Merge pull request rust-lang#219 from dwrensha/seq-cst

Use SeqCst instead of Acquire and Release in Lock.

Author: alexcrichton

src/lock.rs

@@ -8,7 +8,7 @@ extern crate core;
 
 use self::core::cell::UnsafeCell;
 use self::core::ops::{Deref, DerefMut};
-use self::core::sync::atomic::Ordering::{Acquire, Release};
+use self::core::sync::atomic::Ordering::{SeqCst};
 use self::core::sync::atomic::AtomicBool;
 
 /// A "mutex" around a value, similar to `std::sync::Mutex<T>`.
@@ -54,7 +54,7 @@ impl<T> Lock<T> {
     /// If `None` is returned then the lock is already locked, either elsewhere
     /// on this thread or on another thread.
     pub fn try_lock(&self) -> Option<TryLock<T>> {
-        if !self.locked.swap(true, Acquire) {
+        if !self.locked.swap(true, SeqCst) {
             Some(TryLock { __ptr: self })
         } else {
             None
@@ -84,7 +84,7 @@ impl<'a, T> DerefMut for TryLock<'a, T> {
 
 impl<'a, T> Drop for TryLock<'a, T> {
     fn drop(&mut self) {
-        self.__ptr.locked.store(false, Release);
+        self.__ptr.locked.store(false, SeqCst);
     }
 }