-The main logic for creating and assigning tombstones can be found in the
-function reparent_children_to() in the impl for KillHandle.
-
-
-IIA. Issues with exit code propagation.
-
-There are two known issues with the current scheme for exit code propagation.
-
-- As documented in issue #8136, the structure mandates the possibility for stack
-  overflow when collecting tombstones that are very deeply nested. This cannot
-  be avoided with the closure representation, as tombstones end up structured in
-  a sort of tree. However, notably, the tombstones do not actually need to be
-  collected in any particular order, and so a doubly-linked list may be used.
-  However we do not do this yet because DList is in libextra.
-
-- A discussion with Graydon made me realize that if we decoupled the exit code
-  propagation from the parents-waiting action, this could result in a simpler
-  implementation as the exit codes themselves would not have to be propagated,
-  and could instead be propagated implicitly through the taskgroup mechanism
-  that we already have. The tombstoning scheme would still be required. I have
-  not implemented this because currently we can't receive a linked failure kill
-  signal during the task cleanup activity, as that is currently "unkillable",
-  and occurs outside the task's unwinder's "try" block, so would require some
-  restructuring.
-
-*/
-
-use cast;
-use option::{Option, Some, None};
-use prelude::*;
-use iter;
-use task::TaskResult;
-use rt::task::Task;
-use unstable::atomics::{AtomicUint, SeqCst};
-use unstable::sync::UnsafeArc;
-
-/// A handle to a blocked task. Usually this means having the ~Task pointer by
-/// ownership, but if the task is killable, a killer can steal it at any time.
-pub enum BlockedTask {
-    Owned(~Task),
-    Shared(UnsafeArc<AtomicUint>),
-}
-
-/// Per-task state related to task death, killing, failure, etc.
-pub struct Death {
-    // Action to be done with the exit code. If set, also makes the task wait
-    // until all its watched children exit before collecting the status.
-    on_exit:         Option<proc(TaskResult)>,
-    // nesting level counter for unstable::atomically calls (0 == can deschedule).
-    priv wont_sleep:      int,
-}
-
-pub struct BlockedTaskIterator {
-    priv inner: UnsafeArc<AtomicUint>,
-}
-
-impl Iterator<BlockedTask> for BlockedTaskIterator {
-    fn next(&mut self) -> Option<BlockedTask> {
-        Some(Shared(self.inner.clone()))
-    }
-}
-
-impl BlockedTask {
-    /// Returns Some if the task was successfully woken; None if already killed.
-    pub fn wake(self) -> Option<~Task> {
-        match self {
-            Owned(task) => Some(task),
-            Shared(arc) => unsafe {
-                match (*arc.get()).swap(0, SeqCst) {
-                    0 => None,
-                    n => cast::transmute(n),
-                }
-            }
-        }
-    }
-
-    /// Create a blocked task, unless the task was already killed.
-    pub fn block(task: ~Task) -> BlockedTask {
-        Owned(task)
-    }
-
-    /// Converts one blocked task handle to a list of many handles to the same.
-    pub fn make_selectable(self, num_handles: uint)
-        -> iter::Take<BlockedTaskIterator>
-    {
-        let arc = match self {
-            Owned(task) => {
-                let flag = unsafe { AtomicUint::new(cast::transmute(task)) };
-                UnsafeArc::new(flag)
-            }
-            Shared(arc) => arc.clone(),
-        };
-        BlockedTaskIterator{ inner: arc }.take(num_handles)
-    }
-
-    // This assertion has two flavours because the wake involves an atomic op.
-    // In the faster version, destructors will fail dramatically instead.
-    #[inline] #[cfg(not(test))]
-    pub fn assert_already_awake(self) { }
-    #[inline] #[cfg(test)]
-    pub fn assert_already_awake(self) { assert!(self.wake().is_none()); }
-
-    /// Convert to an unsafe uint value. Useful for storing in a pipe's state flag.
-    #[inline]
-    pub unsafe fn cast_to_uint(self) -> uint {
-        match self {
-            Owned(task) => {
-                let blocked_task_ptr: uint = cast::transmute(task);
-                rtassert!(blocked_task_ptr & 0x1 == 0);
-                blocked_task_ptr
-            }
-            Shared(arc) => {
-                let blocked_task_ptr: uint = cast::transmute(~arc);
-                rtassert!(blocked_task_ptr & 0x1 == 0);
-                blocked_task_ptr | 0x1
-            }
-        }
-    }
-
-    /// Convert from an unsafe uint value. Useful for retrieving a pipe's state flag.
-    #[inline]
-    pub unsafe fn cast_from_uint(blocked_task_ptr: uint) -> BlockedTask {
-        if blocked_task_ptr & 0x1 == 0 {
-            Owned(cast::transmute(blocked_task_ptr))
-        } else {
-            let ptr: ~UnsafeArc<AtomicUint> = cast::transmute(blocked_task_ptr & !1);
-            Shared(*ptr)
-        }
-    }
-}
-
-impl Death {
-    pub fn new() -> Death {
-        Death {
-            on_exit:         None,
-            wont_sleep:      0,
-        }
-    }
-
-    /// Collect failure exit codes from children and propagate them to a parent.
-    pub fn collect_failure(&mut self, result: TaskResult) {
-        match self.on_exit.take() {
-            Some(f) => f(result),
-            None => {}
-        }
-    }
-
-    /// Enter a possibly-nested "atomic" section of code. Just for assertions.
-    /// All calls must be paired with a subsequent call to allow_deschedule.
-    #[inline]
-    pub fn inhibit_deschedule(&mut self) {
-        self.wont_sleep += 1;
-    }
-
-    /// Exit a possibly-nested "atomic" section of code. Just for assertions.
-    /// All calls must be paired with a preceding call to inhibit_deschedule.
-    #[inline]
-    pub fn allow_deschedule(&mut self) {
-        rtassert!(self.wont_sleep != 0);
-        self.wont_sleep -= 1;
-    }
-
-    /// Ensure that the task is allowed to become descheduled.
-    #[inline]
-    pub fn assert_may_sleep(&self) {
-        if self.wont_sleep != 0 {
-            rtabort!("illegal atomic-sleep: attempt to reschedule while \
-                      using an Exclusive or LittleLock");
-        }
-    }
-}
-
-impl Drop for Death {
-    fn drop(&mut self) {
-        // Mustn't be in an atomic or unkillable section at task death.
-        rtassert!(self.wont_sleep == 0);
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use rt::test::*;
-    use super::*;
-
-    // Task blocking tests
-
-    #[test]
-    fn block_and_wake() {
-        do with_test_task |task| {
-            BlockedTask::block(task).wake().unwrap()
-        }
-    }
-}
diff --git a/src/libstd/rt/local.rs b/src/libstd/rt/local.rs
index d73ad98a25b..1c04b6b43ce 100644
--- a/src/libstd/rt/local.rs
+++ b/src/libstd/rt/local.rs
@@ -8,8 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use option::{Option, Some, None};
-use rt::sched::Scheduler;
+use option::Option;
 use rt::task::Task;
 use rt::local_ptr;
 
@@ -46,87 +45,10 @@ impl Local<local_ptr::Borrowed<Task>> for Task {
     }
 }
 
-/// Encapsulates a temporarily-borrowed scheduler.
-pub struct BorrowedScheduler {
-    priv task: local_ptr::Borrowed<Task>,
-}
-
-impl BorrowedScheduler {
-    fn new(mut task: local_ptr::Borrowed<Task>) -> BorrowedScheduler {
-        if task.get().sched.is_none() {
-            rtabort!("no scheduler")
-        } else {
-            BorrowedScheduler {
-                task: task,
-            }
-        }
-    }
-
-    #[inline]
-    pub fn get<'a>(&'a mut self) -> &'a mut ~Scheduler {
-        match self.task.get().sched {
-            None => rtabort!("no scheduler"),
-            Some(ref mut sched) => sched,
-        }
-    }
-}
-
-impl Local<BorrowedScheduler> for Scheduler {
-    fn put(value: ~Scheduler) {
-        let mut task = Local::borrow(None::<Task>);
-        task.get().sched = Some(value);
-    }
-    #[inline]
-    fn take() -> ~Scheduler {
-        unsafe {
-            // XXX: Unsafe for speed
-            let task: *mut Task = Local::unsafe_borrow();
-            (*task).sched.take_unwrap()
-        }
-    }
-    fn exists(_: Option<Scheduler>) -> bool {
-        let mut task = Local::borrow(None::<Task>);
-        task.get().sched.is_some()
-    }
-    #[inline]
-    fn borrow(_: Option<Scheduler>) -> BorrowedScheduler {
-        BorrowedScheduler::new(Local::borrow(None::<Task>))
-    }
-    unsafe fn unsafe_take() -> ~Scheduler { rtabort!("unimpl") }
-    unsafe fn unsafe_borrow() -> *mut Scheduler {
-        let task: *mut Task = Local::unsafe_borrow();
-        match (*task).sched {
-            Some(~ref mut sched) => {
-                let s: *mut Scheduler = &mut *sched;
-                return s;
-            }
-            None => {
-                rtabort!("no scheduler")
-            }
-        }
-    }
-    unsafe fn try_unsafe_borrow() -> Option<*mut Scheduler> {
-        let task_opt: Option<*mut Task> = Local::try_unsafe_borrow();
-        match task_opt {
-            Some(task) => {
-                match (*task).sched {
-                    Some(~ref mut sched) => {
-                        let s: *mut Scheduler = &mut *sched;
-                        Some(s)
-                    }
-                    None => None
-                }
-            }
-            None => None
-        }
-    }
-}
-
 #[cfg(test)]
 mod test {
     use option::None;
     use unstable::run_in_bare_thread;
-    use rt::test::*;
     use super::*;
     use rt::task::Task;
     use rt::local_ptr;
@@ -135,8 +57,7 @@ mod test {
     fn thread_local_task_smoke_test() {
         do run_in_bare_thread {
             local_ptr::init();
-            let mut sched = ~new_test_uv_sched();
-            let task = ~Task::new_root(&mut sched.stack_pool, None, proc(){});
+            let task = ~Task::new();
             Local::put(task);
             let task: ~Task = Local::take();
             cleanup_task(task);
@@ -147,12 +68,11 @@ mod test {
     fn thread_local_task_two_instances() {
         do run_in_bare_thread {
             local_ptr::init();
-            let mut sched = ~new_test_uv_sched();
-            let task = ~Task::new_root(&mut sched.stack_pool, None, proc(){});
+            let task = ~Task::new();
             Local::put(task);
             let task: ~Task = Local::take();
             cleanup_task(task);
-            let task = ~Task::new_root(&mut sched.stack_pool, None, proc(){});
+            let task = ~Task::new();
             Local::put(task);
             let task: ~Task = Local::take();
             cleanup_task(task);
@@ -164,8 +84,7 @@ mod test {
     fn borrow_smoke_test() {
         do run_in_bare_thread {
             local_ptr::init();
-            let mut sched = ~new_test_uv_sched();
-            let task = ~Task::new_root(&mut sched.stack_pool, None, proc(){});
+            let task = ~Task::new();
             Local::put(task);
 
             unsafe {
@@ -180,8 +99,7 @@ mod test {
     fn borrow_with_return() {
         do run_in_bare_thread {
             local_ptr::init();
-            let mut sched = ~new_test_uv_sched();
-            let task = ~Task::new_root(&mut sched.stack_pool, None, proc(){});
+            let task = ~Task::new();
             Local::put(task);
 
             {
@@ -193,5 +111,9 @@ mod test {
         }
     }
 
+    fn cleanup_task(mut t: ~Task) {
+        t.destroyed = true;
+    }
+
 }
 
diff --git a/src/libstd/rt/local_ptr.rs b/src/libstd/rt/local_ptr.rs
index 925aa802ad5..42cce272e44 100644
--- a/src/libstd/rt/local_ptr.rs
+++ b/src/libstd/rt/local_ptr.rs
@@ -42,7 +42,7 @@ impl<T> Drop for Borrowed<T> {
             }
             let val: ~T = cast::transmute(self.val);
             put::<T>(val);
-            assert!(exists());
+            rtassert!(exists());
         }
     }
 }
@@ -109,7 +109,9 @@ pub mod compiled {
     /// Does not validate the pointer type.
     #[inline]
     pub unsafe fn take<T>() -> ~T {
-        let ptr: ~T = cast::transmute(RT_TLS_PTR);
+        let ptr = RT_TLS_PTR;
+        rtassert!(!ptr.is_null());
+        let ptr: ~T = cast::transmute(ptr);
         // can't use `as`, due to type not matching with `cfg(test)`
         RT_TLS_PTR = cast::transmute(0);
         ptr
@@ -178,7 +180,7 @@ pub mod native {
     }
 
     pub unsafe fn cleanup() {
-        assert!(INITIALIZED);
+        rtassert!(INITIALIZED);
         tls::destroy(RT_TLS_KEY);
         LOCK.destroy();
         INITIALIZED = false;
diff --git a/src/libstd/rt/mod.rs b/src/libstd/rt/mod.rs
index df1ebeb6407..0dd6c883d5b 100644
--- a/src/libstd/rt/mod.rs
+++ b/src/libstd/rt/mod.rs
@@ -57,27 +57,17 @@ Several modules in `core` are clients of `rt`:
 // XXX: this should not be here.
 #[allow(missing_doc)];
 
+use any::Any;
 use clone::Clone;
 use container::Container;
 use iter::Iterator;
-use option::{Option, None, Some};
+use option::Option;
 use ptr::RawPtr;
-use rt::local::Local;
-use rt::sched::{Scheduler, Shutdown};
-use rt::sleeper_list::SleeperList;
-use task::TaskResult;
-use rt::task::{Task, SchedTask, GreenTask, Sched};
-use send_str::SendStrStatic;
-use unstable::atomics::{AtomicInt, AtomicBool, SeqCst};
-use unstable::sync::UnsafeArc;
+use result::Result;
+use task::TaskOpts;
 use vec::{OwnedVector, MutableVector, ImmutableVector};
-use vec;
 
-use self::thread::Thread;
-
-// the os module needs to reach into this helper, so allow general access
-// through this reexport.
-pub use self::util::set_exit_status;
+use self::task::{Task, BlockedTask};
 
 // this is somewhat useful when a program wants to spawn a "reasonable" number
 // of workers based on the constraints of the system that it's running on.
@@ -85,8 +75,8 @@ pub use self::util::set_exit_status;
 // method...
 pub use self::util::default_sched_threads;
 
-// Re-export of the functionality in the kill module
-pub use self::kill::BlockedTask;
+// Export unwinding facilities used by the failure macros
+pub use self::unwind::{begin_unwind, begin_unwind_raw};
 
 // XXX: these probably shouldn't be public...
 #[doc(hidden)]
@@ -99,21 +89,12 @@ pub mod shouldnt_be_public {
 // Internal macros used by the runtime.
 mod macros;
 
-/// Basic implementation of an EventLoop, provides no I/O interfaces
-mod basic;
-
 /// The global (exchange) heap.
 pub mod global_heap;
 
 /// Implementations of language-critical runtime features like @.
 pub mod task;
 
-/// Facilities related to task failure, killing, and death.
-mod kill;
-
-/// The coroutine task scheduler, built on the `io` event loop.
-pub mod sched;
-
 /// The EventLoop and internal synchronous I/O interface.
 pub mod rtio;
 
@@ -121,27 +102,6 @@ pub mod rtio;
 /// or task-local storage.
 pub mod local;
 
-/// A mostly lock-free multi-producer, single consumer queue.
-pub mod mpsc_queue;
-
-/// A lock-free single-producer, single consumer queue.
-pub mod spsc_queue;
-
-/// A lock-free multi-producer, multi-consumer bounded queue.
-mod mpmc_bounded_queue;
-
-/// A parallel work-stealing deque
-pub mod deque;
-
-/// A parallel data structure for tracking sleeping schedulers.
-pub mod sleeper_list;
-
-/// Stack segments and caching.
-pub mod stack;
-
-/// CPU context swapping.
-mod context;
-
 /// Bindings to system threading libraries.
 pub mod thread;
 
@@ -157,16 +117,6 @@ pub mod logging;
 /// Crate map
 pub mod crate_map;
 
-/// Tools for testing the runtime
-pub mod test;
-
-/// Reference counting
-pub mod rc;
-
-/// A simple single-threaded channel type for passing buffered data between
-/// scheduler and task context
-pub mod tube;
-
 /// The runtime needs to be able to put a pointer into thread-local storage.
 mod local_ptr;
 
@@ -185,41 +135,33 @@ pub mod args;
 // Support for dynamic borrowck
 pub mod borrowck;
 
-/// Set up a default runtime configuration, given compiler-supplied arguments.
-///
-/// This is invoked by the `start` _language item_ (unstable::lang) to
-/// run a Rust executable.
-///
-/// # Arguments
-///
-/// * `argc` & `argv` - The argument vector. On Unix this information is used
-///   by os::args.
-///
-/// # Return value
-///
-/// The return value is used as the process return code. 0 on success, 101 on error.
-pub fn start(argc: int, argv: **u8, main: proc()) -> int {
-
-    init(argc, argv);
-    let exit_code = run(main);
-    // unsafe is ok b/c we're sure that the runtime is gone
-    unsafe { cleanup(); }
-
-    return exit_code;
-}
+/// The default error code of the rust runtime if the main task fails instead
+/// of exiting cleanly.
+pub static DEFAULT_ERROR_CODE: int = 101;
 
-/// Like `start` but creates an additional scheduler on the current thread,
-/// which in most cases will be the 'main' thread, and pins the main task to it.
+/// The interface to the current runtime.
 ///
-/// This is appropriate for running code that must execute on the main thread,
-/// such as the platform event loop and GUI.
-pub fn start_on_main_thread(argc: int, argv: **u8, main: proc()) -> int {
-    init(argc, argv);
-    let exit_code = run_on_main_thread(main);
-    // unsafe is ok b/c we're sure that the runtime is gone
-    unsafe { cleanup(); }
-
-    return exit_code;
+/// This trait is used as the abstraction between 1:1 and M:N scheduling. The
+/// two independent crates, libnative and libgreen, both have objects which
+/// implement this trait. The goal of this trait is to encompass all the
+/// fundamental differences in functionality between the 1:1 and M:N runtime
+/// modes.
+pub trait Runtime {
+    // Necessary scheduling functions, used for channels and blocking I/O
+    // (sometimes).
+    fn yield_now(~self, cur_task: ~Task);
+    fn maybe_yield(~self, cur_task: ~Task);
+    fn deschedule(~self, times: uint, cur_task: ~Task,
+                  f: |BlockedTask| -> Result<(), BlockedTask>);
+    fn reawaken(~self, to_wake: ~Task, can_resched: bool);
+
+    // Miscellaneous calls which are very different depending on what context
+    // you're in.
+    fn spawn_sibling(~self, cur_task: ~Task, opts: TaskOpts, f: proc());
+    fn local_io<'a>(&'a mut self) -> Option<rtio::LocalIo<'a>>;
+
+    // XXX: This is a serious code smell and this should not exist at all.
+    fn wrap(~self) -> ~Any;
 }
 
 /// One-time runtime initialization.
@@ -234,6 +176,7 @@ pub fn init(argc: int, argv: **u8) {
         args::init(argc, argv);
         env::init();
         logging::init();
+        local_ptr::init();
     }
 }
 
