Bug 1240622 - Guard mCheckerboardEvent with a mutex to avoid races. r=botond

--HG--
extra : commitid : 9LLumoyfORc

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -862,7 +862,8 @@ AsyncPanZoomController::AsyncPanZoomController(uint64_t aLayersId,
      mInputQueue(aInputQueue),
      mAPZCId(sAsyncPanZoomControllerCount++),
      mSharedLock(nullptr),
-     mAsyncTransformAppliedToContent(false)
+     mAsyncTransformAppliedToContent(false),
+     mCheckerboardEventLock("APZCBELock")
 {
   if (aGestures == USE_GESTURE_DETECTOR) {
     mGestureEventListener = new GestureEventListener(this);
@@ -2871,6 +2872,8 @@ AsyncPanZoomController::RequestContentRepaint(const FrameMetrics& aFrameMetrics,
   }
 
   APZC_LOG_FM(aFrameMetrics, "%p requesting content repaint", this);
+  { // scope lock
+    MutexAutoLock lock(mCheckerboardEventLock);
     if (mCheckerboardEvent && mCheckerboardEvent->IsRecordingTrace()) {
       std::stringstream info;
       info << " velocity " << aVelocity;
@@ -2879,6 +2882,7 @@ AsyncPanZoomController::RequestContentRepaint(const FrameMetrics& aFrameMetrics,
           CheckerboardEvent::RequestedDisplayPort, GetDisplayPortRect(aFrameMetrics),
           str);
     }
+  }
 
   controller->RequestContentRepaint(aFrameMetrics);
   mExpectedGeckoMetrics = aFrameMetrics;
@@ -2981,6 +2985,8 @@ bool AsyncPanZoomController::AdvanceAnimations(const TimeStamp& aSampleTime)
 
     requestAnimationFrame = UpdateAnimation(aSampleTime, &deferredTasks);
 
+    { // scope lock
+      MutexAutoLock lock(mCheckerboardEventLock);
       if (mCheckerboardEvent) {
         mCheckerboardEvent->UpdateRendertraceProperty(
             CheckerboardEvent::UserVisible,
@@ -2988,6 +2994,7 @@ bool AsyncPanZoomController::AdvanceAnimations(const TimeStamp& aSampleTime)
                     mFrameMetrics.CalculateCompositedSizeInCssPixels()));
       }
     }
+  }
 
   // Execute any deferred tasks queued up by mAnimation's Sample() (called by
   // UpdateAnimation()). This needs to be done after the monitor is released
@@ -3106,10 +3113,12 @@ AsyncPanZoomController::ReportCheckerboard(const TimeStamp& aSampleTime)
 
   bool recordTrace = gfxPrefs::APZRecordCheckerboarding();
   bool forTelemetry = Telemetry::CanRecordExtended();
+  uint32_t magnitude = GetCheckerboardMagnitude();
+
+  MutexAutoLock lock(mCheckerboardEventLock);
   if (!mCheckerboardEvent && (recordTrace || forTelemetry)) {
     mCheckerboardEvent = MakeUnique<CheckerboardEvent>(recordTrace);
   }
-  uint32_t magnitude = GetCheckerboardMagnitude();
   if (magnitude) {
     mPotentialCheckerboardTracker.CheckerboardSeen();
   }
@@ -3168,6 +3177,8 @@ void AsyncPanZoomController::NotifyLayersUpdated(const FrameMetrics& aLayerMetri
   APZC_LOG_FM(aLayerMetrics, "%p got a NotifyLayersUpdated with aIsFirstPaint=%d, aThisLayerTreeUpdated=%d",
     this, aIsFirstPaint, aThisLayerTreeUpdated);
 
+  { // scope lock
+    MutexAutoLock lock(mCheckerboardEventLock);
     if (mCheckerboardEvent && mCheckerboardEvent->IsRecordingTrace()) {
       std::string str;
       if (aThisLayerTreeUpdated) {
@@ -3200,6 +3211,7 @@ void AsyncPanZoomController::NotifyLayersUpdated(const FrameMetrics& aLayerMetri
             aLayerMetrics.GetCriticalDisplayPort() + aLayerMetrics.GetScrollOffset());
       }
     }
+  }
 
   bool needContentRepaint = false;
   bool viewportUpdated = false;

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -1102,6 +1102,8 @@ private:
    * recording.
    */
 private:
+  // Mutex protecting mCheckerboardEvent
+  Mutex mCheckerboardEventLock;
   // This is created when this APZC instance is first included as part of a
   // composite. If a checkerboard event takes place, this is destroyed at the
   // end of the event, and a new one is created on the next composite.