diff options
Diffstat (limited to 'src/libsync')
| -rw-r--r-- | src/libsync/arc.rs | 387 | ||||
| -rw-r--r-- | src/libsync/lib.rs | 5 | ||||
| -rw-r--r-- | src/libsync/lock.rs | 2 | ||||
| -rw-r--r-- | src/libsync/raw.rs | 2 |
4 files changed, 5 insertions, 391 deletions
diff --git a/src/libsync/arc.rs b/src/libsync/arc.rs deleted file mode 100644 index 26d7e04fe1d..00000000000 --- a/src/libsync/arc.rs +++ /dev/null @@ -1,387 +0,0 @@ -// Copyright 2012-2014 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. - -/*! - * Concurrency-enabled mechanisms for sharing mutable and/or immutable state - * between tasks. - */ - -use std::mem; -use std::ptr; -use std::rt::heap::deallocate; -use std::sync::atomics; -use std::mem::{min_align_of, size_of}; - -/// An atomically reference counted wrapper for shared state. -/// -/// # Example -/// -/// In this example, a large vector of floats is shared between several tasks. -/// With simple pipes, without `Arc`, a copy would have to be made for each -/// task. -/// -/// ```rust -/// use sync::Arc; -/// -/// fn main() { -/// let numbers = Vec::from_fn(100, |i| i as f32); -/// let shared_numbers = Arc::new(numbers); -/// -/// for _ in range(0, 10) { -/// let child_numbers = shared_numbers.clone(); -/// -/// spawn(proc() { -/// let local_numbers = child_numbers.as_slice(); -/// -/// // Work with the local numbers -/// }); -/// } -/// } -/// ``` -#[unsafe_no_drop_flag] -pub struct Arc<T> { - x: *mut ArcInner<T>, -} - -/// A weak pointer to an `Arc`. -/// -/// Weak pointers will not keep the data inside of the `Arc` alive, and can be -/// used to break cycles between `Arc` pointers. -#[unsafe_no_drop_flag] -pub struct Weak<T> { - x: *mut ArcInner<T>, -} - -struct ArcInner<T> { - strong: atomics::AtomicUint, - weak: atomics::AtomicUint, - data: T, -} - -impl<T: Share + Send> Arc<T> { - /// Create an atomically reference counted wrapper. - #[inline] - pub fn new(data: T) -> Arc<T> { - // Start the weak pointer count as 1 which is the weak pointer that's - // held by all the strong pointers (kinda), see std/rc.rs for more info - let x = box ArcInner { - strong: atomics::AtomicUint::new(1), - weak: atomics::AtomicUint::new(1), - data: data, - }; - Arc { x: unsafe { mem::transmute(x) } } - } - - #[inline] - fn inner<'a>(&'a self) -> &'a ArcInner<T> { - // This unsafety is ok because while this arc is alive we're guaranteed - // that the inner pointer is valid. Furthermore, we know that the - // `ArcInner` structure itself is `Share` because the inner data is - // `Share` as well, so we're ok loaning out an immutable pointer to - // these contents. - unsafe { &*self.x } - } - - /// Downgrades a strong pointer to a weak pointer - /// - /// Weak pointers will not keep the data alive. Once all strong references - /// to the underlying data have been dropped, the data itself will be - /// destroyed. - pub fn downgrade(&self) -> Weak<T> { - // See the clone() impl for why this is relaxed - self.inner().weak.fetch_add(1, atomics::Relaxed); - Weak { x: self.x } - } -} - -impl<T: Share + Send> Clone for Arc<T> { - /// Duplicate an atomically reference counted wrapper. - /// - /// The resulting two `Arc` objects will point to the same underlying data - /// object. However, one of the `Arc` objects can be sent to another task, - /// allowing them to share the underlying data. - #[inline] - fn clone(&self) -> Arc<T> { - // Using a relaxed ordering is alright here, as knowledge of the - // original reference prevents other threads from erroneously deleting - // the object. - // - // As explained in the [Boost documentation][1], Increasing the - // reference counter can always be done with memory_order_relaxed: New - // references to an object can only be formed from an existing - // reference, and passing an existing reference from one thread to - // another must already provide any required synchronization. - // - // [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html) - self.inner().strong.fetch_add(1, atomics::Relaxed); - Arc { x: self.x } - } -} - -impl<T: Send + Share> Deref<T> for Arc<T> { - #[inline] - fn deref<'a>(&'a self) -> &'a T { - &self.inner().data - } -} - -impl<T: Send + Share + Clone> Arc<T> { - /// Acquires a mutable pointer to the inner