@@ -250,239 +193,3 @@ pub unsafe fn cleanup() {
     args::cleanup();
     local_ptr::cleanup();
 }
-
-/// Execute the main function in a scheduler.
-///
-/// Configures the runtime according to the environment, by default
-/// using a task scheduler with the same number of threads as cores.
-/// Returns a process exit code.
-pub fn run(main: proc()) -> int {
-    run_(main, false)
-}
-
-pub fn run_on_main_thread(main: proc()) -> int {
-    run_(main, true)
-}
-
-fn run_(main: proc(), use_main_sched: bool) -> int {
-    static DEFAULT_ERROR_CODE: int = 101;
-
-    let nscheds = util::default_sched_threads();
-
-    let mut main = Some(main);
-
-    // The shared list of sleeping schedulers.
-    let sleepers = SleeperList::new();
-
-    // Create a work queue for each scheduler, ntimes. Create an extra
-    // for the main thread if that flag is set. We won't steal from it.
-    let mut pool = deque::BufferPool::new();
-    let arr = vec::from_fn(nscheds, |_| pool.deque());
-    let (workers, stealers) = vec::unzip(arr.move_iter());
-
-    // The schedulers.
-    let mut scheds = ~[];
-    // Handles to the schedulers. When the main task ends these will be
-    // sent the Shutdown message to terminate the schedulers.
-    let mut handles = ~[];
-
-    for worker in workers.move_iter() {
-        rtdebug!("inserting a regular scheduler");
-
-        // Every scheduler is driven by an I/O event loop.
-        let loop_ = new_event_loop();
-        let mut sched = ~Scheduler::new(loop_,
-                                        worker,
-                                        stealers.clone(),
-                                        sleepers.clone());
-        let handle = sched.make_handle();
-
-        scheds.push(sched);
-        handles.push(handle);
-    }
-
-    // If we need a main-thread task then create a main thread scheduler
-    // that will reject any task that isn't pinned to it
-    let main_sched = if use_main_sched {
-
-        // Create a friend handle.
-        let mut friend_sched = scheds.pop();
-        let friend_handle = friend_sched.make_handle();
-        scheds.push(friend_sched);
-
-        // This scheduler needs a queue that isn't part of the stealee
-        // set.
-        let (worker, _) = pool.deque();
-
-        let main_loop = new_event_loop();
-        let mut main_sched = ~Scheduler::new_special(main_loop,
-                                                     worker,
-                                                     stealers.clone(),
-                                                     sleepers.clone(),
-                                                     false,
-                                                     Some(friend_handle));
-        let mut main_handle = main_sched.make_handle();
-        // Allow the scheduler to exit when the main task exits.
-        // Note: sending the shutdown message also prevents the scheduler
-        // from pushing itself to the sleeper list, which is used for
-        // waking up schedulers for work stealing; since this is a
-        // non-work-stealing scheduler it should not be adding itself
-        // to the list.
-        main_handle.send(Shutdown);
-        Some(main_sched)
-    } else {
-        None
-    };
-
-    // Create a shared cell for transmitting the process exit
-    // code from the main task to this function.
-    let exit_code = UnsafeArc::new(AtomicInt::new(0));
-    let exit_code_clone = exit_code.clone();
-
-    // Used to sanity check that the runtime only exits once
-    let exited_already = UnsafeArc::new(AtomicBool::new(false));
-
-    // When the main task exits, after all the tasks in the main
-    // task tree, shut down the schedulers and set the exit code.
-    let handles = handles;
-    let on_exit: proc(TaskResult) = proc(exit_success) {
-        unsafe {
-            assert!(!(*exited_already.get()).swap(true, SeqCst),
-                    "the runtime already exited");
-        }
-
-        let mut handles = handles;
-        for handle in handles.mut_iter() {
-            handle.send(Shutdown);
-        }
-
-        unsafe {
-            let exit_code = if exit_success.is_ok() {
-                use rt::util;
-
-                // If we're exiting successfully, then return the global
-                // exit status, which can be set programmatically.
-                util::get_exit_status()
-            } else {
-                DEFAULT_ERROR_CODE
-            };
-            (*exit_code_clone.get()).store(exit_code, SeqCst);
-        }
-    };
-
-    let mut threads = ~[];
-    let mut on_exit = Some(on_exit);
-
-    if !use_main_sched {
-
-        // In the case where we do not use a main_thread scheduler we
-        // run the main task in one of our threads.
-
-        let mut main_task = ~Task::new_root(&mut scheds[0].stack_pool,
-                                            None,
-                                            ::util::replace(&mut main,
-                                                            None).unwrap());
-        main_task.name = Some(SendStrStatic("<main>"));
-        main_task.death.on_exit = ::util::replace(&mut on_exit, None);
-
-        let sched = scheds.pop();
-        let main_task = main_task;
-        let thread = do Thread::start {
-            sched.bootstrap(main_task);
-        };
-        threads.push(thread);
-    }
-
-    // Run each remaining scheduler in a thread.
-    for sched in scheds.move_rev_iter() {
-        rtdebug!("creating regular schedulers");
-        let thread = do Thread::start {
-            let mut sched = sched;
-            let bootstrap_task = ~do Task::new_root(&mut sched.stack_pool, None) || {
-                rtdebug!("boostraping a non-primary scheduler");
-            };
-            sched.bootstrap(bootstrap_task);
-        };
-        threads.push(thread);
-    }
-
-    // If we do have a main thread scheduler, run it now.
-
-    if use_main_sched {
-        rtdebug!("about to create the main scheduler task");
-
-        let mut main_sched = main_sched.unwrap();
-
-        let home = Sched(main_sched.make_handle());
-        let mut main_task = ~Task::new_root_homed(&mut main_sched.stack_pool,
-                                                  None,
-                                                  home,
-                                                  ::util::replace(&mut main,
-                                                                  None).
-                                                                  unwrap());
-        main_task.name = Some(SendStrStatic("<main>"));
-        main_task.death.on_exit = ::util::replace(&mut on_exit, None);
-        rtdebug!("bootstrapping main_task");
-
-        main_sched.bootstrap(main_task);
-    }
-
-    rtdebug!("waiting for threads");
-
-    // Wait for schedulers
-    for thread in threads.move_iter() {
-        thread.join();
-    }
-
-    // Return the exit code
-    unsafe {
-        (*exit_code.get()).load(SeqCst)
-    }
-}
-
-pub fn in_sched_context() -> bool {
-    unsafe {
-        let task_ptr: Option<*mut Task> = Local::try_unsafe_borrow();
-        match task_ptr {
-            Some(task) => {
-                match (*task).task_type {
-                    SchedTask => true,
-                    _ => false
-                }
-            }
-            None => false
-        }
-    }
-}
-
-pub fn in_green_task_context() -> bool {
-    unsafe {
-        let task: Option<*mut Task> = Local::try_unsafe_borrow();
-        match task {
-            Some(task) => {
-                match (*task).task_type {
-                    GreenTask(_) => true,
-                    _ => false
-                }
-            }
-            None => false
-        }
-    }
-}
-
-pub fn new_event_loop() -> ~rtio::EventLoop {
-    match crate_map::get_crate_map() {
-        None => {}
-        Some(map) => {
-            match map.event_loop_factory {
-                None => {}
-                Some(factory) => return factory()
-            }
-        }
-    }
-
-    // If the crate map didn't specify a factory to create an event loop, then
-    // instead just use a basic event loop missing all I/O services to at least
-    // get the scheduler running.
-    return basic::event_loop();
-}
diff --git a/src/libstd/rt/mpmc_bounded_queue.rs b/src/libstd/rt/mpmc_bounded_queue.rs
deleted file mode 100644
index 25a3ba8ab48..00000000000
--- a/src/libstd/rt/mpmc_bounded_queue.rs
+++ /dev/null
@@ -1,209 +0,0 @@
-/* Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- *    1. Redistributions of source code must retain the above copyright notice,
- *       this list of conditions and the following disclaimer.
- *
- *    2. Redistributions in binary form must reproduce the above copyright
- *       notice, this list of conditions and the following disclaimer in the
- *       documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
- * SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
- * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * The views and conclusions contained in the software and documentation are
- * those of the authors and should not be interpreted as representing official
- * policies, either expressed or implied, of Dmitry Vyukov.
- */
-
-// http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue
-
-use unstable::sync::UnsafeArc;
-use unstable::atomics::{AtomicUint,Relaxed,Release,Acquire};
-use option::*;
-use vec;
-use clone::Clone;
-use kinds::Send;
-use num::{Exponential,Algebraic,Round};
-
-struct Node<T> {
-    sequence: AtomicUint,
-    value: Option<T>,
-}
-
-struct State<T> {
-    pad0: [u8, ..64],
-    buffer: ~[Node<T>],
-    mask: uint,
-    pad1: [u8, ..64],
-    enqueue_pos: AtomicUint,
-    pad2: [u8, ..64],
-    dequeue_pos: AtomicUint,
-    pad3: [u8, ..64],
-}
-
-pub struct Queue<T> {
-    priv state: UnsafeArc<State<T>>,
-}
-
-impl<T: Send> State<T> {
-    fn with_capacity(capacity: uint) -> State<T> {
-        let capacity = if capacity < 2 || (capacity & (capacity - 1)) != 0 {
-            if capacity < 2 {
-                2u
-            } else {
-                // use next power of 2 as capacity
-                2f64.pow(&((capacity as f64).log2().ceil())) as uint
-            }
-        } else {
-            capacity
-        };
-        let buffer = vec::from_fn(capacity, |i:uint| {
-            Node{sequence:AtomicUint::new(i),value:None}
-        });
-        State{
-            pad0: [0, ..64],
-            buffer: buffer,
-            mask: capacity-1,
-            pad1: [0, ..64],
-            enqueue_pos: AtomicUint::new(0),
-            pad2: [0, ..64],
-            dequeue_pos: AtomicUint::new(0),
-            pad3: [0, ..64],
-        }
-    }
-
-    fn push(&mut self, value: T) -> bool {
-        let mask = self.mask;
-        let mut pos = self.enqueue_pos.load(Relaxed);
-        loop {
-            let node = &mut self.buffer[pos & mask];
-            let seq = node.sequence.load(Acquire);
-            let diff: int = seq as int - pos as int;
-
-            if diff == 0 {
-                let enqueue_pos = self.enqueue_pos.compare_and_swap(pos, pos+1, Relaxed);
-                if enqueue_pos == pos {
-                    node.value = Some(value);
-                    node.sequence.store(pos+1, Release);
-                    break
-                } else {
-                    pos = enqueue_pos;
-                }
-            } else if (diff < 0) {
-                return false
-            } else {
-                pos = self.enqueue_pos.load(Relaxed);
-            }
-        }
-        true
-    }
-
-    fn pop(&mut self) -> Option<T> {
-        let mask = self.mask;
-        let mut pos = self.dequeue_pos.load(Relaxed);
-        loop {
-            let node = &mut self.buffer[pos & mask];
-            let seq = node.sequence.load(Acquire);
-            let diff: int = seq as int - (pos + 1) as int;
-            if diff == 0 {
-                let dequeue_pos = self.dequeue_pos.compare_and_swap(pos, pos+1, Relaxed);
-                if dequeue_pos == pos {
-                    let value = node.value.take();
-                    node.sequence.store(pos + mask + 1, Release);
-                    return value
-                } else {
-                    pos = dequeue_pos;
-                }
-            } else if diff < 0 {
-                return None
-            } else {
-                pos = self.dequeue_pos.load(Relaxed);
-            }
-        }
-    }
-}
-
-impl<T: Send> Queue<T> {
-    pub fn with_capacity(capacity: uint) -> Queue<T> {
-        Queue{
-            state: UnsafeArc::new(State::with_capacity(capacity))
-        }
-    }
-
-    pub fn push(&mut self, value: T) -> bool {
-        unsafe { (*self.state.get()).push(value) }
-    }
-
-    pub fn pop(&mut self) -> Option<T> {
-        unsafe { (*self.state.get()).pop() }
-    }
-}
-
-impl<T: Send> Clone for Queue<T> {
-    fn clone(&self) -> Queue<T> {
-        Queue {
-            state: self.state.clone()
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use prelude::*;
-    use option::*;
-    use task;
-    use super::Queue;
-
-    #[test]
-    fn test() {
-        let nthreads = 8u;
-        let nmsgs = 1000u;
-        let mut q = Queue::with_capacity(nthreads*nmsgs);
-        assert_eq!(None, q.pop());
-
-        for _ in range(0, nthreads) {
-            let q = q.clone();
-            do task::spawn_sched(task::SingleThreaded) {
-                let mut q = q;
-                for i in range(0, nmsgs) {
-                    assert!(q.push(i));
-                }
-            }
-        }
-
-        let mut completion_ports = ~[];
-        for _ in range(0, nthreads) {
-            let (completion_port, completion_chan) = Chan::new();
-            completion_ports.push(completion_port);
-            let q = q.clone();
-            do task::spawn_sched(task::SingleThreaded) {
-                let mut q = q;
-                let mut i = 0u;
-                loop {
-                    match q.pop() {
-                        None => {},
-                        Some(_) => {
-                            i += 1;
-                            if i == nmsgs { break }
-                        }
-                    }
-                }
-                completion_chan.send(i);
-            }
-        }
-
-        for completion_port in completion_ports.mut_iter() {
-            assert_eq!(nmsgs, completion_port.recv());
-        }
-    }
-}
diff --git a/src/libstd/rt/mpsc_queue.rs b/src/libstd/rt/mpsc_queue.rs
deleted file mode 100644
index d575028af70..00000000000
--- a/src/libstd/rt/mpsc_queue.rs
+++ /dev/null
@@ -1,215 +0,0 @@
-/* Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- *    1. Redistributions of source code must retain the above copyright notice,
- *       this list of conditions and the following disclaimer.
- *
- *    2. Redistributions in binary form must reproduce the above copyright
- *       notice, this list of conditions and the following disclaimer in the
- *       documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
- * SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
- * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * The views and conclusions contained in the software and documentation are
- * those of the authors and should not be interpreted as representing official
- * policies, either expressed or implied, of Dmitry Vyukov.
- */
-
-//! A mostly lock-free multi-producer, single consumer queue.
-
-// http://www.1024cores.net/home/lock-free-algorithms
-//                         /queues/non-intrusive-mpsc-node-based-queue
-
-use cast;
-use clone::Clone;
-use kinds::Send;
-use ops::Drop;
-use option::{Option, None, Some};
-use unstable::atomics::{AtomicPtr, Release, Acquire, AcqRel, Relaxed};
-use unstable::sync::UnsafeArc;
-
-pub enum PopResult<T> {
-    /// Some data has been popped
-    Data(T),
-    /// The queue is empty
-    Empty,
-    /// The queue is in an inconsistent state. Popping data should succeed, but
-    /// some pushers have yet to make enough progress in order allow a pop to
-    /// succeed. It is recommended that a pop() occur "in the near future" in
-    /// order to see if the sender has made progress or not
-    Inconsistent,
-}
-
-struct Node<T> {
-    next: AtomicPtr<Node<T>>,
-    value: Option<T>,
-}
-
-struct State<T, P> {
-    head: AtomicPtr<Node<T>>,
-    tail: *mut Node<T>,
-    packet: P,
-}
-
-pub struct Consumer<T, P> {
-    priv state: UnsafeArc<State<T, P>>,
-}
-
-pub struct Producer<T, P> {
-    priv state: UnsafeArc<State<T, P>>,
-}
-
-impl<T: Send, P: Send> Clone for Producer<T, P> {
-    fn clone(&self) -> Producer<T, P> {
-        Producer { state: self.state.clone() }
-    }
-}
-
-pub fn queue<T: Send, P: Send>(p: P) -> (Consumer<T, P>, Producer<T, P>) {
-    unsafe {
-        let (a, b) = UnsafeArc::new2(State::new(p));
-        (Consumer { state: a }, Producer { state: b })
-    }
-}
-
-impl<T> Node<T> {
-    unsafe fn new(v: Option<T>) -> *mut Node<T> {
-        cast::transmute(~Node {
-            next: AtomicPtr::new(0 as *mut Node<T>),
-            value: v,
-        })
-    }
-}
-
-impl<T: Send, P: Send> State<T, P> {
-    pub unsafe fn new(p: P) -> State<T, P> {
-        let stub = Node::new(None);
-        State {
-            head: AtomicPtr::new(stub),
-            tail: stub,
-            packet: p,
-        }
-    }
-
-    unsafe fn push(&mut self, t: T) {
-        let n = Node::new(Some(t));
-        let prev = self.head.swap(n, AcqRel);
-        (*prev).next.store(n, Release);
-    }
-
-    unsafe fn pop(&mut self) -> PopResult<T> {
-        let tail = self.tail;
-        let next = (*tail).next.load(Acquire);
-
-        if !next.is_null() {
-            self.tail = next;
-            assert!((*tail).value.is_none());
-            assert!((*next).value.is_some());
-            let ret = (*next).value.take_unwrap();
-            let _: ~Node<T> = cast::transmute(tail);
-            return Data(ret);
-        }
-
-        if self.head.load(Acquire) == tail {Empty} else {Inconsistent}
-    }
-
-    unsafe fn is_empty(&mut self) -> bool {
-        return (*self.tail).next.load(Acquire).is_null();
-    }
-}
-
-#[unsafe_destructor]
-impl<T: Send, P: Send> Drop for State<T, P> {
-    fn drop(&mut self) {
-        unsafe {
-            let mut cur = self.tail;
-            while !cur.is_null() {
-                let next = (*cur).next.load(Relaxed);
-                let _: ~Node<T> = cast::transmute(cur);
-                cur = next;
-            }
-        }
-    }
-}
-
-impl<T: Send, P: Send> Producer<T, P> {
-    pub fn push(&mut self, value: T) {
-        unsafe { (*self.state.get()).push(value) }
-    }
-    pub fn is_empty(&self) -> bool {
-        unsafe{ (*self.state.get()).is_empty() }
-    }
-    pub unsafe fn packet(&self) -> *mut P {
-        &mut (*self.state.get()).packet as *mut P
-    }
-}
-
-impl<T: Send, P: Send> Consumer<T, P> {
-    pub fn pop(&mut self) -> PopResult<T> {
-        unsafe { (*self.state.get()).pop() }
-    }
-    pub fn casual_pop(&mut self) -> Option<T> {
-        match self.pop() {
-            Data(t) => Some(t),
-            Empty | Inconsistent => None,
-        }
-    }
-    pub unsafe fn packet(&self) -> *mut P {
-        &mut (*self.state.get()).packet as *mut P
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use prelude::*;
-
-    use task;
-    use super::{queue, Data, Empty, Inconsistent};
-
-    #[test]
-    fn test_full() {
-        let (_, mut p) = queue(());
-        p.push(~1);
-        p.push(~2);
-    }
-
-    #[test]
-    fn test() {
-        let nthreads = 8u;
-        let nmsgs = 1000u;
-        let (mut c, p) = queue(());
-        match c.pop() {
-            Empty => {}
-            Inconsistent | Data(..) => fail!()
-        }
-
-        for _ in range(0, nthreads) {
-            let q = p.clone();
-            do task::spawn_sched(task::SingleThreaded) {
-                let mut q = q;
-                for i in range(0, nmsgs) {
-                    q.push(i);
-                }
-            }
-        }
-
-        let mut i = 0u;
-        while i < nthreads * nmsgs {
-            match c.pop() {
-                Empty | Inconsistent => {},
-                Data(_) => { i += 1 }
-            }
-        }
-    }
-}
-
diff --git a/src/libstd/rt/rc.rs b/src/libstd/rt/rc.rs
deleted file mode 100644
index 2699dab6d38..00000000000
--- a/src/libstd/rt/rc.rs
+++ /dev/null
@@ -1,139 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! An owned, task-local, reference counted type
-//!
-//! # Safety note
-//!
-//! XXX There is currently no type-system mechanism for enforcing that
-//! reference counted types are both allocated on the exchange heap
-//! and also non-sendable
-//!
-//! This doesn't prevent borrowing multiple aliasable mutable pointers
-
-use ops::Drop;
-use clone::Clone;
-use libc::c_void;
-use cast;
-
-pub struct RC<T> {
-    priv p: *c_void // ~(uint, T)
-}
-
-impl<T> RC<T> {
-    pub fn new(val: T) -> RC<T> {
-        unsafe {
-            let v = ~(1, val);
-            let p: *c_void = cast::transmute(v);
-            RC { p: p }
-        }
-    }
-
-    fn get_mut_state(&mut self) -> *mut (uint, T) {
-        unsafe {
-            let p: &mut ~(uint, T) = cast::transmute(&mut self.p);
-            let p: *mut (uint, T) = &mut **p;
-            return p;
-        }
-    }
-
-    fn get_state(&self) -> *(uint, T) {
-        unsafe {
-            let p: &~(uint, T) = cast::transmute(&self.p);
-            let p: *(uint, T) = &**p;
-            return p;
-        }
-    }
-
-    pub fn unsafe_borrow_mut(&mut self) -> *mut T {
-        unsafe {
-            match *self.get_mut_state() {
-                (_, ref mut p) => {
-                    let p: *mut T = p;
-                    return p;
-                }
-            }
-        }
-    }
-
-    pub fn refcount(&self) -> uint {
-        unsafe {
-            match *self.get_state() {
-                (count, _) => count
-            }
-        }
-    }
-}
-
-#[unsafe_destructor]
-impl<T> Drop for RC<T> {
-    fn drop(&mut self) {
-        assert!(self.refcount() > 0);
-
-        unsafe {
-            match *self.get_mut_state() {
-                (ref mut count, _) => {
-                    *count = *count - 1
-                }
-            }
-
-            if self.refcount() == 0 {
-                let _: ~(uint, T) = cast::transmute(self.p);
-            }
-        }
-    }
-}
-
-impl<T> Clone for RC<T> {
-    fn clone(&self) -> RC<T> {
-        unsafe {
-            // XXX: Mutable clone
-            let this: &mut RC<T> = cast::transmute_mut(self);
-
-            match *this.get_mut_state() {
-                (ref mut count, _) => {
-                    *count = *count + 1;
-                }
-            }
-        }
-
-        RC { p: self.p }
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::RC;
-
-    #[test]
-    fn smoke_test() {
-        unsafe {
-            let mut v1 = RC::new(100);
-            assert!(*v1.unsafe_borrow_mut() == 100);
-            assert!(v1.refcount() == 1);
-
-            let mut v2 = v1.clone();
-            assert!(*v2.unsafe_borrow_mut() == 100);
-            assert!(v2.refcount() == 2);
-
-            *v2.unsafe_borrow_mut() = 200;
-            assert!(*v2.unsafe_borrow_mut() == 200);
-            assert!(*v1.unsafe_borrow_mut() == 200);
-
-            let v3 = v2.clone();
-            assert!(v3.refcount() == 3);
-            {
-                let _v1 = v1;
-                let _v2 = v2;
-            }
-            assert!(v3.refcount() == 1);
-        }
-    }
-}
diff --git a/src/libstd/rt/rtio.rs b/src/libstd/rt/rtio.rs
index b54231421e3..6b3d50a76ac 100644
--- a/src/libstd/rt/rtio.rs
+++ b/src/libstd/rt/rtio.rs
@@ -14,14 +14,15 @@ use comm::{SharedChan, Port};
 use libc::c_int;
 use libc;
 use ops::Drop;
-use option::*;
+use option::{Option, Some, None};
 use path::Path;
-use result::*;
+use result::{Result, Ok, Err};
+use rt::task::Task;
+use rt::local::Local;
 
 use ai = io::net::addrinfo;
+use io;
 use io::IoError;
-use io::native::NATIVE_IO_FACTORY;
-use io::native;
 use io::net::ip::{IpAddr, SocketAddr};
 use io::process::{ProcessConfig, ProcessExit};
 use io::signal::Signum;
@@ -93,36 +94,52 @@ impl<'a> Drop for LocalIo<'a> {
 impl<'a> LocalIo<'a> {
     /// Returns the local I/O: either the local scheduler's I/O services or
     /// the native I/O services.
-    pub fn borrow() -> LocalIo {
-        use rt::sched::Scheduler;
-        use rt::local::Local;
+    pub fn borrow() -> Option<LocalIo> {
+        // FIXME(#11053): bad
+        //
+        // This is currently very unsafely implemented. We don't actually
+        // *take* the local I/O so there's a very real possibility that we
+        // can have two borrows at once. Currently there is not a clear way
+        // to actually borrow the local I/O factory safely because even if
+        // ownership were transferred down to the functions that the I/O
+        // factory implements it's just too much of a pain to know when to
+        // relinquish ownership back into the local task (but that would be
+        // the safe way of implementing this function).
+        //
+        // In order to get around this, we just transmute a copy out of the task
+        // in order to have what is likely a static lifetime (bad).
+        let mut t: ~Task = Local::take();
+        let ret = t.local_io().map(|t| {
+            unsafe { cast::transmute_copy(&t) }
+        });
+        Local::put(t);
+        return ret;
+    }
 
-        unsafe {
-            // First, attempt to use the local scheduler's I/O services
-            let sched: Option<*mut Scheduler> = Local::try_unsafe_borrow();
-            match sched {
-                Some(sched) => {
-                    match (*sched).event_loop.io() {
-                        Some(factory) => {
-                            return LocalIo {
-                                factory: factory,
-                            }
-                        }
-                        None => {}
+    pub fn maybe_raise<T>(f: |io: &mut IoFactory| -> Result<T, IoError>)
+        -> Option<T>
+    {
+        match LocalIo::borrow() {
+            None => {
+                io::io_error::cond.raise(io::standard_error(io::IoUnavailable));
+                None
+            }
+            Some(mut io) => {
+                match f(io.get()) {
+                    Ok(t) => Some(t),
+                    Err(ioerr) => {
+                        io::io_error::cond.raise(ioerr);
+                        None
                     }
                 }
-                None => {}
-            }
-            // If we don't have a scheduler or the scheduler doesn't have I/O
-            // services, then fall back to the native I/O services.
-            let native_io: &'static mut native::IoFactory =
-                &mut NATIVE_IO_FACTORY;
-            LocalIo {
-                factory: native_io as &mut IoFactory:'static
             }
         }
     }
 
