3 files changed, 3 insertions, 0 deletions
diff --git a/src/libstd/sync/condvar.rs b/src/libstd/sync/condvar.rs
index 4c946e613ea..3db8b05b954 100644
--- a/src/libstd/sync/condvar.rs
+++ b/src/libstd/sync/condvar.rs
@@ -241,6 +241,7 @@ impl Condvar {
 
 #[stable(feature = "condvar_default", since = "1.9.0")]
 impl Default for Condvar {
+    /// Creates a `Condvar` which is ready to be waited on and notified.
     fn default() -> Condvar {
         Condvar::new()
     }
diff --git a/src/libstd/sync/mutex.rs b/src/libstd/sync/mutex.rs
index c8ae88c2331..098a3e44258 100644
--- a/src/libstd/sync/mutex.rs
+++ b/src/libstd/sync/mutex.rs
@@ -287,6 +287,7 @@ impl<T: ?Sized> Drop for Mutex<T> {
 
 #[stable(feature = "mutex_default", since = "1.9.0")]
 impl<T: ?Sized + Default> Default for Mutex<T> {
+    /// Creates a `Mutex<T>`, with the `Default` value for T.
     fn default() -> Mutex<T> {
         Mutex::new(Default::default())
     }
diff --git a/src/libstd/sync/rwlock.rs b/src/libstd/sync/rwlock.rs
index 4801bcffd08..7f053c6704b 100644
--- a/src/libstd/sync/rwlock.rs
+++ b/src/libstd/sync/rwlock.rs
@@ -311,6 +311,7 @@ impl<T: ?Sized + fmt::Debug> fmt::Debug for RwLock<T> {
 
 #[stable(feature = "rw_lock_default", since = "1.9.0")]
 impl<T: Default> Default for RwLock<T> {
+    /// Creates a new `RwLock<T>`, with the `Default` value for T.
     fn default() -> RwLock<T> {
         RwLock::new(Default::default())
     }