Bug 848954 - Part 13 - Add an RAII class to ensure another thread is not in the audio callback when shutting down. r=roc

content/media/GraphDriver.cpp

@@ -551,11 +551,30 @@ AudioCallbackDriver::StateCallback_s(cubeb_stream* aStream, void * aUser,
   driver->StateCallback(aState);
 }
 
+bool AudioCallbackDriver::InCallback() {
+  MonitorAutoLock mon(mGraphImpl->GetMonitor());
+  return mInCallback;
+}
+
+AudioCallbackDriver::AutoInCallback::AutoInCallback(AudioCallbackDriver* aDriver)
+  : mDriver(aDriver)
+{
+  MonitorAutoLock mon(mDriver->mGraphImpl->GetMonitor());
+  mDriver->mInCallback = true;
+}
+
+AudioCallbackDriver::AutoInCallback::~AutoInCallback() {
+  MonitorAutoLock mon(mDriver->mGraphImpl->GetMonitor());
+  mDriver->mInCallback = false;
+}
+
 long
 AudioCallbackDriver::DataCallback(AudioDataValue* aBuffer, long aFrames)
 {
   bool stillProcessing;
 
+  DebugOnly<AutoInCallback> aic(this);
+
   if (mStateComputedTime == 0) {
     MonitorAutoLock mon(mGraphImpl->GetMonitor());
     // Because this function is called during cubeb_stream_init (to prefill the

content/media/GraphDriver.h

@@ -143,6 +143,8 @@ public:
     MOZ_CRASH("This is not an Audio GraphDriver!");
   }
 
+  bool InCallback();
+
   virtual AudioCallbackDriver* AsAudioCallbackDriver() {
     return nullptr;
   }
@@ -439,6 +441,16 @@ private:
    * This is synchronized by the Graph's monitor.
    * */
   bool mStarted;
+  /* This can only be accessed with the graph's monitor held. */
+  bool mInCallback;
+
+  struct AutoInCallback
+  {
+    AutoInCallback(AudioCallbackDriver* aDriver);
+    ~AutoInCallback();
+    AudioCallbackDriver* mDriver;
+  };
+
 };
 
 }

content/media/MediaStreamGraph.cpp

@@ -1490,6 +1490,10 @@ public:
     NS_ASSERTION(mGraph->mDetectedNotRunning,
                  "We should know the graph thread control loop isn't running!");
 
+    if (mGraph->CurrentDriver()->AsAudioCallbackDriver()) {
+      MOZ_ASSERT(!mGraph->CurrentDriver()->AsAudioCallbackDriver()->InCallback());
+    }
+
     STREAM_LOG(PR_LOG_DEBUG, ("Shutting drown graph %p", mGraph));
 
     // mGraph's thread is not running so it's OK to do whatever here