+    pub fn new<'a>(io: &'a mut IoFactory) -> LocalIo<'a> {
+        LocalIo { factory: io }
+    }
+
     /// Returns the underlying I/O factory as a trait reference.
     #[inline]
     pub fn get<'a>(&'a mut self) -> &'a mut IoFactory {
diff --git a/src/libstd/rt/sched.rs b/src/libstd/rt/sched.rs
deleted file mode 100644
index 15aa1602cd0..00000000000
--- a/src/libstd/rt/sched.rs
+++ /dev/null
@@ -1,1395 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-use option::{Option, Some, None};
-use cast::{transmute, transmute_mut_region, transmute_mut_unsafe};
-use clone::Clone;
-use unstable::raw;
-use super::sleeper_list::SleeperList;
-use super::stack::{StackPool};
-use super::rtio::EventLoop;
-use super::context::Context;
-use super::task::{Task, AnySched, Sched};
-use rt::kill::BlockedTask;
-use rt::deque;
-use rt::local_ptr;
-use rt::local::Local;
-use rt::rtio::{RemoteCallback, PausableIdleCallback, Callback};
-use borrow::{to_uint};
-use rand::{XorShiftRng, Rng, Rand};
-use iter::range;
-use unstable::mutex::Mutex;
-use vec::{OwnedVector};
-
-use mpsc = super::mpsc_queue;
-
-/// A scheduler is responsible for coordinating the execution of Tasks
-/// on a single thread. The scheduler runs inside a slightly modified
-/// Rust Task. When not running this task is stored in the scheduler
-/// struct. The scheduler struct acts like a baton, all scheduling
-/// actions are transfers of the baton.
-///
-/// XXX: This creates too many callbacks to run_sched_once, resulting
-/// in too much allocation and too many events.
-pub struct Scheduler {
-    /// There are N work queues, one per scheduler.
-    work_queue: deque::Worker<~Task>,
-    /// Work queues for the other schedulers. These are created by
-    /// cloning the core work queues.
-    work_queues: ~[deque::Stealer<~Task>],
-    /// The queue of incoming messages from other schedulers.
-    /// These are enqueued by SchedHandles after which a remote callback
-    /// is triggered to handle the message.
-    message_queue: mpsc::Consumer<SchedMessage, ()>,
-    /// Producer used to clone sched handles from
-    message_producer: mpsc::Producer<SchedMessage, ()>,
-    /// A shared list of sleeping schedulers. We'll use this to wake
-    /// up schedulers when pushing work onto the work queue.
-    sleeper_list: SleeperList,
-    /// Indicates that we have previously pushed a handle onto the
-    /// SleeperList but have not yet received the Wake message.
-    /// Being `true` does not necessarily mean that the scheduler is
-    /// not active since there are multiple event sources that may
-    /// wake the scheduler. It just prevents the scheduler from pushing
-    /// multiple handles onto the sleeper list.
-    sleepy: bool,
-    /// A flag to indicate we've received the shutdown message and should
-    /// no longer try to go to sleep, but exit instead.
-    no_sleep: bool,
-    stack_pool: StackPool,
-    /// The scheduler runs on a special task. When it is not running
-    /// it is stored here instead of the work queue.
-    sched_task: Option<~Task>,
-    /// An action performed after a context switch on behalf of the
-    /// code running before the context switch
-    cleanup_job: Option<CleanupJob>,
-    /// Should this scheduler run any task, or only pinned tasks?
-    run_anything: bool,
-    /// If the scheduler shouldn't run some tasks, a friend to send
-    /// them to.
-    friend_handle: Option<SchedHandle>,
-    /// A fast XorShift rng for scheduler use
-    rng: XorShiftRng,
-    /// A togglable idle callback
-    idle_callback: Option<~PausableIdleCallback>,
-    /// A countdown that starts at a random value and is decremented
-    /// every time a yield check is performed. When it hits 0 a task
-    /// will yield.
-    yield_check_count: uint,
-    /// A flag to tell the scheduler loop it needs to do some stealing
-    /// in order to introduce randomness as part of a yield
-    steal_for_yield: bool,
-
-    // n.b. currently destructors of an object are run in top-to-bottom in order
-    //      of field declaration. Due to its nature, the pausable idle callback
-    //      must have some sort of handle to the event loop, so it needs to get
-    //      destroyed before the event loop itself. For this reason, we destroy
-    //      the event loop last to ensure that any unsafe references to it are
-    //      destroyed before it's actually destroyed.
-
-    /// The event loop used to drive the scheduler and perform I/O
-    event_loop: ~EventLoop,
-}
-
-/// An indication of how hard to work on a given operation, the difference
-/// mainly being whether memory is synchronized or not
-#[deriving(Eq)]
-enum EffortLevel {
-    DontTryTooHard,
-    GiveItYourBest
-}
-
-static MAX_YIELD_CHECKS: uint = 20000;
-
-fn reset_yield_check(rng: &mut XorShiftRng) -> uint {
-    let r: uint = Rand::rand(rng);
-    r % MAX_YIELD_CHECKS + 1
-}
-
-impl Scheduler {
-
-    // * Initialization Functions
-
-    pub fn new(event_loop: ~EventLoop,
-               work_queue: deque::Worker<~Task>,
-               work_queues: ~[deque::Stealer<~Task>],
-               sleeper_list: SleeperList)
-        -> Scheduler {
-
-        Scheduler::new_special(event_loop, work_queue,
-                               work_queues,
-                               sleeper_list, true, None)
-
-    }
-
-    pub fn new_special(event_loop: ~EventLoop,
-                       work_queue: deque::Worker<~Task>,
-                       work_queues: ~[deque::Stealer<~Task>],
-                       sleeper_list: SleeperList,
-                       run_anything: bool,
-                       friend: Option<SchedHandle>)
-        -> Scheduler {
-
-        let (consumer, producer) = mpsc::queue(());
-        let mut sched = Scheduler {
-            sleeper_list: sleeper_list,
-            message_queue: consumer,
-            message_producer: producer,
-            sleepy: false,
-            no_sleep: false,
-            event_loop: event_loop,
-            work_queue: work_queue,
-            work_queues: work_queues,
-            stack_pool: StackPool::new(),
-            sched_task: None,
-            cleanup_job: None,
-            run_anything: run_anything,
-            friend_handle: friend,
-            rng: new_sched_rng(),
-            idle_callback: None,
-            yield_check_count: 0,
-            steal_for_yield: false
-        };
-
-        sched.yield_check_count = reset_yield_check(&mut sched.rng);
-
-        return sched;
-    }
-
-    // XXX: This may eventually need to be refactored so that
-    // the scheduler itself doesn't have to call event_loop.run.
-    // That will be important for embedding the runtime into external
-    // event loops.
-
-    // Take a main task to run, and a scheduler to run it in. Create a
-    // scheduler task and bootstrap into it.
-    pub fn bootstrap(mut ~self, task: ~Task) {
-
-        // Build an Idle callback.
-        let cb = ~SchedRunner as ~Callback;
-        self.idle_callback = Some(self.event_loop.pausable_idle_callback(cb));
-
-        // Initialize the TLS key.
-        local_ptr::init();
-
-        // Create a task for the scheduler with an empty context.
-        let sched_task = ~Task::new_sched_task();
-
-        // Now that we have an empty task struct for the scheduler
-        // task, put it in TLS.
-        Local::put(sched_task);
-
-        // Before starting our first task, make sure the idle callback
-        // is active. As we do not start in the sleep state this is
-        // important.
-        self.idle_callback.get_mut_ref().resume();
-
-        // Now, as far as all the scheduler state is concerned, we are
-        // inside the "scheduler" context. So we can act like the
-        // scheduler and resume the provided task.
-        self.resume_task_immediately(task);
-
-        // Now we are back in the scheduler context, having
-        // successfully run the input task. Start by running the
-        // scheduler. Grab it out of TLS - performing the scheduler
-        // action will have given it away.
-        let sched: ~Scheduler = Local::take();
-
-        rtdebug!("starting scheduler {}", sched.sched_id());
-        sched.run();
-
-        // Close the idle callback.
-        let mut sched: ~Scheduler = Local::take();
-        sched.idle_callback.take();
-        // Make one go through the loop to run the close callback.
-        sched.run();
-
-        // Now that we are done with the scheduler, clean up the
-        // scheduler task. Do so by removing it from TLS and manually
-        // cleaning up the memory it uses. As we didn't actually call
-        // task.run() on the scheduler task we never get through all
-        // the cleanup code it runs.
-        let mut stask: ~Task = Local::take();
-
-        rtdebug!("stopping scheduler {}", stask.sched.get_ref().sched_id());
-
-        // Should not have any messages
-        let message = stask.sched.get_mut_ref().message_queue.pop();
-        rtassert!(match message { mpsc::Empty => true, _ => false });
-
-        stask.destroyed = true;
-    }
-
-    // This does not return a scheduler, as the scheduler is placed
-    // inside the task.
-    pub fn run(mut ~self) {
-
-        // This is unsafe because we need to place the scheduler, with
-        // the event_loop inside, inside our task. But we still need a
-        // mutable reference to the event_loop to give it the "run"
-        // command.
-        unsafe {
-            let event_loop: *mut ~EventLoop = &mut self.event_loop;
-
-            {
-                // Our scheduler must be in the task before the event loop
-                // is started.
-                let mut stask = Local::borrow(None::<Task>);
-                stask.get().sched = Some(self);
-            }
-
-            (*event_loop).run();
-        }
-    }
-
-    // * Execution Functions - Core Loop Logic
-
-    // The model for this function is that you continue through it
-    // until you either use the scheduler while performing a schedule
-    // action, in which case you give it away and return early, or
-    // you reach the end and sleep. In the case that a scheduler
-    // action is performed the loop is evented such that this function
-    // is called again.
-    fn run_sched_once() {
-
-        // When we reach the scheduler context via the event loop we
-        // already have a scheduler stored in our local task, so we
-        // start off by taking it. This is the only path through the
-        // scheduler where we get the scheduler this way.
-        let mut sched: ~Scheduler = Local::take();
-
-        // Assume that we need to continue idling unless we reach the
-        // end of this function without performing an action.
-        sched.idle_callback.get_mut_ref().resume();
-
-        // First we check for scheduler messages, these are higher
-        // priority than regular tasks.
-        let sched = match sched.interpret_message_queue(DontTryTooHard) {
-            Some(sched) => sched,
-            None => return
-        };
-
-        // This helper will use a randomized work-stealing algorithm
-        // to find work.
-        let sched = match sched.do_work() {
-            Some(sched) => sched,
-            None => return
-        };
-
-        // Now, before sleeping we need to find out if there really
-        // were any messages. Give it your best!
-        let mut sched = match sched.interpret_message_queue(GiveItYourBest) {
-            Some(sched) => sched,
-            None => return
-        };
-
-        // If we got here then there was no work to do.
-        // Generate a SchedHandle and push it to the sleeper list so
-        // somebody can wake us up later.
-        if !sched.sleepy && !sched.no_sleep {
-            rtdebug!("scheduler has no work to do, going to sleep");
-            sched.sleepy = true;
-            let handle = sched.make_handle();
-            sched.sleeper_list.push(handle);
-            // Since we are sleeping, deactivate the idle callback.
-            sched.idle_callback.get_mut_ref().pause();
-        } else {
-            rtdebug!("not sleeping, already doing so or no_sleep set");
-            // We may not be sleeping, but we still need to deactivate
-            // the idle callback.
-            sched.idle_callback.get_mut_ref().pause();
-        }
-
-        // Finished a cycle without using the Scheduler. Place it back
-        // in TLS.
-        Local::put(sched);
-    }
-
-    // This function returns None if the scheduler is "used", or it
-    // returns the still-available scheduler. At this point all
-    // message-handling will count as a turn of work, and as a result
-    // return None.
-    fn interpret_message_queue(mut ~self, effort: EffortLevel) -> Option<~Scheduler> {
-
-        let msg = if effort == DontTryTooHard {
-            self.message_queue.casual_pop()
-        } else {
-            // When popping our message queue, we could see an "inconsistent"
-            // state which means that we *should* be able to pop data, but we
-            // are unable to at this time. Our options are:
-            //
-            //  1. Spin waiting for data
-            //  2. Ignore this and pretend we didn't find a message
-            //
-            // If we choose route 1, then if the pusher in question is currently
-            // pre-empted, we're going to take up our entire time slice just
-            // spinning on this queue. If we choose route 2, then the pusher in
-            // question is still guaranteed to make a send() on its async
-            // handle, so we will guaranteed wake up and see its message at some
-            // point.
-            //
-            // I have chosen to take route #2.
-            match self.message_queue.pop() {
-                mpsc::Data(t) => Some(t),
-                mpsc::Empty | mpsc::Inconsistent => None
-            }
-        };
-
-        match msg {
-            Some(PinnedTask(task)) => {
-                let mut task = task;
-                task.give_home(Sched(self.make_handle()));
-                self.resume_task_immediately(task);
-                return None;
-            }
-            Some(TaskFromFriend(task)) => {
-                rtdebug!("got a task from a friend. lovely!");
-                self.process_task(task, Scheduler::resume_task_immediately_cl);
-                return None;
-            }
-            Some(RunOnce(task)) => {
-                // bypass the process_task logic to force running this task once
-                // on this home scheduler. This is often used for I/O (homing).
-                Scheduler::resume_task_immediately_cl(self, task);
-                return None;
-            }
-            Some(Wake) => {
-                self.sleepy = false;
-                Local::put(self);
-                return None;
-            }
-            Some(Shutdown) => {
-                rtdebug!("shutting down");
-                if self.sleepy {
-                    // There may be an outstanding handle on the
-                    // sleeper list.  Pop them all to make sure that's
-                    // not the case.
-                    loop {
-                        match self.sleeper_list.pop() {
-                            Some(handle) => {
-                                let mut handle = handle;
-                                handle.send(Wake);
-                            }
-                            None => break
-                        }
-                    }
-                }
-                // No more sleeping. After there are no outstanding
-                // event loop references we will shut down.
-                self.no_sleep = true;
-                self.sleepy = false;
-                Local::put(self);
-                return None;
-            }
-            None => {
-                return Some(self);
-            }
-        }
-    }
-
-    fn do_work(mut ~self) -> Option<~Scheduler> {
-        rtdebug!("scheduler calling do work");
-        match self.find_work() {
-            Some(task) => {
-                rtdebug!("found some work! processing the task");
-                self.process_task(task, Scheduler::resume_task_immediately_cl);
-                return None;
-            }
-            None => {
-                rtdebug!("no work was found, returning the scheduler struct");
-                return Some(self);
-            }
-        }
-    }
-
-    // Workstealing: In this iteration of the runtime each scheduler
-    // thread has a distinct work queue. When no work is available
-    // locally, make a few attempts to steal work from the queues of
-    // other scheduler threads. If a few steals fail we end up in the
-    // old "no work" path which is fine.
-
-    // First step in the process is to find a task. This function does
-    // that by first checking the local queue, and if there is no work
-    // there, trying to steal from the remote work queues.
-    fn find_work(&mut self) -> Option<~Task> {
-        rtdebug!("scheduler looking for work");
-        if !self.steal_for_yield {
-            match self.work_queue.pop() {
-                Some(task) => {
-                    rtdebug!("found a task locally");
-                    return Some(task)
-                }
-                None => {
-                    rtdebug!("scheduler trying to steal");
-                    return self.try_steals();
-                }
-            }
-        } else {
-            // During execution of the last task, it performed a 'yield',
-            // so we're doing some work stealing in order to introduce some
-            // scheduling randomness. Otherwise we would just end up popping
-            // that same task again. This is pretty lame and is to work around
-            // the problem that work stealing is not designed for 'non-strict'
-            // (non-fork-join) task parallelism.
-            self.steal_for_yield = false;
-            match self.try_steals() {
-                Some(task) => {
-                    rtdebug!("stole a task after yielding");
-                    return Some(task);
-                }
-                None => {
-                    rtdebug!("did not steal a task after yielding");
-                    // Back to business
-                    return self.find_work();
-                }
-            }
-        }
-    }
-
-    // Try stealing from all queues the scheduler knows about. This
-    // naive implementation can steal from our own queue or from other
-    // special schedulers.
-    fn try_steals(&mut self) -> Option<~Task> {
-        let work_queues = &mut self.work_queues;
-        let len = work_queues.len();
-        let start_index = self.rng.gen_range(0, len);
-        for index in range(0, len).map(|i| (i + start_index) % len) {
-            match work_queues[index].steal() {
-                deque::Data(task) => {
-                    rtdebug!("found task by stealing");
-                    return Some(task)
-                }
-                _ => ()
-            }
-        };
-        rtdebug!("giving up on stealing");
-        return None;
-    }
-
-    // * Task Routing Functions - Make sure tasks send up in the right
-    // place.
-
-    fn process_task(mut ~self, mut task: ~Task, schedule_fn: SchedulingFn) {
-        rtdebug!("processing a task");
-
-        let home = task.take_unwrap_home();
-        match home {
-            Sched(home_handle) => {
-                if home_handle.sched_id != self.sched_id() {
-                    rtdebug!("sending task home");
-                    task.give_home(Sched(home_handle));
-                    Scheduler::send_task_home(task);
-                    Local::put(self);
-                } else {
-                    rtdebug!("running task here");
-                    task.give_home(Sched(home_handle));
-                    schedule_fn(self, task);
-                }
-            }
-            AnySched if self.run_anything => {
-                rtdebug!("running anysched task here");
-                task.give_home(AnySched);
-                schedule_fn(self, task);
-            }
-            AnySched => {
-                rtdebug!("sending task to friend");
-                task.give_home(AnySched);
-                self.send_to_friend(task);
-                Local::put(self);
-            }
-        }
-    }
-
-    fn send_task_home(task: ~Task) {
-        let mut task = task;
-        let mut home = task.take_unwrap_home();
-        match home {
-            Sched(ref mut home_handle) => {
-                home_handle.send(PinnedTask(task));
-            }
-            AnySched => {
-                        rtabort!("error: cannot send anysched task home");
-            }
-        }
-    }
-
-    /// Take a non-homed task we aren't allowed to run here and send
-    /// it to the designated friend scheduler to execute.
-    fn send_to_friend(&mut self, task: ~Task) {
-        rtdebug!("sending a task to friend");
-        match self.friend_handle {
-            Some(ref mut handle) => {
-                handle.send(TaskFromFriend(task));
-            }
-            None => {
-                rtabort!("tried to send task to a friend but scheduler has no friends");
-            }
-        }
-    }
-
-    /// Schedule a task to be executed later.
-    ///
-    /// Pushes the task onto the work stealing queue and tells the
-    /// event loop to run it later. Always use this instead of pushing
-    /// to the work queue directly.
-    pub fn enqueue_task(&mut self, task: ~Task) {
-
-        // We push the task onto our local queue clone.
-        self.work_queue.push(task);
-        self.idle_callback.get_mut_ref().resume();
-
-        // We've made work available. Notify a
-        // sleeping scheduler.
-
-        match self.sleeper_list.casual_pop() {
-            Some(handle) => {
-                let mut handle = handle;
-                handle.send(Wake)
-            }
-            None => { (/* pass */) }
-        };
-    }
-
-    /// As enqueue_task, but with the possibility for the blocked task to
-    /// already have been killed.
-    pub fn enqueue_blocked_task(&mut self, blocked_task: BlockedTask) {
-        blocked_task.wake().map(|task| self.enqueue_task(task));
-    }
-
-    // * Core Context Switching Functions
-
-    // The primary function for changing contexts. In the current
-    // design the scheduler is just a slightly modified GreenTask, so
-    // all context swaps are from Task to Task. The only difference
-    // between the various cases is where the inputs come from, and
-    // what is done with the resulting task. That is specified by the
-    // cleanup function f, which takes the scheduler and the
-    // old task as inputs.
-
-    pub fn change_task_context(mut ~self,
-                               next_task: ~Task,
-                               f: |&mut Scheduler, ~Task|) {
-        // The current task is grabbed from TLS, not taken as an input.
-        // Doing an unsafe_take to avoid writing back a null pointer -
-        // We're going to call `put` later to do that.
-        let current_task: ~Task = unsafe { Local::unsafe_take() };
-
-        // Check that the task is not in an atomically() section (e.g.,
-        // holding a pthread mutex, which could deadlock the scheduler).
-        current_task.death.assert_may_sleep();
-
-        // These transmutes do something fishy with a closure.
-        let f_fake_region = unsafe {
-            transmute::<|&mut Scheduler, ~Task|,
-                        |&mut Scheduler, ~Task|>(f)
-        };
-        let f_opaque = ClosureConverter::from_fn(f_fake_region);
-
-        // The current task is placed inside an enum with the cleanup
-        // function. This enum is then placed inside the scheduler.
-        self.cleanup_job = Some(CleanupJob::new(current_task, f_opaque));
-
-        // The scheduler is then placed inside the next task.
-        let mut next_task = next_task;
-        next_task.sched = Some(self);
-
-        // However we still need an internal mutable pointer to the
-        // original task. The strategy here was "arrange memory, then
-        // get pointers", so we crawl back up the chain using
-        // transmute to eliminate borrowck errors.
-        unsafe {
-
-            let sched: &mut Scheduler =
-                transmute_mut_region(*next_task.sched.get_mut_ref());
-
-            let current_task: &mut Task = match sched.cleanup_job {
-                Some(CleanupJob { task: ref task, .. }) => {
-                    let task_ptr: *~Task = task;
-                    transmute_mut_region(*transmute_mut_unsafe(task_ptr))
-                }
-                None => {
-                    rtabort!("no cleanup job");
-                }
-            };
-
-            let (current_task_context, next_task_context) =
-                Scheduler::get_contexts(current_task, next_task);
-
-            // Done with everything - put the next task in TLS. This
-            // works because due to transmute the borrow checker
-            // believes that we have no internal pointers to
-            // next_task.
-            Local::put(next_task);
-
-            // The raw context swap operation. The next action taken
-            // will be running the cleanup job from the context of the
-            // next task.
-            Context::swap(current_task_context, next_task_context);
-        }
-
-        // When the context swaps back to this task we immediately
-        // run the cleanup job, as expected by the previously called
-        // swap_contexts function.
-        unsafe {
-            let task: *mut Task = Local::unsafe_borrow();
-            (*task).sched.get_mut_ref().run_cleanup_job();
-
-            // See the comments in switch_running_tasks_and_then for why a lock
-            // is acquired here. This is the resumption points and the "bounce"
-            // that it is referring to.
-            (*task).nasty_deschedule_lock.lock();
-            (*task).nasty_deschedule_lock.unlock();
-        }
-    }
-
-    // Returns a mutable reference to both contexts involved in this
-    // swap. This is unsafe - we are getting mutable internal
-    // references to keep even when we don't own the tasks. It looks
-    // kinda safe because we are doing transmutes before passing in
-    // the arguments.
-    pub fn get_contexts<'a>(current_task: &mut Task, next_task: &mut Task) ->
-        (&'a mut Context, &'a mut Context) {
-        let current_task_context =
-            &mut current_task.coroutine.get_mut_ref().saved_context;
-        let next_task_context =
-                &mut next_task.coroutine.get_mut_ref().saved_context;
-        unsafe {
-            (transmute_mut_region(current_task_context),
-             transmute_mut_region(next_task_context))
-        }
-    }
-
-    // * Context Swapping Helpers - Here be ugliness!
-
-    pub fn resume_task_immediately(~self, task: ~Task) {
-        self.change_task_context(task, |sched, stask| {
-            sched.sched_task = Some(stask);
-        })
-    }
-
-    fn resume_task_immediately_cl(sched: ~Scheduler,
-                                  task: ~Task) {
-        sched.resume_task_immediately(task)
-    }
-
-
-    pub fn resume_blocked_task_immediately(~self, blocked_task: BlockedTask) {
-        match blocked_task.wake() {
-            Some(task) => { self.resume_task_immediately(task); }
-            None => Local::put(self)
-        };
-    }
-
-    /// Block a running task, context switch to the scheduler, then pass the
-    /// blocked task to a closure.
-    ///
-    /// # Safety note
-    ///
-    /// The closure here is a *stack* closure that lives in the
-    /// running task.  It gets transmuted to the scheduler's lifetime
-    /// and called while the task is blocked.
-    ///
-    /// This passes a Scheduler pointer to the fn after the context switch
-    /// in order to prevent that fn from performing further scheduling operations.
-    /// Doing further scheduling could easily result in infinite recursion.
-    ///
-    /// Note that if the closure provided relinquishes ownership of the
-    /// BlockedTask, then it is possible for the task to resume execution before
-    /// the closure has finished executing. This would naturally introduce a
-    /// race if the closure and task shared portions of the environment.
-    ///
-    /// This situation is currently prevented, or in other words it is
-    /// guaranteed that this function will not return before the given closure
-    /// has returned.
-    pub fn deschedule_running_task_and_then(mut ~self,
-                                            f: |&mut Scheduler, BlockedTask|) {
-        // Trickier - we need to get the scheduler task out of self
-        // and use it as the destination.
-        let stask = self.sched_task.take_unwrap();
-        // Otherwise this is the same as below.
-        self.switch_running_tasks_and_then(stask, f);
-    }
-
-    pub fn switch_running_tasks_and_then(~self, next_task: ~Task,
-                                         f: |&mut Scheduler, BlockedTask|) {
-        // And here comes one of the sad moments in which a lock is used in a
-        // core portion of the rust runtime. As always, this is highly
-        // undesirable, so there's a good reason behind it.
-        //
-        // There is an excellent outline of the problem in issue #8132, and it's
-        // summarized in that `f` is executed on a sched task, but its
-        // environment is on the previous task. If `f` relinquishes ownership of
-        // the BlockedTask, then it may introduce a race where `f` is using the
-        // environment as well as the code after the 'deschedule' block.
-        //
-        // The solution we have chosen to adopt for now is to acquire a
-        // task-local lock around this block. The resumption of the task in
-        // context switching will bounce on the lock, thereby waiting for this
-        // block to finish, eliminating the race mentioned above.
-        //
-        // To actually maintain a handle to the lock, we use an unsafe pointer
-        // to it, but we're guaranteed that the task won't exit until we've
-        // unlocked the lock so there's no worry of this memory going away.
-        self.change_task_context(next_task, |sched, mut task| {
-            let lock: *mut Mutex = &mut task.nasty_deschedule_lock;
-            unsafe { (*lock).lock() }
-            f(sched, BlockedTask::block(task));
-            unsafe { (*lock).unlock() }
-        })
-    }
-
-    fn switch_task(sched: ~Scheduler, task: ~Task) {
-        sched.switch_running_tasks_and_then(task, |sched, last_task| {
-            sched.enqueue_blocked_task(last_task);
-        });
-    }
-
-    // * Task Context Helpers
-
-    /// Called by a running task to end execution, after which it will
-    /// be recycled by the scheduler for reuse in a new task.
-    pub fn terminate_current_task(mut ~self) {
-        // Similar to deschedule running task and then, but cannot go through
-        // the task-blocking path. The task is already dying.
-        let stask = self.sched_task.take_unwrap();
-        self.change_task_context(stask, |sched, mut dead_task| {
-            let coroutine = dead_task.coroutine.take_unwrap();
-            coroutine.recycle(&mut sched.stack_pool);
-        })
-    }
-
-    pub fn run_task(task: ~Task) {
-        let sched: ~Scheduler = Local::take();
-        sched.process_task(task, Scheduler::switch_task);
-    }
-
-    pub fn run_task_later(next_task: ~Task) {
-        let mut sched = Local::borrow(None::<Scheduler>);
-        sched.get().enqueue_task(next_task);
-    }
-
-    /// Yield control to the scheduler, executing another task. This is guaranteed
-    /// to introduce some amount of randomness to the scheduler. Currently the
-    /// randomness is a result of performing a round of work stealing (which
-    /// may end up stealing from the current scheduler).
-    pub fn yield_now(mut ~self) {
-        self.yield_check_count = reset_yield_check(&mut self.rng);
-        // Tell the scheduler to start stealing on the next iteration
-        self.steal_for_yield = true;
-        self.deschedule_running_task_and_then(|sched, task| {
-            sched.enqueue_blocked_task(task);
-        })
-    }
-
-    pub fn maybe_yield(mut ~self) {
-        // The number of times to do the yield check before yielding, chosen arbitrarily.
-        rtassert!(self.yield_check_count > 0);
-        self.yield_check_count -= 1;
-        if self.yield_check_count == 0 {
-            self.yield_now();
-        } else {
-            Local::put(self);
-        }
-    }
-
-
-    // * Utility Functions
-
-    pub fn sched_id(&self) -> uint { to_uint(self) }
-
-    pub fn run_cleanup_job(&mut self) {
-        let cleanup_job = self.cleanup_job.take_unwrap();
-        cleanup_job.run(self);
-    }
-
-    pub fn make_handle(&mut self) -> SchedHandle {
-        let remote = self.event_loop.remote_callback(~SchedRunner as ~Callback);
-
-        return SchedHandle {
-            remote: remote,
-            queue: self.message_producer.clone(),
-            sched_id: self.sched_id()
-        };
-    }
-}
-
-// Supporting types
-
-type SchedulingFn = extern "Rust" fn (~Scheduler, ~Task);
-
-pub enum SchedMessage {
-    Wake,
-    Shutdown,
-    PinnedTask(~Task),
-    TaskFromFriend(~Task),
-    RunOnce(~Task),
-}
-
-pub struct SchedHandle {
-    priv remote: ~RemoteCallback,
-    priv queue: mpsc::Producer<SchedMessage, ()>,
-    sched_id: uint
-}
-
-impl SchedHandle {
-    pub fn send(&mut self, msg: SchedMessage) {
-        self.queue.push(msg);
-        self.remote.fire();
-    }
-}
-
-struct SchedRunner;
-
-impl Callback for SchedRunner {
-    fn call(&mut self) {
-        Scheduler::run_sched_once();
-    }
-}
-
-struct CleanupJob {
-    task: ~Task,
-    f: UnsafeTaskReceiver
-}
-
-impl CleanupJob {
-    pub fn new(task: ~Task, f: UnsafeTaskReceiver) -> CleanupJob {
-        CleanupJob {
-            task: task,
-            f: f
-        }
-    }
-
-    pub fn run(self, sched: &mut Scheduler) {
-        let CleanupJob { task: task, f: f } = self;
-        f.to_fn()(sched, task)
-    }
-}
-
-// XXX: Some hacks to put a || closure in Scheduler without borrowck
-// complaining
-type UnsafeTaskReceiver = raw::Closure;
-trait ClosureConverter {
-    fn from_fn(|&mut Scheduler, ~Task|) -> Self;
-    fn to_fn(self) -> |&mut Scheduler, ~Task|;
-}
-impl ClosureConverter for UnsafeTaskReceiver {
-    fn from_fn(f: |&mut Scheduler, ~Task|) -> UnsafeTaskReceiver {
-        unsafe { transmute(f) }
-    }
-    fn to_fn(self) -> |&mut Scheduler, ~Task| { unsafe { transmute(self) } }
-}
-
-// On unix, we read randomness straight from /dev/urandom, but the
-// default constructor of an XorShiftRng does this via io::fs, which
-// relies on the scheduler existing, so we have to manually load
-// randomness. Windows has its own C API for this, so we don't need to
-// worry there.
-#[cfg(windows)]
-fn new_sched_rng() -> XorShiftRng {
-    XorShiftRng::new()
-}
-#[cfg(unix)]
-fn new_sched_rng() -> XorShiftRng {
-    use libc;
-    use mem;
-    use c_str::ToCStr;
-    use vec::MutableVector;
-    use iter::Iterator;
-    use rand::SeedableRng;
-
-    let fd = "/dev/urandom".with_c_str(|name| {
-        unsafe { libc::open(name, libc::O_RDONLY, 0) }
-    });
-    if fd == -1 {
-        rtabort!("could not open /dev/urandom for reading.")
-    }
-
-    let mut seeds = [0u32, .. 4];
-    let size = mem::size_of_val(&seeds);
-    loop {
-        let nbytes = unsafe {
-            libc::read(fd,
-                       seeds.as_mut_ptr() as *mut libc::c_void,
-                       size as libc::size_t)
-        };
-        rtassert!(nbytes as uint == size);
-
-        if !seeds.iter().all(|x| *x == 0) {
-            break;
-        }
-    }
-
-    unsafe {libc::close(fd);}
-
-    SeedableRng::from_seed(seeds)
-}
-
-#[cfg(test)]
-mod test {
-    use prelude::*;
-
-    use borrow::to_uint;
-    use rt::deque::BufferPool;
-    use rt::basic;
-    use rt::sched::{Scheduler};
-    use rt::task::{Task, Sched};
-    use rt::test::*;
-    use rt::thread::Thread;
-    use rt::util;
-    use task::TaskResult;
-    use unstable::run_in_bare_thread;
-
-    #[test]
-    fn trivial_run_in_newsched_task_test() {
-        let mut task_ran = false;
-        let task_ran_ptr: *mut bool = &mut task_ran;
-        do run_in_newsched_task || {
-            unsafe { *task_ran_ptr = true };
-            rtdebug!("executed from the new scheduler")
-        }
-        assert!(task_ran);
-    }
-
-    #[test]
-    fn multiple_task_test() {
-        let total = 10;
-        let mut task_run_count = 0;
-        let task_run_count_ptr: *mut uint = &mut task_run_count;
-        do run_in_newsched_task || {
-            for _ in range(0u, total) {
-                do spawntask || {
-                    unsafe { *task_run_count_ptr = *task_run_count_ptr + 1};
-                }
-            }
-        }
-        assert!(task_run_count == total);
-    }
-
-    #[test]
-    fn multiple_task_nested_test() {
-        let mut task_run_count = 0;
-        let task_run_count_ptr: *mut uint = &mut task_run_count;
-        do run_in_newsched_task || {
-            do spawntask || {
-                unsafe { *task_run_count_ptr = *task_run_count_ptr + 1 };
-                do spawntask || {
-                    unsafe { *task_run_count_ptr = *task_run_count_ptr + 1 };
-                    do spawntask || {
-                        unsafe { *task_run_count_ptr = *task_run_count_ptr + 1 };
-                    }
-                }
-            }
-        }
-        assert!(task_run_count == 3);
-    }
-
-    // Confirm that a sched_id actually is the uint form of the
-    // pointer to the scheduler struct.
-    #[test]
-    fn simple_sched_id_test() {
-        do run_in_bare_thread {
-            let sched = ~new_test_uv_sched();
-            assert!(to_uint(sched) == sched.sched_id());
-        }
-    }
-
-    // Compare two scheduler ids that are different, this should never
-    // fail but may catch a mistake someday.
-    #[test]
-    fn compare_sched_id_test() {
-        do run_in_bare_thread {
-            let sched_one = ~new_test_uv_sched();
-            let sched_two = ~new_test_uv_sched();
-            assert!(sched_one.sched_id() != sched_two.sched_id());
-        }
-    }
-
-
-    // A very simple test that confirms that a task executing on the
-    // home scheduler notices that it is home.
-    #[test]
-    fn test_home_sched() {
-        do run_in_bare_thread {
-            let mut task_ran = false;
-            let task_ran_ptr: *mut bool = &mut task_ran;
-
-            let mut sched = ~new_test_uv_sched();
-            let sched_handle = sched.make_handle();
-
-            let mut task = ~do Task::new_root_homed(&mut sched.stack_pool, None,
-                                                Sched(sched_handle)) {
-                unsafe { *task_ran_ptr = true };
-                assert!(Task::on_appropriate_sched());
-            };
-
-            let on_exit: proc(TaskResult) = proc(exit_status) {
-                rtassert!(exit_status.is_ok())
-            };
-            task.death.on_exit = Some(on_exit);
-
-            sched.bootstrap(task);
-        }
-    }
-
-    // An advanced test that checks all four possible states that a
-    // (task,sched) can be in regarding homes.
-
-    #[test]
-    fn test_schedule_home_states() {
-        use rt::sleeper_list::SleeperList;
-        use rt::sched::Shutdown;
-        use borrow;
-
-        do run_in_bare_thread {
-
-            let sleepers = SleeperList::new();
-            let mut pool = BufferPool::new();
-            let (normal_worker, normal_stealer) = pool.deque();
-            let (special_worker, special_stealer) = pool.deque();
-            let queues = ~[normal_stealer, special_stealer];
-
-            // Our normal scheduler
-            let mut normal_sched = ~Scheduler::new(
-                basic::event_loop(),
-                normal_worker,
-                queues.clone(),
-                sleepers.clone());
-
-            let normal_handle = normal_sched.make_handle();
-
-            let friend_handle = normal_sched.make_handle();
-
-            // Our special scheduler
-            let mut special_sched = ~Scheduler::new_special(
-                basic::event_loop(),
-                special_worker,
-                queues.clone(),
-                sleepers.clone(),
-                false,
-                Some(friend_handle));
-
-            let special_handle = special_sched.make_handle();
-
-            let t1_handle = special_sched.make_handle();
-            let t4_handle = special_sched.make_handle();
-
-            // Four test tasks:
-            //   1) task is home on special
-            //   2) task not homed, sched doesn't care
-            //   3) task not homed, sched requeues
-            //   4) task not home, send home
-
-            let task1 = ~do Task::new_root_homed(&mut special_sched.stack_pool, None,
-                                                 Sched(t1_handle)) || {
-                rtassert!(Task::on_appropriate_sched());
-            };
-            rtdebug!("task1 id: **{}**", borrow::to_uint(task1));
-
-            let task2 = ~do Task::new_root(&mut normal_sched.stack_pool, None) {
-                rtassert!(Task::on_appropriate_sched());
-            };
-
-            let task3 = ~do Task::new_root(&mut normal_sched.stack_pool, None) {
-                rtassert!(Task::on_appropriate_sched());
-            };
-
-            let task4 = ~do Task::new_root_homed(&mut special_sched.stack_pool, None,
-                                                 Sched(t4_handle)) {
-                rtassert!(Task::on_appropriate_sched());
-            };
-            rtdebug!("task4 id: **{}**", borrow::to_uint(task4));
-
-            // Signal from the special task that we are done.
-            let (port, chan) = Chan::<()>::new();
-
-            let normal_task = ~do Task::new_root(&mut normal_sched.stack_pool, None) {
-                rtdebug!("*about to submit task2*");
-                Scheduler::run_task(task2);
-                rtdebug!("*about to submit task4*");
-                Scheduler::run_task(task4);
-                rtdebug!("*normal_task done*");
-                port.recv();
-                let mut nh = normal_handle;
-                nh.send(Shutdown);
-                let mut sh = special_handle;
-                sh.send(Shutdown);
-            };
-
-            rtdebug!("normal task: {}", borrow::to_uint(normal_task));
-
-            let special_task = ~do Task::new_root(&mut special_sched.stack_pool, None) {
-                rtdebug!("*about to submit task1*");
-                Scheduler::run_task(task1);
-                rtdebug!("*about to submit task3*");
-                Scheduler::run_task(task3);
-                rtdebug!("*done with special_task*");
-                chan.send(());
-            };
-
-            rtdebug!("special task: {}", borrow::to_uint(special_task));
-
-            let normal_sched = normal_sched;
-            let normal_thread = do Thread::start {
-                normal_sched.bootstrap(normal_task);
-                rtdebug!("finished with normal_thread");
-            };
-
-            let special_sched = special_sched;
-            let special_thread = do Thread::start {
-                special_sched.bootstrap(special_task);
-                rtdebug!("finished with special_sched");
-            };
-
-            normal_thread.join();
-            special_thread.join();
-        }
-    }
-
-    #[test]
-    fn test_stress_schedule_task_states() {
-        if util::limit_thread_creation_due_to_osx_and_valgrind() { return; }
-        let n = stress_factor() * 120;
-        for _ in range(0, n as int) {
-            test_schedule_home_states();
-        }
-    }
-
-    #[test]
-    fn test_io_callback() {
-        use io::timer;
-
-        // This is a regression test that when there are no schedulable tasks
-        // in the work queue, but we are performing I/O, that once we do put
-        // something in the work queue again the scheduler picks it up and doesn't
-        // exit before emptying the work queue
-        do run_in_uv_task {
-            do spawntask {
-                timer::sleep(10);
-            }
-        }
-    }
-
-    #[test]
-    fn handle() {
-        do run_in_bare_thread {
-            let (port, chan) = Chan::new();
-
-            let thread_one = do Thread::start {
-                let chan = chan;
-                do run_in_newsched_task_core {
-                    chan.send(());
-                }
-            };
-
-            let thread_two = do Thread::start {
-                let port = port;
-                do run_in_newsched_task_core {
-                    port.recv();
-                }
-            };
-
-            thread_two.join();
-            thread_one.join();
-        }
-    }
-
-    // A regression test that the final message is always handled.
-    // Used to deadlock because Shutdown was never recvd.
-    #[test]
-    fn no_missed_messages() {
-        use rt::sleeper_list::SleeperList;
-        use rt::stack::StackPool;
-        use rt::sched::{Shutdown, TaskFromFriend};
-
-        do run_in_bare_thread {
-            stress_factor().times(|| {
-                let sleepers = SleeperList::new();
-                let mut pool = BufferPool::new();
-                let (worker, stealer) = pool.deque();
-
-                let mut sched = ~Scheduler::new(
-                    basic::event_loop(),
-                    worker,
-                    ~[stealer],
-                    sleepers.clone());
-
-                let mut handle = sched.make_handle();
-
-                let sched = sched;
-                let thread = do Thread::start {
-                    let mut sched = sched;
-                    let bootstrap_task =
-                        ~Task::new_root(&mut sched.stack_pool,
-                                        None,
-                                        proc()());
-                    sched.bootstrap(bootstrap_task);
-                };
-
-                let mut stack_pool = StackPool::new();
-                let task = ~Task::new_root(&mut stack_pool, None, proc()());
-                handle.send(TaskFromFriend(task));
-
-                handle.send(Shutdown);
-                drop(handle);
-
-                thread.join();
-            })
-        }
-    }
-
-    #[test]
-    fn multithreading() {
-        use num::Times;
-        use vec::OwnedVector;
-        use container::Container;
-
-        do run_in_mt_newsched_task {
-            let mut ports = ~[];
-            10.times(|| {
-                let (port, chan) = Chan::new();
-                do spawntask_later {
-                    chan.send(());
-                }
-                ports.push(port);
-            });
-
-            while !ports.is_empty() {
-                ports.pop().recv();
-            }
-        }
-    }
-
-     #[test]
-    fn thread_ring() {
-        do run_in_mt_newsched_task {
-            let (end_port, end_chan) = Chan::new();
-
-            let n_tasks = 10;
-            let token = 2000;
-
-            let (mut p, ch1) = Chan::new();
-            ch1.send((token, end_chan));
-            let mut i = 2;
-            while i <= n_tasks {
-                let (next_p, ch) = Chan::new();
-                let imm_i = i;
-                let imm_p = p;
-                do spawntask_random {
-                    roundtrip(imm_i, n_tasks, &imm_p, &ch);
-                };
-                p = next_p;
-                i += 1;
-            }
-            let p = p;
-            do spawntask_random {
-                roundtrip(1, n_tasks, &p, &ch1);
-            }
-
-            end_port.recv();
-        }
-
-        fn roundtrip(id: int, n_tasks: int,
-                     p: &Port<(int, Chan<()>)>,
-                     ch: &Chan<(int, Chan<()>)>) {
-            while (true) {
-                match p.recv() {
-                    (1, end_chan) => {
-                        debug!("{}\n", id);
-                        end_chan.send(());
-                        return;
-                    }
-                    (token, end_chan) => {
-                        debug!("thread: {}   got token: {}", id, token);
-                        ch.send((token - 1, end_chan));
-                        if token <= n_tasks {
-                            return;
-                        }
-                    }
-                }
-            }
-        }
-    }
-
-    #[test]
-    fn start_closure_dtor() {
-        use ops::Drop;
-
-        // Regression test that the `start` task entrypoint can
-        // contain dtors that use task resources
-        do run_in_newsched_task {
-            struct S { field: () }
-
-            impl Drop for S {
-                fn drop(&mut self) {
-                    let _foo = @0;
-                }
-            }
-
-            let s = S { field: () };
-
-            do spawntask {
-                let _ss = &s;
-            }
-        }
-    }
-
-    // FIXME: #9407: xfail-test
-    #[ignore]
-    #[test]
-    fn dont_starve_1() {
-        stress_factor().times(|| {
-            do run_in_mt_newsched_task {
-                let (port, chan) = Chan::new();
-
-                // This task should not be able to starve the sender;
-                // The sender should get stolen to another thread.
-                do spawntask {
-                    while port.try_recv().is_none() { }
-                }
-
-                chan.send(());
-            }
-        })
-    }
-
-    #[test]
-    fn dont_starve_2() {
-        stress_factor().times(|| {
-            do run_in_newsched_task {
-                let (port, chan) = Chan::new();
-                let (_port2, chan2) = Chan::new();
-
-                // This task should not be able to starve the other task.
-                // The sends should eventually yield.
-                do spawntask {
-                    while port.try_recv().is_none() {
-                        chan2.send(());
-                    }
-                }
-
-                chan.send(());
-            }
-        })
-    }
-
-    // Regression test for a logic bug that would cause single-threaded schedulers
-    // to sleep forever after yielding and stealing another task.
-    #[test]
-    fn single_threaded_yield() {
-        use task::{spawn, spawn_sched, SingleThreaded, deschedule};
-        use num::Times;
-
-        do spawn_sched(SingleThreaded) {
-            5.times(|| { deschedule(); })
-        }
-        do spawn { }
-        do spawn { }
-    }
-}
diff --git a/src/libstd/rt/sleeper_list.rs b/src/libstd/rt/sleeper_list.rs
deleted file mode 100644
index 39c7431837f..00000000000
--- a/src/libstd/rt/sleeper_list.rs
+++ /dev/null
@@ -1,47 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! Maintains a shared list of sleeping schedulers. Schedulers
-//! use this to wake each other up.
-
-use rt::sched::SchedHandle;
-use rt::mpmc_bounded_queue::Queue;
-use option::*;
-use clone::Clone;
-
-pub struct SleeperList {
-    priv q: Queue<SchedHandle>,
-}
-
-impl SleeperList {
-    pub fn new() -> SleeperList {
-        SleeperList{q: Queue::with_capacity(8*1024)}
-    }
-
-    pub fn push(&mut self, value: SchedHandle) {
-        assert!(self.q.push(value))
-    }
-
-    pub fn pop(&mut self) -> Option<SchedHandle> {
-        self.q.pop()
-    }
-
-    pub fn casual_pop(&mut self) -> Option<SchedHandle> {
-        self.q.pop()
-    }
-}
-
-impl Clone for SleeperList {
-    fn clone(&self) -> SleeperList {
-        SleeperList {
-            q: self.q.clone()
-        }
-    }
-}
diff --git a/src/libstd/rt/spsc_queue.rs b/src/libstd/rt/spsc_queue.rs
deleted file mode 100644
index f14533d726a..00000000000
--- a/src/libstd/rt/spsc_queue.rs
+++ /dev/null
@@ -1,296 +0,0 @@
-/* Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- *    1. Redistributions of source code must retain the above copyright notice,
- *       this list of conditions and the following disclaimer.
- *
- *    2. Redistributions in binary form must reproduce the above copyright
- *       notice, this list of conditions and the following disclaimer in the
- *       documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
- * SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
- * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * The views and conclusions contained in the software and documentation are
- * those of the authors and should not be interpreted as representing official
- * policies, either expressed or implied, of Dmitry Vyukov.
- */
-
-// http://www.1024cores.net/home/lock-free-algorithms/queues/unbounded-spsc-queue
-use cast;
-use kinds::Send;
-use ops::Drop;
-use option::{Some, None, Option};
-use unstable::atomics::{AtomicPtr, Relaxed, AtomicUint, Acquire, Release};
-use unstable::sync::UnsafeArc;
-
-// Node within the linked list queue of messages to send
-struct Node<T> {
-    // XXX: this could be an uninitialized T if we're careful enough, and
-    //      that would reduce memory usage (and be a bit faster).
-    //      is it worth it?
-    value: Option<T>,           // nullable for re-use of nodes
-    next: AtomicPtr<Node<T>>,   // next node in the queue
-}
-
-// The producer/consumer halves both need access to the `tail` field, and if
-// they both have access to that we may as well just give them both access
-// to this whole structure.
-struct State<T, P> {
-    // consumer fields
-    tail: *mut Node<T>, // where to pop from
-    tail_prev: AtomicPtr<Node<T>>, // where to pop from
-
-    // producer fields
-    head: *mut Node<T>,      // where to push to
-    first: *mut Node<T>,     // where to get new nodes from
-    tail_copy: *mut Node<T>, // between first/tail
-
-    // Cache maintenance fields. Additions and subtractions are stored
-    // separately in order to allow them to use nonatomic addition/subtraction.
-    cache_bound: uint,
-    cache_additions: AtomicUint,
-    cache_subtractions: AtomicUint,
-
-    packet: P,
-}
-
-pub struct Producer<T, P> {
-    priv state: UnsafeArc<State<T, P>>,
-}
-
-pub struct Consumer<T, P> {
-    priv state: UnsafeArc<State<T, P>>,
-}
-
-pub fn queue<T: Send, P: Send>(bound: uint,
-                               p: P) -> (Consumer<T, P>, Producer<T, P>)
-{
-    let n1 = Node::new();
-    let n2 = Node::new();
-    unsafe { (*n1).next.store(n2, Relaxed) }
-    let state = State {
-        tail: n2,
-        tail_prev: AtomicPtr::new(n1),
-        head: n2,
-        first: n1,
-        tail_copy: n1,
-        cache_bound: bound,
-        cache_additions: AtomicUint::new(0),
-        cache_subtractions: AtomicUint::new(0),
-        packet: p,
-    };
-    let (arc1, arc2) = UnsafeArc::new2(state);
-    (Consumer { state: arc1 }, Producer { state: arc2 })
-}
-
-impl<T: Send> Node<T> {
-    fn new() -> *mut Node<T> {
-        unsafe {
-            cast::transmute(~Node {
-                value: None,
-                next: AtomicPtr::new(0 as *mut Node<T>),
-            })
-        }
-    }
-}
-
-impl<T: Send, P: Send> Producer<T, P> {
-    pub fn push(&mut self, t: T) {
-        unsafe { (*self.state.get()).push(t) }
-    }
-    pub fn is_empty(&self) -> bool {
-        unsafe { (*self.state.get()).is_empty() }
-    }
-    pub unsafe fn packet(&self) -> *mut P {
-        &mut (*self.state.get()).packet as *mut P
-    }
-}
-
-impl<T: Send, P: Send> Consumer<T, P> {
-    pub fn pop(&mut self) -> Option<T> {
-        unsafe { (*self.state.get()).pop() }
-    }
-    pub unsafe fn packet(&self) -> *mut P {
-        &mut (*self.state.get()).packet as *mut P
-    }
-}
-
-impl<T: Send, P: Send> State<T, P> {
-    // remember that there is only one thread executing `push` (and only one
-    // thread executing `pop`)
-    unsafe fn push(&mut self, t: T) {
-        // Acquire a node (which either uses a cached one or allocates a new
-        // one), and then append this to the 'head' node.
-        let n = self.alloc();
-        assert!((*n).value.is_none());
-        (*n).value = Some(t);
-        (*n).next.store(0 as *mut Node<T>, Relaxed);
-        (*self.head).next.store(n, Release);
-        self.head = n;
-    }
-
-    unsafe fn alloc(&mut self) -> *mut Node<T> {
-        // First try to see if we can consume the 'first' node for our uses.
-        // We try to avoid as many atomic instructions as possible here, so
-        // the addition to cache_subtractions is not atomic (plus we're the
-        // only one subtracting from the cache).
-        if self.first != self.tail_copy {
-            if self.cache_bound > 0 {
-                let b = self.cache_subtractions.load(Relaxed);
-                self.cache_subtractions.store(b + 1, Relaxed);
-            }
-            let ret = self.first;
-            self.first = (*ret).next.load(Relaxed);
-            return ret;
-        }
-        // If the above fails, then update our copy of the tail and try
-        // again.
-        self.tail_copy = self.tail_prev.load(Acquire);
-        if self.first != self.tail_copy {
-            if self.cache_bound > 0 {
-                let b = self.cache_subtractions.load(Relaxed);
-                self.cache_subtractions.store(b + 1, Relaxed);
-            }
-            let ret = self.first;
-            self.first = (*ret).next.load(Relaxed);
-            return ret;
-        }
-        // If all of that fails, then we have to allocate a new node
-        // (there's nothing in the node cache).
-        Node::new()
-    }
-
-    // remember that there is only one thread executing `pop` (and only one
-    // thread executing `push`)
-    unsafe fn pop(&mut self) -> Option<T> {
-        // The `tail` node is not actually a used node, but rather a
-        // sentinel from where we should start popping from. Hence, look at
-        // tail's next field and see if we can use it. If we do a pop, then
-        // the current tail node is a candidate for going into the cache.
-        let tail = self.tail;
-        let next = (*tail).next.load(Acquire);
-        if next.is_null() { return None }
-        assert!((*next).value.is_some());
-        let ret = (*next).value.take();
-
-        self.tail = next;
-        if self.cache_bound == 0 {
-            self.tail_prev.store(tail, Release);
-        } else {
-            // XXX: this is dubious with overflow.
-            let additions = self.cache_additions.load(Relaxed);
-            let subtractions = self.cache_subtractions.load(Relaxed);
-            let size = additions - subtractions;
-
-            if size < self.cache_bound {
-                self.tail_prev.store(tail, Release);
-                self.cache_additions.store(additions + 1, Relaxed);
-            } else {
-                (*self.tail_prev.load(Relaxed)).next.store(next, Relaxed);
-                // We have successfully erased all references to 'tail', so
-                // now we can safely drop it.
-                let _: ~Node<T> = cast::transmute(tail);
-            }
-        }
-        return ret;
-    }
-
-    unsafe fn is_empty(&self) -> bool {
-        let tail = self.tail;
-        let next = (*tail).next.load(Acquire);
-        return next.is_null();
-    }
-}
-
-#[unsafe_destructor]
-impl<T: Send, P: Send> Drop for State<T, P> {
-    fn drop(&mut self) {
-        unsafe {
-            let mut cur = self.first;
-            while !cur.is_null() {
-                let next = (*cur).next.load(Relaxed);
-                let _n: ~Node<T> = cast::transmute(cur);
-                cur = next;
-            }
-        }
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use prelude::*;
-    use super::queue;
-    use task;
-
-    #[test]
-    fn smoke() {
-        let (mut c, mut p) = queue(0, ());
-        p.push(1);
-        p.push(2);
-        assert_eq!(c.pop(), Some(1));
-        assert_eq!(c.pop(), Some(2));
-        assert_eq!(c.pop(), None);
-        p.push(3);
-        p.push(4);
-        assert_eq!(c.pop(), Some(3));
-        assert_eq!(c.pop(), Some(4));
-        assert_eq!(c.pop(), None);
-    }
-
-    #[test]
-    fn drop_full() {
-        let (_, mut p) = queue(0, ());
-        p.push(~1);
-        p.push(~2);
-    }
-
-    #[test]
-    fn smoke_bound() {
-        let (mut c, mut p) = queue(1, ());
-        p.push(1);
-        p.push(2);
-        assert_eq!(c.pop(), Some(1));
-        assert_eq!(c.pop(), Some(2));
-        assert_eq!(c.pop(), None);
-        p.push(3);
-        p.push(4);
-        assert_eq!(c.pop(), Some(3));
-        assert_eq!(c.pop(), Some(4));
-        assert_eq!(c.pop(), None);
-    }
-
-    #[test]
-    fn stress() {
-        stress_bound(0);
-        stress_bound(1);
-
-        fn stress_bound(bound: uint) {
-            let (c, mut p) = queue(bound, ());
-            do task::spawn_sched(task::SingleThreaded) {
-                let mut c = c;
-                for _ in range(0, 100000) {
-                    loop {
-                        match c.pop() {
-                            Some(1) => break,
-                            Some(_) => fail!(),
-                            None => {}
-                        }
-                    }
-                }
-            }
-            for _ in range(0, 100000) {
-                p.push(1);
-            }
-        }
-    }
-}
diff --git a/src/libstd/rt/stack.rs b/src/libstd/rt/stack.rs
deleted file mode 100644
index 44b60e955d2..00000000000
--- a/src/libstd/rt/stack.rs
+++ /dev/null
@@ -1,78 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-use container::Container;
-use ptr::RawPtr;
-use vec;
-use ops::Drop;
-use libc::{c_uint, uintptr_t};
-
-pub struct StackSegment {
-    priv buf: ~[u8],
-    priv valgrind_id: c_uint
-}
-
-impl StackSegment {
-    pub fn new(size: uint) -> StackSegment {
-        unsafe {
-            // Crate a block of uninitialized values
-            let mut stack = vec::with_capacity(size);
-            stack.set_len(size);
-
-            let mut stk = StackSegment {
-                buf: stack,
-                valgrind_id: 0
-            };
-
-            // XXX: Using the FFI to call a C macro. Slow
-            stk.valgrind_id = rust_valgrind_stack_register(stk.start(), stk.end());
-            return stk;
-        }
-    }
-
-    /// Point to the low end of the allocated stack
-    pub fn start(&self) -> *uint {
-        self.buf.as_ptr() as *uint
-    }
-
-    /// Point one word beyond the high end of the allocated stack
-    pub fn end(&self) -> *uint {
-        unsafe {
-            self.buf.as_ptr().offset(self.buf.len() as int) as *uint
-        }
-    }
-}
-
-impl Drop for StackSegment {
-    fn drop(&mut self) {
-        unsafe {
-            // XXX: Using the FFI to call a C macro. Slow
-            rust_valgrind_stack_deregister(self.valgrind_id);
-        }
-    }
-}
-
-pub struct StackPool(());
-
-impl StackPool {
-    pub fn new() -> StackPool { StackPool(()) }
-
-    fn take_segment(&self, min_size: uint) -> StackSegment {
-        StackSegment::new(min_size)
-    }
-
-    fn give_segment(&self, _stack: StackSegment) {
-    }
-}
-
-extern {
-    fn rust_valgrind_stack_register(start: *uintptr_t, end: *uintptr_t) -> c_uint;
-    fn rust_valgrind_stack_deregister(id: c_uint);
-}
diff --git a/src/libstd/rt/task.rs b/src/libstd/rt/task.rs
index 30e05e9091f..e6ab159a769 100644
--- a/src/libstd/rt/task.rs
+++ b/src/libstd/rt/task.rs
@@ -13,29 +13,41 @@
 //! local storage, and logging. Even a 'freestanding' Rust would likely want
 //! to implement this.
 
