Fix for locking the predicate change in the set method.

Thanks to @FernetMenta for pointing out the issue with setting the without holding the lock predicate. It's possible that the predicate is changed between the check and the wait() in the Wait* call. This fixes that problem.

1 files changed, 10 insertions, 2 deletions

diff --git a/xbmc/threads/Event.cpp b/xbmc/threads/Event.cpp
index adaa490678..d658cc463b 100644
--- a/xbmc/threads/Event.cpp
+++ b/xbmc/threads/Event.cpp
@@ -58,8 +58,16 @@ void CEvent::removeGroup(XbmcThreads::CEventGroup* group)
 //  CEvent::groupListMutex -> CEventGroup::mutex -> CEvent::mutex
 void CEvent::Set()
 {
-  // no locking necessary
-  signaled = true; 
+  // Originally I had this without locking. Thanks to FernetMenta who
+  // pointed out that this creates a race condition between setting
+  // checking the signal and calling wait() on the Wait call in the
+  // CEvent class. This now perfectly matches the boost example here:
+  // http://www.boost.org/doc/libs/1_41_0/doc/html/thread/synchronization.html#thread.synchronization.condvar_ref
+  {
+    CSingleLock slock(mutex);
+    signaled = true; 
+  }
+
   condVar.notifyAll();
 
   CSingleLock l(groupListMutex);