contents by guaranteeing that - /// the reference count is one (no sharing is possible). - /// - /// This is also referred to as a copy-on-write operation because the inner - /// data is cloned if the reference count is greater than one. - #[inline] - #[experimental] - pub fn make_unique<'a>(&'a mut self) -> &'a mut T { - if self.inner().strong.load(atomics::SeqCst) != 1 { - *self = Arc::new(self.deref().clone()) - } - // This unsafety is ok because we're guaranteed that the pointer - // returned is the *only* pointer that will ever be returned to T. Our - // reference count is guaranteed to be 1 at this point, and we required - // the Arc itself to be `mut`, so we're returning the only possible - // reference to the inner data. - unsafe { mem::transmute::<&_, &mut _>(self.deref()) } - } -} - -#[unsafe_destructor] -impl<T: Share + Send> Drop for Arc<T> { - fn drop(&mut self) { - // This structure has #[unsafe_no_drop_flag], so this drop glue may run - // more than once (but it is guaranteed to be zeroed after the first if - // it's run more than once) - if self.x.is_null() { return } - - // Because `fetch_sub` is already atomic, we do not need to synchronize - // with other threads unless we are going to delete the object. This - // same logic applies to the below `fetch_sub` to the `weak` count. - if self.inner().strong.fetch_sub(1, atomics::Release) != 1 { return } - - // This fence is needed to prevent reordering of use of the data and - // deletion of the data. Because it is marked `Release`, the - // decreasing of the reference count sychronizes with this `Acquire` - // fence. This means that use of the data happens before decreasing - // the refernce count, which happens before this fence, which - // happens before the deletion of the data. - // - // As explained in the [Boost documentation][1], - // - // It is important to enforce any possible access to the object in - // one thread (through an existing reference) to *happen before* - // deleting the object in a different thread. This is achieved by a - // "release" operation after dropping a reference (any access to the - // object through this reference must obviously happened before), - // and an "acquire" operation before deleting the object. - // - // [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html) - atomics::fence(atomics::Acquire); - - // Destroy the data at this time, even though we may not free the box - // allocation itself (there may still be weak pointers lying around). - unsafe { drop(ptr::read(&self.inner().data)); } - - if self.inner().weak.fetch_sub(1, atomics::Release) == 1 { - atomics::fence(atomics::Acquire); - unsafe { deallocate(self.x as *mut u8, size_of::<ArcInner<T>>(), - min_align_of::<ArcInner<T>>()) } - } - } -} - -impl<T: Share + Send> Weak<T> { - /// Attempts to upgrade this weak reference to a strong reference. - /// - /// This method will fail to upgrade this reference if the strong reference - /// count has already reached 0, but if there are still other active strong - /// references this function will return a new strong reference to the data - pub fn upgrade(&self) -> Option<Arc<T>> { - // We use a CAS loop to increment the strong count instead of a - // fetch_add because once the count hits 0 is must never be above 0. - let inner = self.inner(); - loop { - let n = inner.strong.load(atomics::SeqCst); - if n == 0 { return None } - let old = inner.strong.compare_and_swap(n, n + 1, atomics::SeqCst); - if old == n { return Some(Arc { x: self.x }) } - } - } - - #[inline] - fn inner<'a>(&'a self) -> &'a ArcInner<T> { - // See comments above for why this is "safe" - unsafe { &*self.x } - } -} - -impl<T: Share + Send> Clone for Weak<T> { - #[inline] - fn clone(&self) -> Weak<T> { - // See comments in Arc::clone() for why this is relaxed - self.inner().weak.fetch_add(1, atomics::Relaxed); - Weak { x: self.x } - } -} - -#[unsafe_destructor] -impl<T: Share + Send> Drop for Weak<T> { - fn drop(&mut self) { - // see comments above for why this check is here - if self.x.is_null() { return } - - // If we find out that we were the last weak pointer, then its time to - // deallocate the data entirely. See the discussion in Arc::drop() about - // the memory orderings - if self.inner().weak.fetch_sub(1, atomics::Release) == 1 { - atomics::fence(atomics::Acquire); - unsafe { deallocate(self.x as *mut u8, size_of::<ArcInner<T>>(), - min_align_of::<ArcInner<T>>()) } - } - } -} - -#[cfg(test)] -#[allow(experimental)] -mod tests { - use super::{Arc, Weak}; - use std::sync::atomics; - use std::task; - use Mutex; - - struct Canary(*mut atomics::AtomicUint); - - impl Drop for Canary - { - fn drop(&mut self) { - unsafe { - match *self { - Canary(c) => { - (*c).fetch_add(1, atomics::SeqCst); - } - } - } - } - } - - #[test] - fn manually_share_arc() { - let v = vec!