-use super::local_heap::LocalHeap;
-
-use prelude::*;
-
+use any::AnyOwnExt;
 use borrow;
+use cast;
 use cleanup;
 use io::Writer;
-use libc::{c_char, size_t};
+use iter::{Iterator, Take};
 use local_data;
+use ops::Drop;
 use option::{Option, Some, None};
+use prelude::drop;
+use result::{Result, Ok, Err};
+use rt::Runtime;
 use rt::borrowck::BorrowRecord;
 use rt::borrowck;
-use rt::context::Context;
-use rt::env;
-use rt::kill::Death;
 use rt::local::Local;
+use rt::local_heap::LocalHeap;
 use rt::logging::StdErrLogger;
-use rt::sched::{Scheduler, SchedHandle};
-use rt::stack::{StackSegment, StackPool};
+use rt::rtio::LocalIo;
 use rt::unwind::Unwinder;
 use send_str::SendStr;
+use sync::arc::UnsafeArc;
+use sync::atomics::{AtomicUint, SeqCst, INIT_ATOMIC_UINT};
+use task::{TaskResult, TaskOpts};
 use unstable::finally::Finally;
-use unstable::mutex::Mutex;
+use unstable::mutex::{Mutex, MUTEX_INIT};
+
+#[cfg(stage0)]
+pub use rt::unwind::begin_unwind;
+
+// These two statics are used as bookeeping to keep track of the rust runtime's
+// count of threads. In 1:1 contexts, this is used to know when to return from
+// the main function, and in M:N contexts this is used to know when to shut down
+// the pool of schedulers.
+static mut TASK_COUNT: AtomicUint = INIT_ATOMIC_UINT;
+static mut TASK_LOCK: Mutex = MUTEX_INIT;
 
