Adding locking to webrtc::voe::Channel to fix race conditions

webrtc/voice_engine/channel.h

Index: webrtc/voice_engine/channel.h
diff --git a/webrtc/voice_engine/channel.h b/webrtc/voice_engine/channel.h
index 398087eefb481a0cd96624b6b086c3d9c0acbe58..ad2471654e905bc469de06b544a8126fd8a72205 100644
--- a/webrtc/voice_engine/channel.h
+++ b/webrtc/voice_engine/channel.h
@@ -274,7 +274,10 @@ public:
     // VoEVideoSync
     bool GetDelayEstimate(int* jitter_buffer_delay_ms,
                           int* playout_buffer_delay_ms) const;
-    int least_required_delay_ms() const { return least_required_delay_ms_; }
+    int least_required_delay_ms() const {
+      CriticalSectionScoped cs(&video_sync_critsect_);

[the sun, 2015/08/04 09:36:47]

It looks like this function could call audio_coding_->LeastRequiredDelayMs()
directly, skipping the lock (already locked lowere down) and local caching of
the value.

 hlundin@, is there a reason why that wouldn't work?

[hlundin-webrtc, 2015/08/04 09:52:10]

That should work.

[Taylor Brandstetter, 2015/08/05 03:04:48]

Done.

+      return least_required_delay_ms_;
+    }
     int SetInitialPlayoutDelay(int delay_ms);
     int SetMinimumPlayoutDelay(int delayMs);
     int GetPlayoutTimestamp(unsigned int& timestamp);
@@ -478,6 +481,7 @@ private:
     CriticalSectionWrapper& _fileCritSect;
     CriticalSectionWrapper& _callbackCritSect;
     CriticalSectionWrapper& volume_settings_critsect_;
+    CriticalSectionWrapper& video_sync_critsect_;

[hlundin-webrtc, 2015/08/04 06:56:46]

Please, add GUARDED_BY(video_sync_critsect_) on the member variables that are
protected by this lock. It is provided by webrtc/base/thread_annotations.h.

[Taylor Brandstetter, 2015/08/05 03:04:48]

Done.

     uint32_t _instanceId;
     int32_t _channelId;