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).

1 files changed, 217 insertions, 0 deletions

diff --git a/src/libstd/sync/mpmc_bounded_queue.rs b/src/libstd/sync/mpmc_bounded_queue.rs
new file mode 100644
index 00000000000..fe51de4e42d
--- /dev/null
+++ b/src/libstd/sync/mpmc_bounded_queue.rs
@@ -0,0 +1,217 @@
+/* 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.
+ */
+
+#[allow(missing_doc, dead_code)];
+
+// http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue
+
+use clone::Clone;
+use kinds::Send;
+use num::{Exponential,Algebraic,Round};
+use option::{Option, Some, None};
+use sync::arc::UnsafeArc;
+use sync::atomics::{AtomicUint,Relaxed,Release,Acquire};
+use vec;
+
+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 super::Queue;
+    use native;
+
+    #[test]
+    fn test() {
+        let nthreads = 8u;
+        let nmsgs = 1000u;
+        let mut q = Queue::with_capacity(nthreads*nmsgs);
+        assert_eq!(None, q.pop());
+        let (port, chan) = SharedChan::new();
+
+        for _ in range(0, nthreads) {
+            let q = q.clone();
+            let chan = chan.clone();
+            do native::task::spawn {
+                let mut q = q;
+                for i in range(0, nmsgs) {
+                    assert!(q.push(i));
+                }
+                chan.send(());
+            }
+        }
+
+        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 native::task::spawn {
+                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());
+        }
+        for _ in range(0, nthreads) {
+            port.recv();
+        }
+    }
+}