 // The Task struct represents all state associated with a rust
 // task. There are at this point two primary "subtypes" of task,
@@ -45,201 +57,90 @@ use unstable::mutex::Mutex;
 
 pub struct Task {
     heap: LocalHeap,
-    priv gc: GarbageCollector,
+    gc: GarbageCollector,
     storage: LocalStorage,
-    logger: Option<StdErrLogger>,
     unwinder: Unwinder,
     death: Death,
     destroyed: bool,
     name: Option<SendStr>,
-    coroutine: Option<Coroutine>,
-    sched: Option<~Scheduler>,
-    task_type: TaskType,
     // Dynamic borrowck debugging info
     borrow_list: Option<~[BorrowRecord]>,
+
+    logger: Option<StdErrLogger>,
     stdout_handle: Option<~Writer>,
 
-    // See the comments in the scheduler about why this is necessary
-    nasty_deschedule_lock: Mutex,
+    priv imp: Option<~Runtime>,
 }
 
-pub enum TaskType {
-    GreenTask(Option<SchedHome>),
-    SchedTask
-}
+pub struct GarbageCollector;
+pub struct LocalStorage(Option<local_data::Map>);
 
-/// A coroutine is nothing more than a (register context, stack) pair.
-pub struct Coroutine {
-    /// The segment of stack on which the task is currently running or
-    /// if the task is blocked, on which the task will resume
-    /// execution.
-    ///
-    /// Servo needs this to be public in order to tell SpiderMonkey
-    /// about the stack bounds.
-    current_stack_segment: StackSegment,
-    /// Always valid if the task is alive and not running.
-    saved_context: Context
+/// A handle to a blocked task. Usually this means having the ~Task pointer by
+/// ownership, but if the task is killable, a killer can steal it at any time.
+pub enum BlockedTask {
+    Owned(~Task),
+    Shared(UnsafeArc<AtomicUint>),
 }
 
-/// Some tasks have a dedicated home scheduler that they must run on.
-pub enum SchedHome {
-    AnySched,
-    Sched(SchedHandle)
+/// Per-task state related to task death, killing, failure, etc.
+pub struct Death {
+    // Action to be done with the exit code. If set, also makes the task wait
+    // until all its watched children exit before collecting the status.
+    on_exit: Option<proc(TaskResult)>,
 }
 
-pub struct GarbageCollector;
-pub struct LocalStorage(Option<local_data::Map>);
+pub struct BlockedTaskIterator {
+    priv inner: UnsafeArc<AtomicUint>,
+}
 
 impl Task {
-
-    // A helper to build a new task using the dynamically found
-    // scheduler and task. Only works in GreenTask context.
-    pub fn build_homed_child(stack_size: Option<uint>,
-                             f: proc(),
-                             home: SchedHome)
-                             -> ~Task {
-        let mut running_task = Local::borrow(None::<Task>);
-        let mut sched = running_task.get().sched.take_unwrap();
-        let new_task = ~running_task.get()
-                                    .new_child_homed(&mut sched.stack_pool,
-                                                     stack_size,
-                                                     home,
-                                                     f);
-        running_task.get().sched = Some(sched);
-        new_task
-    }
-
-    pub fn build_child(stack_size: Option<uint>, f: proc()) -> ~Task {
-        Task::build_homed_child(stack_size, f, AnySched)
-    }
-
-    pub fn build_homed_root(stack_size: Option<uint>,
-                            f: proc(),
-                            home: SchedHome)
-                            -> ~Task {
-        let mut running_task = Local::borrow(None::<Task>);
-        let mut sched = running_task.get().sched.take_unwrap();
-        let new_task = ~Task::new_root_homed(&mut sched.stack_pool,
-                                             stack_size,
-                                             home,
-                                             f);
-        running_task.get().sched = Some(sched);
-        new_task
-    }
-
-    pub fn build_root(stack_size: Option<uint>, f: proc()) -> ~Task {
-        Task::build_homed_root(stack_size, f, AnySched)
-    }
-
-    pub fn new_sched_task() -> Task {
+    pub fn new() -> Task {
         Task {
             heap: LocalHeap::new(),
             gc: GarbageCollector,
             storage: LocalStorage(None),
-            logger: None,
-            unwinder: Unwinder { unwinding: false, cause: None },
+            unwinder: Unwinder::new(),
             death: Death::new(),
             destroyed: false,
-            coroutine: Some(Coroutine::empty()),
             name: None,
-            sched: None,
-            task_type: SchedTask,
             borrow_list: None,
-            stdout_handle: None,
-            nasty_deschedule_lock: unsafe { Mutex::new() },
-        }
-    }
-
-    pub fn new_root(stack_pool: &mut StackPool,
-                    stack_size: Option<uint>,
-                    start: proc()) -> Task {
-        Task::new_root_homed(stack_pool, stack_size, AnySched, start)
-    }
-
-    pub fn new_child(&mut self,
-                     stack_pool: &mut StackPool,
-                     stack_size: Option<uint>,
-                     start: proc()) -> Task {
-        self.new_child_homed(stack_pool, stack_size, AnySched, start)
-    }
-
-    pub fn new_root_homed(stack_pool: &mut StackPool,
-                          stack_size: Option<uint>,
-                          home: SchedHome,
-                          start: proc()) -> Task {
-        Task {
-            heap: LocalHeap::new(),
-            gc: GarbageCollector,
-            storage: LocalStorage(None),
             logger: None,
-            unwinder: Unwinder { unwinding: false, cause: None },
-            death: Death::new(),
-            destroyed: false,
-            name: None,
-            coroutine: Some(Coroutine::new(stack_pool, stack_size, start)),
-            sched: None,
-            task_type: GreenTask(Some(home)),
-            borrow_list: None,
             stdout_handle: None,
-            nasty_deschedule_lock: unsafe { Mutex::new() },
+            imp: None,
         }
     }
 