(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); - let arc_v = Arc::new(v); - - let (tx, rx) = channel(); - - task::spawn(proc() { - let arc_v: Arc<Vec<int>> = rx.recv(); - assert_eq!(*arc_v.get(3), 4); - }); - - tx.send(arc_v.clone()); - - assert_eq!(*arc_v.get(2), 3); - assert_eq!(*arc_v.get(4), 5); - - info!("{:?}", arc_v); - } - - #[test] - fn test_cowarc_clone_make_unique() { - let mut cow0 = Arc::new(75u); - let mut cow1 = cow0.clone(); - let mut cow2 = cow1.clone(); - - assert!(75 == *cow0.make_unique()); - assert!(75 == *cow1.make_unique()); - assert!(75 == *cow2.make_unique()); - - *cow0.make_unique() += 1; - *cow1.make_unique() += 2; - *cow2.make_unique() += 3; - - assert!(76 == *cow0); - assert!(77 == *cow1); - assert!(78 == *cow2); - - // none should point to the same backing memory - assert!(*cow0 != *cow1); - assert!(*cow0 != *cow2); - assert!(*cow1 != *cow2); - } - - #[test] - fn test_cowarc_clone_unique2() { - let mut cow0 = Arc::new(75u); - let cow1 = cow0.clone(); - let cow2 = cow1.clone(); - - assert!(75 == *cow0); - assert!(75 == *cow1); - assert!(75 == *cow2); - - *cow0.make_unique() += 1; - - assert!(76 == *cow0); - assert!(75 == *cow1); - assert!(75 == *cow2); - - // cow1 and cow2 should share the same contents - // cow0 should have a unique reference - assert!(*cow0 != *cow1); - assert!(*cow0 != *cow2); - assert!(*cow1 == *cow2); - } - - #[test] - fn test_live() { - let x = Arc::new(5); - let y = x.downgrade(); - assert!(y.upgrade().is_some()); - } - - #[test] - fn test_dead() { - let x = Arc::new(5); - let y = x.downgrade(); - drop(x); - assert!(y.upgrade().is_none()); - } - - #[test] - fn weak_self_cyclic() { - struct Cycle { - x: Mutex<Option<Weak<Cycle>>> - } - - let a = Arc::new(Cycle { x: Mutex::new(None) }); - let b = a.clone().downgrade(); - *a.deref().x.lock().deref_mut() = Some(b); - - // hopefully we don't double-free (or leak)... - } - - #[test] - fn drop_arc() { - let mut canary = atomics::AtomicUint::new(0); - let x = Arc::new(Canary(&mut canary as *mut atomics::AtomicUint)); - drop(x); - assert!(canary.load(atomics::Acquire) == 1); - } - - #[test] - fn drop_arc_weak() { - let mut canary = atomics::AtomicUint::new(0); - let arc = Arc::new(Canary(&mut canary as *mut atomics::AtomicUint)); - let arc_weak = arc.downgrade(); - assert!(canary.load(atomics::Acquire) == 0); - drop(arc); - assert!(canary.load(atomics::Acquire) == 1); - drop(arc_weak); - } -} diff --git a/src/libsync/lib.rs b/src/libsync/lib.rs index e5d506301e3..3396425928e 100644 --- a/src/libsync/lib.rs +++ b/src/libsync/lib.rs @@ -27,17 +27,18 @@ #[cfg(test)] #[phase(syntax, link)] extern crate log; +extern crate alloc; + pub use comm::{DuplexStream, duplex}; pub use task_pool::TaskPool; pub use future::Future; -pub use arc::{Arc, Weak}; +pub use alloc::arc::{Arc, Weak}; pub use lock::{Mutex, MutexGuard, Condvar, Barrier, RWLock, RWLockReadGuard, RWLockWriteGuard}; // The mutex/rwlock in this module are not meant for reexport pub use raw::{Semaphore, SemaphoreGuard}; -mod arc; mod comm; mod future; mod lock; diff --git a/src/libsync/lock.rs b/src/libsync/lock.rs index 930b3009042..9f59f587770 100644 --- a/src/libsync/lock.rs +++ b/src/libsync/lock.rs @@ -447,7 +447,7 @@ mod tests { use std::task; use std::task::TaskBuilder; - use arc::Arc; + use Arc; use super::{Mutex, Barrier, RWLock}; #[test] diff --git a/src/libsync/raw.rs b/src/libsync/raw.rs index 990aba3ebff..591318d24b2 100644 --- a/src/libsync/raw.rs +++ b/src/libsync/raw.rs @@ -622,7 +622,7 @@ impl<'a> Drop for RWLockReadGuard<'a> { #[cfg(test)] mod tests { - use arc::Arc; + use Arc; use super::{Semaphore, Mutex, RWLock, Condvar}; use std::mem; |