2 files changed, 11 insertions, 5 deletions
diff --git a/src/libstd/sync/mutex.rs b/src/libstd/sync/mutex.rs
index 4829be569cc..2849813c510 100644
--- a/src/libstd/sync/mutex.rs
+++ b/src/libstd/sync/mutex.rs
@@ -10,7 +10,7 @@
 
 use prelude::*;
 
-use cell::UnsafeCell;
+use cell::{UnsafeCell, RacyCell};
 use kinds::marker;
 use sync::{poison, AsMutexGuard};
 use sys_common::mutex as sys;
@@ -70,9 +70,13 @@ pub struct Mutex<T> {
     // time, so to ensure that the native mutex is used correctly we box the
     // inner lock to give it a constant address.
     inner: Box<StaticMutex>,
-    data: UnsafeCell<T>,
+    data: RacyCell<T>,
 }
 
+impl<T:Send> Send for Mutex<T> { }
+
+impl<T:Send> Sync for Mutex<T> { }
+
 /// The static mutex type is provided to allow for static allocation of mutexes.
 ///
 /// Note that this is a separate type because using a Mutex correctly means that
@@ -94,9 +98,10 @@ pub struct Mutex<T> {
 /// }
 /// // lock is unlocked here.
 /// ```
+#[deriving(Sync)]
 pub struct StaticMutex {
     lock: sys::Mutex,
-    poison: UnsafeCell<poison::Flag>,
+    poison: RacyCell<poison::Flag>,
 }
 
 /// An RAII implementation of a "scoped lock" of a mutex. When this structure is
@@ -125,7 +130,7 @@ pub struct StaticMutexGuard {
 /// other mutex constants.
 pub const MUTEX_INIT: StaticMutex = StaticMutex {
     lock: sys::MUTEX_INIT,
-    poison: UnsafeCell { value: poison::Flag { failed: false } },
+    poison: RacyCell(UnsafeCell { value: poison::Flag { failed: false } }),
 };
 
 impl<T: Send> Mutex<T> {
@@ -133,7 +138,7 @@ impl<T: Send> Mutex<T> {
     pub fn new(t: T) -> Mutex<T> {
         Mutex {
             inner: box MUTEX_INIT,
-            data: UnsafeCell::new(t),
+            data: RacyCell::new(t),
         }
     }
 
diff --git a/src/libstd/sync/once.rs b/src/libstd/sync/once.rs
index a43f822e351..4b940b0420a 100644
--- a/src/libstd/sync/once.rs
+++ b/src/libstd/sync/once.rs
@@ -35,6 +35,7 @@ use sync::{StaticMutex, MUTEX_INIT};
 ///     // run initialization here
 /// });
 /// ```
+#[deriving(Sync)]
 pub struct Once {
     mutex: StaticMutex,
     cnt: atomic::AtomicInt,