-    pub fn new_child_homed(&mut self,
-                           stack_pool: &mut StackPool,
-                           stack_size: Option<uint>,
-                           home: SchedHome,
-                           start: proc()) -> Task {
-        Task {
-            heap: LocalHeap::new(),
-            gc: GarbageCollector,
-            storage: LocalStorage(None),
-            logger: None,
-            unwinder: Unwinder { unwinding: false, cause: None },
-            death: Death::new(),
-            destroyed: false,
-            name: None,
-            coroutine: Some(Coroutine::new(stack_pool, stack_size, start)),
-            sched: None,
-            task_type: GreenTask(Some(home)),
-            borrow_list: None,
-            stdout_handle: None,
-            nasty_deschedule_lock: unsafe { Mutex::new() },
-        }
-    }
-
-    pub fn give_home(&mut self, new_home: SchedHome) {
-        match self.task_type {
-            GreenTask(ref mut home) => {
-                *home = Some(new_home);
-            }
-            SchedTask => {
-                rtabort!("type error: used SchedTask as GreenTask");
-            }
-        }
-    }
-
-    pub fn take_unwrap_home(&mut self) -> SchedHome {
-        match self.task_type {
-            GreenTask(ref mut home) => {
-                let out = home.take_unwrap();
-                return out;
-            }
-            SchedTask => {
-                rtabort!("type error: used SchedTask as GreenTask");
-            }
-        }
-    }
-
-    pub fn run(&mut self, f: ||) {
-        rtdebug!("run called on task: {}", borrow::to_uint(self));
+    /// Executes the given closure as if it's running inside this task. The task
+    /// is consumed upon entry, and the destroyed task is returned from this
+    /// function in order for the caller to free. This function is guaranteed to
+    /// not unwind because the closure specified is run inside of a `rust_try`
+    /// block. (this is the only try/catch block in the world).
+    ///
+    /// This function is *not* meant to be abused as a "try/catch" block. This
+    /// is meant to be used at the absolute boundaries of a task's lifetime, and
+    /// only for that purpose.
+    pub fn run(~self, f: ||) -> ~Task {
+        // Need to put ourselves into TLS, but also need access to the unwinder.
+        // Unsafely get a handle to the task so we can continue to use it after
+        // putting it in tls (so we can invoke the unwinder).
+        let handle: *mut Task = unsafe {
+            *cast::transmute::<&~Task, &*mut Task>(&self)
+        };
+        Local::put(self);
+        unsafe { TASK_COUNT.fetch_add(1, SeqCst); }
 
         // The only try/catch block in the world. Attempt to run the task's
         // client-specified code and catch any failures.
-        self.unwinder.try(|| {
+        let try_block = || {
 
             // Run the task main function, then do some cleanup.
             f.finally(|| {
+                fn flush(w: Option<~Writer>) {
+                    match w {
+                        Some(mut w) => { w.flush(); }
+                        None => {}
+                    }
+                }
 
                 // First, destroy task-local storage. This may run user dtors.
                 //
@@ -260,7 +161,10 @@ impl Task {
                 // TLS, or possibly some destructors for those objects being
                 // annihilated invoke TLS. Sadly these two operations seemed to
                 // be intertwined, and miraculously work for now...
-                self.storage.take();
+                let mut task = Local::borrow(None::<Task>);
+                let storage = task.get().storage.take();
+                drop(task);
+                drop(storage);
 
                 // Destroy remaining boxes. Also may run user dtors.
                 unsafe { cleanup::annihilate(); }
@@ -268,77 +172,141 @@ impl Task {
                 // Finally flush and destroy any output handles which the task
                 // owns. There are no boxes here, and no user destructors should
                 // run after this any more.
-                match self.stdout_handle.take() {
-                    Some(handle) => {
-                        let mut handle = handle;
-                        handle.flush();
-                    }
-                    None => {}
-                }
-                self.logger.take();
+                let mut task = Local::borrow(None::<Task>);
+                let stdout = task.get().stdout_handle.take();
+                let logger = task.get().logger.take();
+                drop(task);
+
+                flush(stdout);
+                drop(logger);
             })
-        });
+        };
+
+        unsafe { (*handle).unwinder.try(try_block); }
 
         // Cleanup the dynamic borrowck debugging info
         borrowck::clear_task_borrow_list();
 
-        self.death.collect_failure(self.unwinder.result());
-        self.destroyed = true;
+        // Here we must unsafely borrow the task in order to not remove it from
+        // TLS. When collecting failure, we may attempt to send on a channel (or
+        // just run aribitrary code), so we must be sure to still have a local
+        // task in TLS.
+        unsafe {
+            let me: *mut Task = Local::unsafe_borrow();
+            (*me).death.collect_failure((*me).unwinder.result());
+
+            // see comments on these statics for why they're used
+            if TASK_COUNT.fetch_sub(1, SeqCst) == 1 {
+                TASK_LOCK.lock();
+                TASK_LOCK.signal();
+                TASK_LOCK.unlock();
+            }
+        }
+        let mut me: ~Task = Local::take();
+        me.destroyed = true;
+        return me;
     }
 
-    // New utility functions for homes.
+    /// Inserts a runtime object into this task, transferring ownership to the
+    /// task. It is illegal to replace a previous runtime object in this task
+    /// with this argument.
+    pub fn put_runtime(&mut self, ops: ~Runtime) {
+        assert!(self.imp.is_none());
+        self.imp = Some(ops);
+    }
 
-    pub fn is_home_no_tls(&self, sched: &~Scheduler) -> bool {
-        match self.task_type {
-            GreenTask(Some(AnySched)) => { false }
-            GreenTask(Some(Sched(SchedHandle { sched_id: ref id, .. }))) => {
-                *id == sched.sched_id()
-            }
-            GreenTask(None) => {
-                rtabort!("task without home");
-            }
-            SchedTask => {
-                // Awe yea
-                rtabort!("type error: expected: GreenTask, found: SchedTask");
+    /// Attempts to extract the runtime as a specific type. If the runtime does
+    /// not have the provided type, then the runtime is not removed. If the
+    /// runtime does have the specified type, then it is removed and returned
+    /// (transfer of ownership).
+    ///
+    /// It is recommended to only use this method when *absolutely necessary*.
+    /// This function may not be available in the future.
+    pub fn maybe_take_runtime<T: 'static>(&mut self) -> Option<~T> {
+        // This is a terrible, terrible function. The general idea here is to
+        // take the runtime, cast it to ~Any, check if it has the right type,
+        // and then re-cast it back if necessary. The method of doing this is
+        // pretty sketchy and involves shuffling vtables of trait objects
+        // around, but it gets the job done.
+        //
+        // XXX: This function is a serious code smell and should be avoided at
+        //      all costs. I have yet to think of a method to avoid this
+        //      function, and I would be saddened if more usage of the function
+        //      crops up.
+        unsafe {
+            let imp = self.imp.take_unwrap();
+            let &(vtable, _): &(uint, uint) = cast::transmute(&imp);
+            match imp.wrap().move::<T>() {
+                Ok(t) => Some(t),
+                Err(t) => {
+                    let (_, obj): (uint, uint) = cast::transmute(t);
+                    let obj: ~Runtime = cast::transmute((vtable, obj));
+                    self.put_runtime(obj);
+                    None
+                }
             }
         }
     }
 
-    pub fn homed(&self) -> bool {
-        match self.task_type {
-            GreenTask(Some(AnySched)) => { false }
-            GreenTask(Some(Sched(SchedHandle { .. }))) => { true }
-            GreenTask(None) => {
-                rtabort!("task without home");
-            }
-            SchedTask => {
-                rtabort!("type error: expected: GreenTask, found: SchedTask");
-            }
-        }
+    /// Spawns a sibling to this task. The newly spawned task is configured with
+    /// the `opts` structure and will run `f` as the body of its code.
+    pub fn spawn_sibling(mut ~self, opts: TaskOpts, f: proc()) {
+        let ops = self.imp.take_unwrap();
+        ops.spawn_sibling(self, opts, f)
     }
 
-    // Grab both the scheduler and the task from TLS and check if the
-    // task is executing on an appropriate scheduler.
-    pub fn on_appropriate_sched() -> bool {
-        let mut task = Local::borrow(None::<Task>);
-        let sched_id = task.get().sched.get_ref().sched_id();
-        let sched_run_anything = task.get().sched.get_ref().run_anything;
-        match task.get().task_type {
-            GreenTask(Some(AnySched)) => {
-                rtdebug!("anysched task in sched check ****");
-                sched_run_anything
-            }
-            GreenTask(Some(Sched(SchedHandle { sched_id: ref id, ..}))) => {
-                rtdebug!("homed task in sched check ****");
-                *id == sched_id
-            }
-            GreenTask(None) => {
-                rtabort!("task without home");
-            }
-            SchedTask => {
-                rtabort!("type error: expected: GreenTask, found: SchedTask");
-            }
+    /// Deschedules the current task, invoking `f` `amt` times. It is not
+    /// recommended to use this function directly, but rather communication
+    /// primitives in `std::comm` should be used.
+    pub fn deschedule(mut ~self, amt: uint,
+                      f: |BlockedTask| -> Result<(), BlockedTask>) {
+        let ops = self.imp.take_unwrap();
+        ops.deschedule(amt, self, f)
+    }
+
+    /// Wakes up a previously blocked task, optionally specifiying whether the
+    /// current task can accept a change in scheduling. This function can only
+    /// be called on tasks that were previously blocked in `deschedule`.
+    pub fn reawaken(mut ~self, can_resched: bool) {
+        let ops = self.imp.take_unwrap();
+        ops.reawaken(self, can_resched);
+    }
+
+    /// Yields control of this task to another task. This function will
+    /// eventually return, but possibly not immediately. This is used as an
+    /// opportunity to allow other tasks a chance to run.
+    pub fn yield_now(mut ~self) {
+        let ops = self.imp.take_unwrap();
+        ops.yield_now(self);
+    }
+
+    /// Similar to `yield_now`, except that this function may immediately return
+    /// without yielding (depending on what the runtime decides to do).
+    pub fn maybe_yield(mut ~self) {
+        let ops = self.imp.take_unwrap();
+        ops.maybe_yield(self);
+    }
+
+    /// Acquires a handle to the I/O factory that this task contains, normally
+    /// stored in the task's runtime. This factory may not always be available,
+    /// which is why the return type is `Option`
+    pub fn local_io<'a>(&'a mut self) -> Option<LocalIo<'a>> {
+        self.imp.get_mut_ref().local_io()
+    }
+
+    /// The main function of all rust executables will by default use this
+    /// function. This function will *block* the OS thread (hence the `unsafe`)
+    /// waiting for all known tasks to complete. Once this function has
+    /// returned, it is guaranteed that no more user-defined code is still
+    /// running.
+    pub unsafe fn wait_for_other_tasks(&mut self) {
+        TASK_COUNT.fetch_sub(1, SeqCst); // don't count ourselves
+        TASK_LOCK.lock();
+        while TASK_COUNT.load(SeqCst) > 0 {
+            TASK_LOCK.wait();
         }
+        TASK_LOCK.unlock();
+        TASK_COUNT.fetch_add(1, SeqCst); // add ourselves back in
     }
 }
 
@@ -346,348 +314,192 @@ impl Drop for Task {
     fn drop(&mut self) {
         rtdebug!("called drop for a task: {}", borrow::to_uint(self));
         rtassert!(self.destroyed);
-
-        unsafe { self.nasty_deschedule_lock.destroy(); }
     }
 }
 
-// Coroutines represent nothing more than a context and a stack
-// segment.
-
-impl Coroutine {
-
-    pub fn new(stack_pool: &mut StackPool,
-               stack_size: Option<uint>,
-               start: proc())
-               -> Coroutine {
-        let stack_size = match stack_size {
-            Some(size) => size,
-            None => env::min_stack()
-        };
-        let start = Coroutine::build_start_wrapper(start);
-        let mut stack = stack_pool.take_segment(stack_size);
-        let initial_context = Context::new(start, &mut stack);
-        Coroutine {
-            current_stack_segment: stack,
-            saved_context: initial_context
-        }
+impl Iterator<BlockedTask> for BlockedTaskIterator {
+    fn next(&mut self) -> Option<BlockedTask> {
+        Some(Shared(self.inner.clone()))
     }
+}
 
-    pub fn empty() -> Coroutine {
-        Coroutine {
-            current_stack_segment: StackSegment::new(0),
-            saved_context: Context::empty()
+impl BlockedTask {
+    /// Returns Some if the task was successfully woken; None if already killed.
+    pub fn wake(self) -> Option<~Task> {
+        match self {
+            Owned(task) => Some(task),
+            Shared(arc) => unsafe {
+                match (*arc.get()).swap(0, SeqCst) {
+                    0 => None,
+                    n => Some(cast::transmute(n)),
+                }
+            }
         }
     }
 
-    fn build_start_wrapper(start: proc()) -> proc() {
-        let wrapper: proc() = proc() {
-            // First code after swap to this new context. Run our
-            // cleanup job.
-            unsafe {
+    // This assertion has two flavours because the wake involves an atomic op.
+    // In the faster version, destructors will fail dramatically instead.
+    #[cfg(not(test))] pub fn trash(self) { }
+    #[cfg(test)]      pub fn trash(self) { assert!(self.wake().is_none()); }
 
-                // Again - might work while safe, or it might not.
-                {
-                    let mut sched = Local::borrow(None::<Scheduler>);
-                    sched.get().run_cleanup_job();
-                }
+    /// Create a blocked task, unless the task was already killed.
+    pub fn block(task: ~Task) -> BlockedTask {
+        Owned(task)
+    }
 
-                // To call the run method on a task we need a direct
-                // reference to it. The task is in TLS, so we can
-                // simply unsafe_borrow it to get this reference. We
-                // need to still have the task in TLS though, so we
-                // need to unsafe_borrow.
-                let task: *mut Task = Local::unsafe_borrow();
-
-                let mut start_cell = Some(start);
-                (*task).run(|| {
-                    // N.B. Removing `start` from the start wrapper
-                    // closure by emptying a cell is critical for
-                    // correctness. The ~Task pointer, and in turn the
-                    // closure used to initialize the first call
-                    // frame, is destroyed in the scheduler context,
-                    // not task context. So any captured closures must
-                    // not contain user-definable dtors that expect to
-                    // be in task context. By moving `start` out of
-                    // the closure, all the user code goes our of
-                    // scope while the task is still running.
-                    let start = start_cell.take_unwrap();
-                    start();
-                });
+    /// Converts one blocked task handle to a list of many handles to the same.
+    pub fn make_selectable(self, num_handles: uint) -> Take<BlockedTaskIterator>
+    {
+        let arc = match self {
+            Owned(task) => {
+                let flag = unsafe { AtomicUint::new(cast::transmute(task)) };
+                UnsafeArc::new(flag)
             }
-
-            // We remove the sched from the Task in TLS right now.
-            let sched: ~Scheduler = Local::take();
-            // ... allowing us to give it away when performing a
-            // scheduling operation.
-            sched.terminate_current_task()
+            Shared(arc) => arc.clone(),
         };
-        return wrapper;
+        BlockedTaskIterator{ inner: arc }.take(num_handles)
     }
 
-    /// Destroy coroutine and try to reuse stack segment.
-    pub fn recycle(self, stack_pool: &mut StackPool) {
+    /// Convert to an unsafe uint value. Useful for storing in a pipe's state
+    /// flag.
+    #[inline]
+    pub unsafe fn cast_to_uint(self) -> uint {
         match self {
-            Coroutine { current_stack_segment, .. } => {
-                stack_pool.give_segment(current_stack_segment);
+            Owned(task) => {
+                let blocked_task_ptr: uint = cast::transmute(task);
+                rtassert!(blocked_task_ptr & 0x1 == 0);
+                blocked_task_ptr
+            }
+            Shared(arc) => {
+                let blocked_task_ptr: uint = cast::transmute(~arc);
+                rtassert!(blocked_task_ptr & 0x1 == 0);
+                blocked_task_ptr | 0x1
             }
         }
     }
 
-}
-
-/// This function is invoked from rust's current __morestack function. Segmented
-/// stacks are currently not enabled as segmented stacks, but rather one giant
-/// stack segment. This means that whenever we run out of stack, we want to
-/// truly consider it to be stack overflow rather than allocating a new stack.
-#[no_mangle]      // - this is called from C code
-#[no_split_stack] // - it would be sad for this function to trigger __morestack
-#[doc(hidden)]    // - Function must be `pub` to get exported, but it's
-                  //   irrelevant for documentation purposes.
-#[cfg(not(test))] // in testing, use the original libstd's version
-pub extern "C" fn rust_stack_exhausted() {
-    use rt::context;
-    use rt::in_green_task_context;
-    use rt::task::Task;
-    use rt::local::Local;
-    use unstable::intrinsics;
-
-    unsafe {
-        // We're calling this function because the stack just ran out. We need
-        // to call some other rust functions, but if we invoke the functions
-        // right now it'll just trigger this handler being called again. In
-        // order to alleviate this, we move the stack limit to be inside of the
-        // red zone that was allocated for exactly this reason.
-        let limit = context::get_sp_limit();
-        context::record_sp_limit(limit - context::RED_ZONE / 2);
-
-        // This probably isn't the best course of action. Ideally one would want
-        // to unwind the stack here instead of just aborting the entire process.
-        // This is a tricky problem, however. There's a few things which need to
-        // be considered:
-        //
-        //  1. We're here because of a stack overflow, yet unwinding will run
-        //     destructors and hence arbitrary code. What if that code overflows
-        //     the stack? One possibility is to use the above allocation of an
-        //     extra 10k to hope that we don't hit the limit, and if we do then
-        //     abort the whole program. Not the best, but kind of hard to deal
-        //     with unless we want to switch stacks.
-        //
-        //  2. LLVM will optimize functions based on whether they can unwind or
-        //     not. It will flag functions with 'nounwind' if it believes that
-        //     the function cannot trigger unwinding, but if we do unwind on
-        //     stack overflow then it means that we could unwind in any function
-        //     anywhere. We would have to make sure that LLVM only places the
-        //     nounwind flag on functions which don't call any other functions.
-        //
-        //  3. The function that overflowed may have owned arguments. These
-        //     arguments need to have their destructors run, but we haven't even
-        //     begun executing the function yet, so unwinding will not run the
-        //     any landing pads for these functions. If this is ignored, then
-        //     the arguments will just be leaked.
-        //
-        // Exactly what to do here is a very delicate topic, and is possibly
-        // still up in the air for what exactly to do. Some relevant issues:
-        //
-        //  #3555 - out-of-stack failure leaks arguments
-        //  #3695 - should there be a stack limit?
-        //  #9855 - possible strategies which could be taken
-        //  #9854 - unwinding on windows through __morestack has never worked
-        //  #2361 - possible implementation of not using landing pads
-
-        if in_green_task_context() {
-            let mut task = Local::borrow(None::<Task>);
-            let n = task.get()
-                        .name
-                        .as_ref()
-                        .map(|n| n.as_slice())
-                        .unwrap_or("<unnamed>");
-
-            // See the message below for why this is not emitted to the
-            // task's logger. This has the additional conundrum of the
-            // logger may not be initialized just yet, meaning that an FFI
-            // call would happen to initialized it (calling out to libuv),
-            // and the FFI call needs 2MB of stack when we just ran out.
-            rterrln!("task '{}' has overflowed its stack", n);
+    /// Convert from an unsafe uint value. Useful for retrieving a pipe's state
+    /// flag.
+    #[inline]
+    pub unsafe fn cast_from_uint(blocked_task_ptr: uint) -> BlockedTask {
+        if blocked_task_ptr & 0x1 == 0 {
+            Owned(cast::transmute(blocked_task_ptr))
         } else {
-            rterrln!("stack overflow in non-task context");
+            let ptr: ~UnsafeArc<AtomicUint> =
+                cast::transmute(blocked_task_ptr & !1);
+            Shared(*ptr)
         }
-
-        intrinsics::abort();
     }
 }
 
-/// This is the entry point of unwinding for things like lang items and such.
-/// The arguments are normally generated by the compiler, and need to
-/// have static lifetimes.
-pub fn begin_unwind_raw(msg: *c_char, file: *c_char, line: size_t) -> ! {
-    use c_str::CString;
-    use cast::transmute;
+impl Death {
+    pub fn new() -> Death {
+        Death { on_exit: None, }
+    }
 
-    #[inline]
-    fn static_char_ptr(p: *c_char) -> &'static str {
-        let s = unsafe { CString::new(p, false) };
-        match s.as_str() {
-            Some(s) => unsafe { transmute::<&str, &'static str>(s) },
-            None => rtabort!("message wasn't utf8?")
+    /// Collect failure exit codes from children and propagate them to a parent.
+    pub fn collect_failure(&mut self, result: TaskResult) {
+        match self.on_exit.take() {
+            Some(f) => f(result),
+            None => {}
         }
     }
-
-    let msg = static_char_ptr(msg);
-    let file = static_char_ptr(file);
-
-    begin_unwind(msg, file, line as uint)
 }
 
-/// This is the entry point of unwinding for fail!() and assert!().
-pub fn begin_unwind<M: Any + Send>(msg: M, file: &'static str, line: uint) -> ! {
-    use any::AnyRefExt;
-    use rt::in_green_task_context;
-    use rt::local::Local;
-    use rt::task::Task;
-    use str::Str;
-    use unstable::intrinsics;
-
-    unsafe {
-        let task: *mut Task;
-        // Note that this should be the only allocation performed in this block.
-        // Currently this means that fail!() on OOM will invoke this code path,
-        // but then again we're not really ready for failing on OOM anyway. If
-        // we do start doing this, then we should propagate this allocation to
-        // be performed in the parent of this task instead of the task that's
-        // failing.
-        let msg = ~msg as ~Any;
-
-        {
-            //let msg: &Any = msg;
-            let msg_s = match msg.as_ref::<&'static str>() {
-                Some(s) => *s,
-                None => match msg.as_ref::<~str>() {
-                    Some(s) => s.as_slice(),
-                    None => "~Any",
-                }
-            };
-
-            if !in_green_task_context() {
-                rterrln!("failed in non-task context at '{}', {}:{}",
-                         msg_s, file, line);
-                intrinsics::abort();
-            }
-
-            task = Local::unsafe_borrow();
-            let n = (*task).name.as_ref().map(|n| n.as_slice()).unwrap_or("<unnamed>");
-
-            // XXX: this should no get forcibly printed to the console, this should
-            //      either be sent to the parent task (ideally), or get printed to
-            //      the task's logger. Right now the logger is actually a uvio
-            //      instance, which uses unkillable blocks internally for various
-            //      reasons. This will cause serious trouble if the task is failing
-            //      due to mismanagment of its own kill flag, so calling our own
-            //      logger in its current state is a bit of a problem.
-
-            rterrln!("task '{}' failed at '{}', {}:{}", n, msg_s, file, line);
-
-            if (*task).unwinder.unwinding {
-                rtabort!("unwinding again");
-            }
-        }
-
-        (*task).unwinder.begin_unwind(msg);
+impl Drop for Death {
+    fn drop(&mut self) {
+        // make this type noncopyable
     }
 }
 
 #[cfg(test)]
 mod test {
     use super::*;
-    use rt::test::*;
     use prelude::*;
+    use task;
 
     #[test]
     fn local_heap() {
-        do run_in_newsched_task() {
-            let a = @5;
-            let b = a;
-            assert!(*a == 5);
-            assert!(*b == 5);
-        }
+        let a = @5;
+        let b = a;
+        assert!(*a == 5);
+        assert!(*b == 5);
     }
 
     #[test]
     fn tls() {
         use local_data;
-        do run_in_newsched_task() {
-            local_data_key!(key: @~str)
-            local_data::set(key, @~"data");
-            assert!(*local_data::get(key, |k| k.map(|k| *k)).unwrap() == ~"data");
-            local_data_key!(key2: @~str)
-            local_data::set(key2, @~"data");
-            assert!(*local_data::get(key2, |k| k.map(|k| *k)).unwrap() == ~"data");
-        }
+        local_data_key!(key: @~str)
+        local_data::set(key, @~"data");
+        assert!(*local_data::get(key, |k| k.map(|k| *k)).unwrap() == ~"data");
+        local_data_key!(key2: @~str)
+        local_data::set(key2, @~"data");
+        assert!(*local_data::get(key2, |k| k.map(|k| *k)).unwrap() == ~"data");
     }
 
     #[test]
     fn unwind() {
-        do run_in_newsched_task() {
-            let result = spawntask_try(proc()());
-            rtdebug!("trying first assert");
-            assert!(result.is_ok());
-            let result = spawntask_try(proc() fail!());
-            rtdebug!("trying second assert");
-            assert!(result.is_err());
-        }
+        let result = task::try(proc()());
+        rtdebug!("trying first assert");
+        assert!(result.is_ok());
+        let result = task::try::<()>(proc() fail!());
+        rtdebug!("trying second assert");
+        assert!(result.is_err());
     }
 
     #[test]
     fn rng() {
-        do run_in_uv_task() {
-            use rand::{rng, Rng};
-            let mut r = rng();
-            let _ = r.next_u32();
-        }
+        use rand::{rng, Rng};
+        let mut r = rng();
+        let _ = r.next_u32();
     }
 
     #[test]
     fn logging() {
-        do run_in_uv_task() {
-            info!("here i am. logging in a newsched task");
-        }
+        info!("here i am. logging in a newsched task");
     }
 
     #[test]
     fn comm_stream() {
-        do run_in_newsched_task() {
-            let (port, chan) = Chan::new();
-            chan.send(10);
-            assert!(port.recv() == 10);
-        }
+        let (port, chan) = Chan::new();
+        chan.send(10);
+        assert!(port.recv() == 10);
     }
 
     #[test]
     fn comm_shared_chan() {
-        do run_in_newsched_task() {
-            let (port, chan) = SharedChan::new();
-            chan.send(10);
-            assert!(port.recv() == 10);
-        }
+        let (port, chan) = SharedChan::new();
+        chan.send(10);
+        assert!(port.recv() == 10);
     }
 
     #[test]
     fn heap_cycles() {
         use option::{Option, Some, None};
 
-        do run_in_newsched_task {
-            struct List {
-                next: Option<@mut List>,
-            }
+        struct List {
+            next: Option<@mut List>,
+        }
 
-            let a = @mut List { next: None };
-            let b = @mut List { next: Some(a) };
+        let a = @mut List { next: None };
+        let b = @mut List { next: Some(a) };
 
-            a.next = Some(b);
-        }
+        a.next = Some(b);
     }
 
     #[test]
     #[should_fail]
-    fn test_begin_unwind() { begin_unwind("cause", file!(), line!()) }
+    fn test_begin_unwind() {
+        use rt::unwind::begin_unwind;
+        begin_unwind("cause", file!(), line!())
+    }
+
+    // Task blocking tests
+
+    #[test]
+    fn block_and_wake() {
+        let task = ~Task::new();
+        let mut task = BlockedTask::block(task).wake().unwrap();
+        task.destroyed = true;
+    }
 }
diff --git a/src/libstd/rt/test.rs b/src/libstd/rt/test.rs
deleted file mode 100644
index 2b48b396c99..00000000000
--- a/src/libstd/rt/test.rs
+++ /dev/null
@@ -1,440 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-use io::net::ip::{SocketAddr, Ipv4Addr, Ipv6Addr};
-
-use clone::Clone;
-use container::Container;
-use iter::{Iterator, range};
-use option::{Some, None};
-use os;
-use path::GenericPath;
-use path::Path;
-use rand::Rng;
-use rand;
-use result::{Result, Ok, Err};
-use rt::basic;
-use rt::deque::BufferPool;
-use comm::Chan;
-use rt::new_event_loop;
-use rt::sched::Scheduler;
-use rt::sleeper_list::SleeperList;
-use rt::task::Task;
-use rt::thread::Thread;
-use task::TaskResult;
-use unstable::{run_in_bare_thread};
-use vec;
-use vec::{OwnedVector, MutableVector, ImmutableVector};
-
-pub fn new_test_uv_sched() -> Scheduler {
-
-    let mut pool = BufferPool::new();
-    let (worker, stealer) = pool.deque();
-
-    let mut sched = Scheduler::new(new_event_loop(),
-                                   worker,
-                                   ~[stealer],
-                                   SleeperList::new());
-
-    // Don't wait for the Shutdown message
-    sched.no_sleep = true;
-    return sched;
-
-}
-
-pub fn new_test_sched() -> Scheduler {
-    let mut pool = BufferPool::new();
-    let (worker, stealer) = pool.deque();
-
-    let mut sched = Scheduler::new(basic::event_loop(),
-                                   worker,
-                                   ~[stealer],
-                                   SleeperList::new());
-
-    // Don't wait for the Shutdown message
-    sched.no_sleep = true;
-    return sched;
-}
-
-pub fn run_in_uv_task(f: proc()) {
-    do run_in_bare_thread {
-        run_in_uv_task_core(f);
-    }
-}
-
-pub fn run_in_newsched_task(f: proc()) {
-    do run_in_bare_thread {
-        run_in_newsched_task_core(f);
-    }
-}
-
-pub fn run_in_uv_task_core(f: proc()) {
-
-    use rt::sched::Shutdown;
-
-    let mut sched = ~new_test_uv_sched();
-    let exit_handle = sched.make_handle();
-
-    let on_exit: proc(TaskResult) = proc(exit_status: TaskResult) {
-        let mut exit_handle = exit_handle;
-        exit_handle.send(Shutdown);
-        rtassert!(exit_status.is_ok());
-    };
-    let mut task = ~Task::new_root(&mut sched.stack_pool, None, f);
-    task.death.on_exit = Some(on_exit);
-
-    sched.bootstrap(task);
-}
-
-pub fn run_in_newsched_task_core(f: proc()) {
-    use rt::sched::Shutdown;
-
-    let mut sched = ~new_test_sched();
-    let exit_handle = sched.make_handle();
-
-    let on_exit: proc(TaskResult) = proc(exit_status: TaskResult) {
-        let mut exit_handle = exit_handle;
-        exit_handle.send(Shutdown);
-        rtassert!(exit_status.is_ok());
-    };
-    let mut task = ~Task::new_root(&mut sched.stack_pool, None, f);
-    task.death.on_exit = Some(on_exit);
-
-    sched.bootstrap(task);
-}
-
-#[cfg(target_os="macos")]
-#[allow(non_camel_case_types)]
-mod darwin_fd_limit {
-    /*!
-     * darwin_fd_limit exists to work around an issue where launchctl on Mac OS X defaults the
-     * rlimit maxfiles to 256/unlimited. The default soft limit of 256 ends up being far too low
-     * for our multithreaded scheduler testing, depending on the number of cores available.
-     *
-     * This fixes issue #7772.
-     */
-
-    use libc;
-    type rlim_t = libc::uint64_t;
-    struct rlimit {
-        rlim_cur: rlim_t,
-        rlim_max: rlim_t
-    }
-    #[nolink]
-    extern {
-        // name probably doesn't need to be mut, but the C function doesn't specify const
-        fn sysctl(name: *mut libc::c_int, namelen: libc::c_uint,
-                  oldp: *mut libc::c_void, oldlenp: *mut libc::size_t,
-                  newp: *mut libc::c_void, newlen: libc::size_t) -> libc::c_int;
-        fn getrlimit(resource: libc::c_int, rlp: *mut rlimit) -> libc::c_int;
-        fn setrlimit(resource: libc::c_int, rlp: *rlimit) -> libc::c_int;
-    }
-    static CTL_KERN: libc::c_int = 1;
-    static KERN_MAXFILESPERPROC: libc::c_int = 29;
-    static RLIMIT_NOFILE: libc::c_int = 8;
-
-    pub unsafe fn raise_fd_limit() {
-        // The strategy here is to fetch the current resource limits, read the kern.maxfilesperproc
-        // sysctl value, and bump the soft resource limit for maxfiles up to the sysctl value.
-        use ptr::{to_unsafe_ptr, to_mut_unsafe_ptr, mut_null};
-        use mem::size_of_val;
-        use os::last_os_error;
-
-        // Fetch the kern.maxfilesperproc value
-        let mut mib: [libc::c_int, ..2] = [CTL_KERN, KERN_MAXFILESPERPROC];
-        let mut maxfiles: libc::c_int = 0;
-        let mut size: libc::size_t = size_of_val(&maxfiles) as libc::size_t;
-        if sysctl(to_mut_unsafe_ptr(&mut mib[0]), 2,
-                  to_mut_unsafe_ptr(&mut maxfiles) as *mut libc::c_void,
-                  to_mut_unsafe_ptr(&mut size),
-                  mut_null(), 0) != 0 {
-            let err = last_os_error();
-            error!("raise_fd_limit: error calling sysctl: {}", err);
-            return;
-        }
-
-        // Fetch the current resource limits
-        let mut rlim = rlimit{rlim_cur: 0, rlim_max: 0};
-        if getrlimit(RLIMIT_NOFILE, to_mut_unsafe_ptr(&mut rlim)) != 0 {
-            let err = last_os_error();
-            error!("raise_fd_limit: error calling getrlimit: {}", err);
-            return;
-        }
-
-        // Bump the soft limit to the smaller of kern.maxfilesperproc and the hard limit
-        rlim.rlim_cur = ::cmp::min(maxfiles as rlim_t, rlim.rlim_max);
-
-        // Set our newly-increased resource limit
-        if setrlimit(RLIMIT_NOFILE, to_unsafe_ptr(&rlim)) != 0 {
-            let err = last_os_error();
-            error!("raise_fd_limit: error calling setrlimit: {}", err);
-            return;
-        }
-    }
-}
-
-#[cfg(not(target_os="macos"))]
-mod darwin_fd_limit {
-    pub unsafe fn raise_fd_limit() {}
-}
-
-#[doc(hidden)]
-pub fn prepare_for_lots_of_tests() {
-    // Bump the fd limit on OS X. See darwin_fd_limit for an explanation.
-    unsafe { darwin_fd_limit::raise_fd_limit() }
-}
-
-/// Create more than one scheduler and run a function in a task
-/// in one of the schedulers. The schedulers will stay alive
-/// until the function `f` returns.
-pub fn run_in_mt_newsched_task(f: proc()) {
-    use os;
-    use from_str::FromStr;
-    use rt::sched::Shutdown;
-    use rt::util;
-
-    // see comment in other function (raising fd limits)
-    prepare_for_lots_of_tests();
-
-    do run_in_bare_thread {
-        let nthreads = match os::getenv("RUST_RT_TEST_THREADS") {
-            Some(nstr) => FromStr::from_str(nstr).unwrap(),
-            None => {
-                if util::limit_thread_creation_due_to_osx_and_valgrind() {
-                    1
-                } else {
-                    // Using more threads than cores in test code
-                    // to force the OS to preempt them frequently.
-                    // Assuming that this help stress test concurrent types.
-                    util::num_cpus() * 2
-                }
-            }
-        };
-
-        let sleepers = SleeperList::new();
-
-        let mut handles = ~[];
-        let mut scheds = ~[];
-
-        let mut pool = BufferPool::<~Task>::new();
-        let workers = range(0, nthreads).map(|_| pool.deque());
-        let (workers, stealers) = vec::unzip(workers);
-
-        for worker in workers.move_iter() {
-            let loop_ = new_event_loop();
-            let mut sched = ~Scheduler::new(loop_,
-                                            worker,
-                                            stealers.clone(),
-                                            sleepers.clone());
-            let handle = sched.make_handle();
-
-            handles.push(handle);
-            scheds.push(sched);
-        }
-
-        let handles = handles;  // Work around not being able to capture mut
-        let on_exit: proc(TaskResult) = proc(exit_status: TaskResult) {
-            // Tell schedulers to exit
-            let mut handles = handles;
-            for handle in handles.mut_iter() {
-                handle.send(Shutdown);
-            }
-
-            rtassert!(exit_status.is_ok());
-        };
-        let mut main_task = ~Task::new_root(&mut scheds[0].stack_pool,
-                                            None,
-                                            f);
-        main_task.death.on_exit = Some(on_exit);
-
-        let mut threads = ~[];
-
-        let main_thread = {
-            let sched = scheds.pop();
-            let main_task = main_task;
-            do Thread::start {
-                sched.bootstrap(main_task);
-            }
-        };
-        threads.push(main_thread);
-
-        while !scheds.is_empty() {
-            let mut sched = scheds.pop();
-            let bootstrap_task = ~do Task::new_root(&mut sched.stack_pool, None) || {
-                rtdebug!("bootstrapping non-primary scheduler");
-            };
-            let sched = sched;
-            let thread = do Thread::start {
-                sched.bootstrap(bootstrap_task);
-            };
-
-            threads.push(thread);
-        }
-
-        // Wait for schedulers
-        for thread in threads.move_iter() {
-            thread.join();
-        }
-    }
-
-}
-
-/// Test tasks will abort on failure instead of unwinding
-pub fn spawntask(f: proc()) {
-    Scheduler::run_task(Task::build_child(None, f));
-}
-
-/// Create a new task and run it right now. Aborts on failure
-pub fn spawntask_later(f: proc()) {
-    Scheduler::run_task_later(Task::build_child(None, f));
-}
-
-pub fn spawntask_random(f: proc()) {
-    use rand::{Rand, rng};
-
-    let mut rng = rng();
-    let run_now: bool = Rand::rand(&mut rng);
-
-    if run_now {
-        spawntask(f)
-    } else {
-        spawntask_later(f)
-    }
-}
-
-pub fn spawntask_try(f: proc()) -> Result<(),()> {
-
-    let (port, chan) = Chan::new();
-    let on_exit: proc(TaskResult) = proc(exit_status) {
-        chan.send(exit_status)
-    };
-
-    let mut new_task = Task::build_root(None, f);
-    new_task.death.on_exit = Some(on_exit);
-
-    Scheduler::run_task(new_task);
-
-    let exit_status = port.recv();
-    if exit_status.is_ok() { Ok(()) } else { Err(()) }
-
-}
-
-/// Spawn a new task in a new scheduler and return a thread handle.
-pub fn spawntask_thread(f: proc()) -> Thread<()> {
-    let thread = do Thread::start {
-        run_in_newsched_task_core(f);
-    };
-
-    return thread;
-}
-
-/// Get a ~Task for testing purposes other than actually scheduling it.
-pub fn with_test_task(blk: proc(~Task) -> ~Task) {
-    do run_in_bare_thread {
-        let mut sched = ~new_test_sched();
-        let task = blk(~Task::new_root(&mut sched.stack_pool,
-                                       None,
-                                       proc() {}));
-        cleanup_task(task);
-    }
-}
-
-/// Use to cleanup tasks created for testing but not "run".
-pub fn cleanup_task(mut task: ~Task) {
-    task.destroyed = true;
-}
-
-/// Get a port number, starting at 9600, for use in tests
-pub fn next_test_port() -> u16 {
-    use unstable::mutex::{Mutex, MUTEX_INIT};
-    static mut lock: Mutex = MUTEX_INIT;
-    static mut next_offset: u16 = 0;
-    unsafe {
-        let base = base_port();
-        lock.lock();
-        let ret = base + next_offset;
-        next_offset += 1;
-        lock.unlock();
-        return ret;
-    }
-}
-
-/// Get a temporary path which could be the location of a unix socket
-pub fn next_test_unix() -> Path {
-    if cfg!(unix) {
-        os::tmpdir().join(rand::task_rng().gen_ascii_str(20))
-    } else {
-        Path::new(r"\\.\pipe\" + rand::task_rng().gen_ascii_str(20))
-    }
-}
-
-/// Get a unique IPv4 localhost:port pair starting at 9600
-pub fn next_test_ip4() -> SocketAddr {
-    SocketAddr { ip: Ipv4Addr(127, 0, 0, 1), port: next_test_port() }
-}
-
-/// Get a unique IPv6 localhost:port pair starting at 9600
-pub fn next_test_ip6() -> SocketAddr {
-    SocketAddr { ip: Ipv6Addr(0, 0, 0, 0, 0, 0, 0, 1), port: next_test_port() }
-}
-
-/*
-XXX: Welcome to MegaHack City.
-
-The bots run multiple builds at the same time, and these builds
-all want to use ports. This function figures out which workspace
-it is running in and assigns a port range based on it.
-*/
-fn base_port() -> u16 {
-    use os;
-    use str::StrSlice;
-    use vec::ImmutableVector;
-
-    let base = 9600u16;
-    let range = 1000u16;
-
-    let bases = [
-        ("32-opt", base + range * 1),
-        ("32-noopt", base + range * 2),
-        ("64-opt", base + range * 3),
-        ("64-noopt", base + range * 4),
-        ("64-opt-vg", base + range * 5),
-        ("all-opt", base + range * 6),
-        ("snap3", base + range * 7),
-        ("dist", base + range * 8)
-    ];
-
-    // FIXME (#9639): This needs to handle non-utf8 paths
-    let path = os::getcwd();
-    let path_s = path.as_str().unwrap();
-
-    let mut final_base = base;
-
-    for &(dir, base) in bases.iter() {
-        if path_s.contains(dir) {
-            final_base = base;
-            break;
-        }
-    }
-
-    return final_base;
-}
-
-/// Get a constant that represents the number of times to repeat
-/// stress tests. Default 1.
-pub fn stress_factor() -> uint {
-    use os::getenv;
-    use from_str::from_str;
-
-    match getenv("RUST_RT_STRESS") {
-        Some(val) => from_str::<uint>(val).unwrap(),
-        None => 1
-    }
-}
diff --git a/src/libstd/rt/thread.rs b/src/libstd/rt/thread.rs
index 6128f310a2e..f4f4aaa2765 100644
--- a/src/libstd/rt/thread.rs
+++ b/src/libstd/rt/thread.rs
@@ -33,7 +33,7 @@ pub struct Thread<T> {
     priv packet: ~Option<T>,
 }
 
-static DEFAULT_STACK_SIZE: libc::size_t = 1024 * 1024;
+static DEFAULT_STACK_SIZE: uint = 1024 * 1024;
 
 // This is the starting point of rust os threads. The first thing we do
 // is make sure that we don't trigger __morestack (also why this has a
@@ -41,9 +41,9 @@ static DEFAULT_STACK_SIZE: libc::size_t = 1024 * 1024;
 // and invoke it.
 #[no_split_stack]
 extern fn thread_start(main: *libc::c_void) -> imp::rust_thread_return {
-    use rt::context;
+    use unstable::stack;
     unsafe {
-        context::record_stack_bounds(0, uint::max_value);
+        stack::record_stack_bounds(0, uint::max_value);
         let f: ~proc() = cast::transmute(main);
         (*f)();
         cast::transmute(0 as imp::rust_thread_return)
@@ -69,6 +69,12 @@ impl Thread<()> {
     /// called, when the `Thread` falls out of scope its destructor will block
     /// waiting for the OS thread.
     pub fn start<T: Send>(main: proc() -> T) -> Thread<T> {
+        Thread::start_stack(DEFAULT_STACK_SIZE, main)
+    }
+
+    /// Performs the same functionality as `start`, but specifies an explicit
+    /// stack size for the new thread.
+    pub fn start_stack<T: Send>(stack: uint, main: proc() -> T) -> Thread<T> {
 
         // We need the address of the packet to fill in to be stable so when
         // `main` fills it in it's still valid, so allocate an extra ~ box to do
@@ -78,7 +84,7 @@ impl Thread<()> {
             *cast::transmute::<&~Option<T>, **mut Option<T>>(&packet)
         };
         let main: proc() = proc() unsafe { *packet2 = Some(main()); };
-        let native = unsafe { imp::create(~main) };
+        let native = unsafe { imp::create(stack, ~main) };
 
         Thread {
             native: native,
@@ -94,8 +100,14 @@ impl Thread<()> {
     /// systems. Note that platforms may not keep the main program alive even if
     /// there are detached thread still running around.
     pub fn spawn(main: proc()) {
+        Thread::spawn_stack(DEFAULT_STACK_SIZE, main)
+    }
+
+    /// Performs the same functionality as `spawn`, but explicitly specifies a
+    /// stack size for the new thread.
+    pub fn spawn_stack(stack: uint, main: proc()) {
         unsafe {
-            let handle = imp::create(~main);
+            let handle = imp::create(stack, ~main);
             imp::detach(handle);
         }
     }
@@ -132,8 +144,6 @@ impl<T: Send> Drop for Thread<T> {
 
 #[cfg(windows)]
 mod imp {
-    use super::DEFAULT_STACK_SIZE;
-
     use cast;
     use libc;
     use libc::types::os::arch::extra::{LPSECURITY_ATTRIBUTES, SIZE_T, BOOL,
@@ -143,9 +153,9 @@ mod imp {
     pub type rust_thread = HANDLE;
     pub type rust_thread_return = DWORD;
 
-    pub unsafe fn create(p: ~proc()) -> rust_thread {
+    pub unsafe fn create(stack: uint, p: ~proc()) -> rust_thread {
         let arg: *mut libc::c_void = cast::transmute(p);
-        CreateThread(ptr::mut_null(), DEFAULT_STACK_SIZE, super::thread_start,
+        CreateThread(ptr::mut_null(), stack as libc::size_t, super::thread_start,
                      arg, 0, ptr::mut_null())
     }
 
@@ -183,17 +193,17 @@ mod imp {
     use libc::consts::os::posix01::PTHREAD_CREATE_JOINABLE;
     use libc;
     use ptr;
-    use super::DEFAULT_STACK_SIZE;
     use unstable::intrinsics;
 
     pub type rust_thread = libc::pthread_t;
     pub type rust_thread_return = *libc::c_void;
 
-    pub unsafe fn create(p: ~proc()) -> rust_thread {
+    pub unsafe fn create(stack: uint, p: ~proc()) -> rust_thread {
         let mut native: libc::pthread_t = intrinsics::uninit();
         let mut attr: libc::pthread_attr_t = intrinsics::uninit();
         assert_eq!(pthread_attr_init(&mut attr), 0);
-        assert_eq!(pthread_attr_setstacksize(&mut attr, DEFAULT_STACK_SIZE), 0);
+        assert_eq!(pthread_attr_setstacksize(&mut attr,
+                                             stack as libc::size_t), 0);
         assert_eq!(pthread_attr_setdetachstate(&mut attr,
                                                PTHREAD_CREATE_JOINABLE), 0);
 
diff --git a/src/libstd/rt/tube.rs b/src/libstd/rt/tube.rs
deleted file mode 100644
index 5e867bcdfba..00000000000
--- a/src/libstd/rt/tube.rs
+++ /dev/null
@@ -1,170 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! A very simple unsynchronized channel type for sending buffered data from
-//! scheduler context to task context.
-//!
-//! XXX: This would be safer to use if split into two types like Port/Chan
-
-use option::*;
-use clone::Clone;
-use super::rc::RC;
-use rt::sched::Scheduler;
-use rt::kill::BlockedTask;
-use rt::local::Local;
-use vec::OwnedVector;
-use container::Container;
-
-struct TubeState<T> {
-    blocked_task: Option<BlockedTask>,
-    buf: ~[T]
-}
-
-pub struct Tube<T> {
-    priv p: RC<TubeState<T>>
-}
-
-impl<T> Tube<T> {
-    pub fn new() -> Tube<T> {
-        Tube {
-            p: RC::new(TubeState {
-                blocked_task: None,
-                buf: ~[]
-            })
-        }
-    }
-
-    pub fn send(&mut self, val: T) {
-        rtdebug!("tube send");
-        unsafe {
-            let state = self.p.unsafe_borrow_mut();
-            (*state).buf.push(val);
-
-            if (*state).blocked_task.is_some() {
-                // There's a waiting task. Wake it up
-                rtdebug!("waking blocked tube");
-                let task = (*state).blocked_task.take_unwrap();
-                let sched: ~Scheduler = Local::take();
-                sched.resume_blocked_task_immediately(task);
-            }
-        }
-    }
-
-    pub fn recv(&mut self) -> T {
-        unsafe {
-            let state = self.p.unsafe_borrow_mut();
-            if !(*state).buf.is_empty() {
-                return (*state).buf.shift();
-            } else {
-                // Block and wait for the next message
-                rtdebug!("blocking on tube recv");
-                assert!(self.p.refcount() > 1); // There better be somebody to wake us up
-                assert!((*state).blocked_task.is_none());
-                let sched: ~Scheduler = Local::take();
-                sched.deschedule_running_task_and_then(|_, task| {
-                    (*state).blocked_task = Some(task);
-                });
-                rtdebug!("waking after tube recv");
-                let buf = &mut (*state).buf;
-                assert!(!buf.is_empty());
-                return buf.shift();
-            }
-        }
-    }
-}
-
-impl<T> Clone for Tube<T> {
-    fn clone(&self) -> Tube<T> {
-        Tube { p: self.p.clone() }
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use rt::test::*;
-    use rt::rtio::EventLoop;
-    use rt::sched::Scheduler;
-    use rt::local::Local;
-    use super::*;
-    use prelude::*;
-
-    #[test]
-    fn simple_test() {
-        do run_in_newsched_task {
-            let mut tube: Tube<int> = Tube::new();
-            let mut tube_clone = Some(tube.clone());
-            let sched: ~Scheduler = Local::take();
-            sched.deschedule_running_task_and_then(|sched, task| {
-                let mut tube_clone = tube_clone.take_unwrap();
-                tube_clone.send(1);
-                sched.enqueue_blocked_task(task);
-            });
-
-            assert!(tube.recv() == 1);
-        }
-    }
-
-    #[test]
-    fn blocking_test() {
-        do run_in_newsched_task {
-            let mut tube: Tube<int> = Tube::new();
-            let mut tube_clone = Some(tube.clone());
-            let sched: ~Scheduler = Local::take();
-            sched.deschedule_running_task_and_then(|sched, task| {
-                let tube_clone = tube_clone.take_unwrap();
-                do sched.event_loop.callback {
-                    let mut tube_clone = tube_clone;
-                    // The task should be blocked on this now and
-                    // sending will wake it up.
-                    tube_clone.send(1);
-                }
-                sched.enqueue_blocked_task(task);
-            });
-
-            assert!(tube.recv() == 1);
-        }
-    }
-
-    #[test]
-    fn many_blocking_test() {
-        static MAX: int = 100;
-
-        do run_in_newsched_task {
-            let mut tube: Tube<int> = Tube::new();
-            let mut tube_clone = Some(tube.clone());
-            let sched: ~Scheduler = Local::take();
-            sched.deschedule_running_task_and_then(|sched, task| {
-                callback_send(tube_clone.take_unwrap(), 0);
-
-                fn callback_send(tube: Tube<int>, i: int) {
-                    if i == 100 {
-                        return
-                    }
-
-                    let mut sched = Local::borrow(None::<Scheduler>);
-                    do sched.get().event_loop.callback {
-                        let mut tube = tube;
-                        // The task should be blocked on this now and
-                        // sending will wake it up.
-                        tube.send(i);
-                        callback_send(tube, i + 1);
-                    }
-                }
-
-                sched.enqueue_blocked_task(task);
-            });
-
-            for i in range(0, MAX) {
-                let j = tube.recv();
-                assert!(j == i);
-            }
-        }
-    }
-}
diff --git a/src/libstd/rt/unwind.rs b/src/libstd/rt/unwind.rs
index 3f6f54a9c0e..9706dbae4c6 100644
--- a/src/libstd/rt/unwind.rs
+++ b/src/libstd/rt/unwind.rs
@@ -8,11 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-
 // Implementation of Rust stack unwinding
 //
-// For background on exception handling and stack unwinding please see "Exception Handling in LLVM"
-// (llvm.org/docs/ExceptionHandling.html) and documents linked from it.
+// For background on exception handling and stack unwinding please see
+// "Exception Handling in LLVM" (llvm.org/docs/ExceptionHandling.html) and
+// documents linked from it.
 // These are also good reads:
 //     http://theofilos.cs.columbia.edu/blog/2013/09/22/base_abi/
 //     http://monoinfinito.wordpress.com/series/exception-handling-in-c/
@@ -21,41 +21,55 @@
 // ~~~ A brief summary ~~~
 // Exception handling happens in two phases: a search phase and a cleanup phase.
 //
-// In both phases the unwinder walks stack frames from top to bottom using information from
-// the stack frame unwind sections of the current process's modules ("module" here refers to
-// an OS module, i.e. an executable or a dynamic library).
+// In both phases the unwinder walks stack frames from top to bottom using
+// information from the stack frame unwind sections of the current process's
+// modules ("module" here refers to an OS module, i.e. an executable or a
+// dynamic library).
 //
-// For each stack frame, it invokes the associated "personality routine", whose address is also
-// stored in the unwind info section.
+// For each stack frame, it invokes the associated "personality routine", whose
+// address is also stored in the unwind info section.
 //
-// In the search phase, the job of a personality routine is to examine exception object being
-// thrown, and to decide whether it should be caught at that stack frame.  Once the handler frame
-// has been identified, cleanup phase begins.
+// In the search phase, the job of a personality routine is to examine exception
+// object being thrown, and to decide whether it should be caught at that stack
+// frame.  Once the handler frame has been identified, cleanup phase begins.
 //
-// In the cleanup phase, personality routines invoke cleanup code associated with their
-// stack frames (i.e. destructors).  Once stack has been unwound down to the handler frame level,
-// unwinding stops and the last personality routine transfers control to its' catch block.
+// In the cleanup phase, personality routines invoke cleanup code associated
+// with their stack frames (i.e. destructors).  Once stack has been unwound down
+// to the handler frame level, unwinding stops and the last personality routine
+// transfers control to its' catch block.
 //
 // ~~~ Frame unwind info registration ~~~
-// Each module has its' own frame unwind info section (usually ".eh_frame"), and unwinder needs
-// to know about all of them in order for unwinding to be able to cross module boundaries.
+// Each module has its' own frame unwind info section (usually ".eh_frame"), and
+// unwinder needs to know about all of them in order for unwinding to be able to
+// cross module boundaries.
 //
-// On some platforms, like Linux, this is achieved by dynamically enumerating currently loaded
-// modules via the dl_iterate_phdr() API and finding all .eh_frame sections.
+// On some platforms, like Linux, this is achieved by dynamically enumerating
+// currently loaded modules via the dl_iterate_phdr() API and finding all
+// .eh_frame sections.
 //
-// Others, like Windows, require modules to actively register their unwind info sections by calling
-// __register_frame_info() API at startup.
-// In the latter case it is essential that there is only one copy of the unwinder runtime
-// in the process.  This is usually achieved by linking to the dynamic version of the unwind
-// runtime.
+// Others, like Windows, require modules to actively register their unwind info
+// sections by calling __register_frame_info() API at startup.  In the latter
+// case it is essential that there is only one copy of the unwinder runtime in
+// the process.  This is usually achieved by linking to the dynamic version of
+// the unwind runtime.
 //
 // Currently Rust uses unwind runtime provided by libgcc.
 
-use prelude::*;
-use cast::transmute;
-use task::TaskResult;
+use any::{Any, AnyRefExt};
+use c_str::CString;
+use cast;
+use kinds::Send;
+use libc::{c_char, size_t};
 use libc::{c_void, c_int};
-use self::libunwind::*;
+use option::{Some, None, Option};
+use result::{Err, Ok};
+use rt::local::Local;
+use rt::task::Task;
+use str::Str;
+use task::TaskResult;
+use unstable::intrinsics;
+
+use uw = self::libunwind;
 
 mod libunwind {
     //! Unwind library interface
@@ -110,34 +124,41 @@ mod libunwind {
 }
 
 pub struct Unwinder {
-    unwinding: bool,
-    cause: Option<~Any>
+    priv unwinding: bool,
+    priv cause: Option<~Any>
 }
 
 impl Unwinder {
+    pub fn new() -> Unwinder {
+        Unwinder {
+            unwinding: false,
+            cause: None,
+        }
+    }
+
+    pub fn unwinding(&self) -> bool {
+        self.unwinding
+    }
 
     pub fn try(&mut self, f: ||) {
         use unstable::raw::Closure;
 
         unsafe {
-            let closure: Closure = transmute(f);
-            let code = transmute(closure.code);
-            let env = transmute(closure.env);
-
-            let ep = rust_try(try_fn, code, env);
+            let closure: Closure = cast::transmute(f);
+            let ep = rust_try(try_fn, closure.code as *c_void,
+                              closure.env as *c_void);
             if !ep.is_null() {
                 rtdebug!("Caught {}", (*ep).exception_class);
-                _Unwind_DeleteException(ep);
+                uw::_Unwind_DeleteException(ep);
             }
         }
 
         extern fn try_fn(code: *c_void, env: *c_void) {
             unsafe {
-                let closure: Closure = Closure {
-                    code: transmute(code),
-                    env: transmute(env),
-                };
-                let closure: || = transmute(closure);
+                let closure: || = cast::transmute(Closure {
+                    code: code as *(),
+                    env: env as *(),
+                });
                 closure();
             }
         }
@@ -145,10 +166,11 @@ impl Unwinder {
         extern {
             // Rust's try-catch
             // When f(...) returns normally, the return value is null.
-            // When f(...) throws, the return value is a pointer to the caught exception object.
+            // When f(...) throws, the return value is a pointer to the caught
+            // exception object.
             fn rust_try(f: extern "C" fn(*c_void, *c_void),
                         code: *c_void,
-                        data: *c_void) -> *_Unwind_Exception;
+                        data: *c_void) -> *uw::_Unwind_Exception;
         }
     }
 
@@ -159,21 +181,21 @@ impl Unwinder {
         self.cause = Some(cause);
 
         unsafe {
-            let exception = ~_Unwind_Exception {
+            let exception = ~uw::_Unwind_Exception {
                 exception_class: rust_exception_class(),
                 exception_cleanup: exception_cleanup,
                 private_1: 0,
                 private_2: 0
             };
-            let error = _Unwind_RaiseException(transmute(exception));
+            let error = uw::_Unwind_RaiseException(cast::transmute(exception));
             rtabort!("Could not unwind stack, error = {}", error as int)
         }
 
-        extern "C" fn exception_cleanup(_unwind_code: _Unwind_Reason_Code,
-                                        exception: *_Unwind_Exception) {
+        extern "C" fn exception_cleanup(_unwind_code: uw::_Unwind_Reason_Code,
+                                        exception: *uw::_Unwind_Exception) {
             rtdebug!("exception_cleanup()");
             unsafe {
-                let _: ~_Unwind_Exception = transmute(exception);
+                let _: ~uw::_Unwind_Exception = cast::transmute(exception);
             }
         }
     }
@@ -189,68 +211,146 @@ impl Unwinder {
 
 // Rust's exception class identifier.  This is used by personality routines to
 // determine whether the exception was thrown by their own runtime.
-fn rust_exception_class() -> _Unwind_Exception_Class {
-    let bytes = bytes!("MOZ\0RUST"); // vendor, language
-    unsafe {
-        let ptr: *_Unwind_Exception_Class = transmute(bytes.as_ptr());
-        *ptr
-    }
+fn rust_exception_class() -> uw::_Unwind_Exception_Class {
+    // M O Z \0  R U S T -- vendor, language
+    0x4d4f5a_00_52555354
 }
 
-
-// We could implement our personality routine in pure Rust, however exception info decoding
-// is tedious.  More importantly, personality routines have to handle various platform
-// quirks, which are not fun to maintain.  For this reason, we attempt to reuse personality
-// routine of the C language: __gcc_personality_v0.
+// We could implement our personality routine in pure Rust, however exception
+// info decoding is tedious.  More importantly, personality routines have to
+// handle various platform quirks, which are not fun to maintain.  For this
+// reason, we attempt to reuse personality routine of the C language:
+// __gcc_personality_v0.
 //
-// Since C does not support exception catching, __gcc_personality_v0 simply always
-// returns _URC_CONTINUE_UNWIND in search phase, and always returns _URC_INSTALL_CONTEXT
-// (i.e. "invoke cleanup code") in cleanup phase.
+// Since C does not support exception catching, __gcc_personality_v0 simply
+// always returns _URC_CONTINUE_UNWIND in search phase, and always returns
+// _URC_INSTALL_CONTEXT (i.e. "invoke cleanup code") in cleanup phase.
 //
-// This is pretty close to Rust's exception handling approach, except that Rust does have
-// a single "catch-all" handler at the bottom of each task's stack.
+// This is pretty close to Rust's exception handling approach, except that Rust
+// does have a single "catch-all" handler at the bottom of each task's stack.
 // So we have two versions:
-// - rust_eh_personality, used by all cleanup landing pads, which never catches, so
-//   the behavior of __gcc_personality_v0 is perfectly adequate there, and
-// - rust_eh_personality_catch, used only by rust_try(), which always catches.  This is
-//   achieved by overriding the return value in search phase to always say "catch!".
+// - rust_eh_personality, used by all cleanup landing pads, which never catches,
+//   so the behavior of __gcc_personality_v0 is perfectly adequate there, and
+// - rust_eh_personality_catch, used only by rust_try(), which always catches.
+//   This is achieved by overriding the return value in search phase to always
+//   say "catch!".
 
 extern "C" {
     fn __gcc_personality_v0(version: c_int,
-                            actions: _Unwind_Action,
-                            exception_class: _Unwind_Exception_Class,
-                            ue_header: *_Unwind_Exception,
-                            context: *_Unwind_Context) -> _Unwind_Reason_Code;
+                            actions: uw::_Unwind_Action,
+                            exception_class: uw::_Unwind_Exception_Class,
+                            ue_header: *uw::_Unwind_Exception,
+                            context: *uw::_Unwind_Context)
+        -> uw::_Unwind_Reason_Code;
 }
 
 #[lang="eh_personality"]
 #[no_mangle] // so we can reference it by name from middle/trans/base.rs
 #[doc(hidden)]
 #[cfg(not(test))]
-pub extern "C" fn rust_eh_personality(version: c_int,
-                                      actions: _Unwind_Action,
-                                      exception_class: _Unwind_Exception_Class,
-                                      ue_header: *_Unwind_Exception,
-                                      context: *_Unwind_Context) -> _Unwind_Reason_Code {
+pub extern "C" fn rust_eh_personality(
+    version: c_int,
+    actions: uw::_Unwind_Action,
+    exception_class: uw::_Unwind_Exception_Class,
+    ue_header: *uw::_Unwind_Exception,
+    context: *uw::_Unwind_Context
+) -> uw::_Unwind_Reason_Code
+{
     unsafe {
-        __gcc_personality_v0(version, actions, exception_class, ue_header, context)
+        __gcc_personality_v0(version, actions, exception_class, ue_header,
+                             context)
     }
 }
 
 #[no_mangle] // referenced from rust_try.ll
 #[doc(hidden)]
 #[cfg(not(test))]
-pub extern "C" fn rust_eh_personality_catch(version: c_int,
-                                            actions: _Unwind_Action,
-                                            exception_class: _Unwind_Exception_Class,
-                                            ue_header: *_Unwind_Exception,
-                                            context: *_Unwind_Context) -> _Unwind_Reason_Code {
-    if (actions as c_int & _UA_SEARCH_PHASE as c_int) != 0 { // search phase
-        _URC_HANDLER_FOUND // catch!
+pub extern "C" fn rust_eh_personality_catch(
+    version: c_int,
+    actions: uw::_Unwind_Action,
+    exception_class: uw::_Unwind_Exception_Class,
+    ue_header: *uw::_Unwind_Exception,
+    context: *uw::_Unwind_Context
+) -> uw::_Unwind_Reason_Code
+{
+    if (actions as c_int & uw::_UA_SEARCH_PHASE as c_int) != 0 { // search phase
+        uw::_URC_HANDLER_FOUND // catch!
     }
     else { // cleanup phase
         unsafe {
-             __gcc_personality_v0(version, actions, exception_class, ue_header, context)
+             __gcc_personality_v0(version, actions, exception_class, ue_header,
+                                  context)
         }
     }
 }
+
+/// This is the entry point of unwinding for things like lang items and such.
+/// The arguments are normally generated by the compiler, and need to
+/// have static lifetimes.
+pub fn begin_unwind_raw(msg: *c_char, file: *c_char, line: size_t) -> ! {
+    #[inline]
+    fn static_char_ptr(p: *c_char) -> &'static str {
+        let s = unsafe { CString::new(p, false) };
+        match s.as_str() {
+            Some(s) => unsafe { cast::transmute::<&str, &'static str>(s) },
+            None => rtabort!("message wasn't utf8?")
+        }
+    }
+
+    let msg = static_char_ptr(msg);
+    let file = static_char_ptr(file);
+
+    begin_unwind(msg, file, line as uint)
+}
+
+/// This is the entry point of unwinding for fail!() and assert!().
+pub fn begin_unwind<M: Any + Send>(msg: M, file: &'static str, line: uint) -> ! {
+    unsafe {
+        let task: *mut Task;
+        // Note that this should be the only allocation performed in this block.
+        // Currently this means that fail!() on OOM will invoke this code path,
+        // but then again we're not really ready for failing on OOM anyway. If
+        // we do start doing this, then we should propagate this allocation to
+        // be performed in the parent of this task instead of the task that's
+        // failing.
+        let msg = ~msg as ~Any;
+
+        {
+            let msg_s = match msg.as_ref::<&'static str>() {
+                Some(s) => *s,
+                None => match msg.as_ref::<~str>() {
+                    Some(s) => s.as_slice(),
+                    None => "~Any",
+                }
+            };
+
+            // It is assumed that all reasonable rust code will have a local
+            // task at all times. This means that this `try_unsafe_borrow` will
+            // succeed almost all of the time. There are border cases, however,
+            // when the runtime has *almost* set up the local task, but hasn't
+            // quite gotten there yet. In order to get some better diagnostics,
+            // we print on failure and immediately abort the whole process if
+            // there is no local task available.
+            match Local::try_unsafe_borrow() {
+                Some(t) => {
+                    task = t;
+                    let n = (*task).name.as_ref()
+                                   .map(|n| n.as_slice()).unwrap_or("<unnamed>");
+
+                    rterrln!("task '{}' failed at '{}', {}:{}", n, msg_s,
+                             file, line);
+                }
+                None => {
+                    rterrln!("failed at '{}', {}:{}", msg_s, file, line);
+                    intrinsics::abort();
+                }
+            }
+
+            if (*task).unwinder.unwinding {
+                rtabort!("unwinding again");
+            }
+        }
+
+        (*task).unwinder.begin_unwind(msg);
+    }
+}
diff --git a/src/libstd/rt/util.rs b/src/libstd/rt/util.rs
index 93721986f3c..730a38ce886 100644
--- a/src/libstd/rt/util.rs
+++ b/src/libstd/rt/util.rs
@@ -15,7 +15,6 @@ use libc;
 use option::{Some, None, Option};
 use os;
 use str::StrSlice;
-use unstable::atomics::{AtomicInt, INIT_ATOMIC_INT, SeqCst};
 use unstable::running_on_valgrind;
 
 // Indicates whether we should perform expensive sanity checks, including rtassert!
@@ -68,11 +67,21 @@ pub fn default_sched_threads() -> uint {
 }
 
 pub fn dumb_println(args: &fmt::Arguments) {
-    use io::native::file::FileDesc;
     use io;
     use libc;
-    let mut out = FileDesc::new(libc::STDERR_FILENO, false);
-    fmt::writeln(&mut out as &mut io::Writer, args);
+
+    struct Stderr;
+    impl io::Writer for Stderr {
+        fn write(&mut self, data: &[u8]) {
+            unsafe {
+                libc::write(libc::STDERR_FILENO,
+                            data.as_ptr() as *libc::c_void,
+                            data.len() as libc::size_t);
+            }
+        }
+    }
+    let mut w = Stderr;
+    fmt::writeln(&mut w as &mut io::Writer, args);
 }
 
 pub fn abort(msg: &str) -> ! {
@@ -133,13 +142,3 @@ memory and partly incapable of presentation to others.",
         unsafe { libc::abort() }
     }
 }
-
-static mut EXIT_STATUS: AtomicInt = INIT_ATOMIC_INT;
-
-pub fn set_exit_status(code: int) {
-    unsafe { EXIT_STATUS.store(code, SeqCst) }
-}
-
-pub fn get_exit_status() -> int {
-    unsafe { EXIT_STATUS.load(SeqCst) }
-}