bug 1408276 move to LIFECYCLE_WAITING_FOR_MAIN_THREAD_CLEANUP at end of iteration f=pehrsons r=padenot

MozReview-Commit-ID: GbfIOPZPuGu

--HG--
extra : rebase_source : 8a7abbe8a96a90f20dbb0465b6a5f69f05140d4f
extra : amend_source : 41079a2a825b53ed6d4e8cc31fc4c8de2f041e8b
extra : histedit_source : df5b962ac253df34ace8ebc22cdd98b608b6ddfb

dom/media/GraphDriver.cpp

@@ -284,8 +284,7 @@ SystemClockDriver::IsFallback()
 void
 ThreadedDriver::RunThread()
 {
-  bool stillProcessing = true;
-  while (stillProcessing) {
+  while (true) {
     mIterationStart = IterationEnd();
     mIterationEnd += GetIntervalForIteration();
 
@@ -324,10 +323,16 @@ ThreadedDriver::RunThread()
          (long)stateComputedTime,
          (long)nextStateComputedTime));
 
-    stillProcessing = mGraphImpl->OneIteration(nextStateComputedTime);
+    bool stillProcessing = mGraphImpl->OneIteration(nextStateComputedTime);
 
+    if (!stillProcessing) {
+      // Enter shutdown mode. The stable-state handler will detect this
+      // and complete shutdown if the graph does not get restarted.
+      mGraphImpl->SignalMainThreadCleanup();
+      return;
+    }
     MonitorAutoLock lock(GraphImpl()->GetMonitor());
-    if (NextDriver() && stillProcessing) {
+    if (NextDriver()) {
       LOG(LogLevel::Debug, ("Switching to AudioCallbackDriver"));
       RemoveCallback();
       NextDriver()->SetGraphTime(this, mIterationStart, mIterationEnd);
@@ -1000,13 +1005,20 @@ AudioCallbackDriver::DataCallback(const AudioDataValue* aInputBuffer,
   mGraphImpl->NotifyOutputData(aOutputBuffer, static_cast<size_t>(aFrames),
                                mSampleRate, mOutputChannels);
 
+  if (!stillProcessing) {
+    // Enter shutdown mode. The stable-state handler will detect this
+    // and complete shutdown if the graph does not get restarted.
+    mGraphImpl->SignalMainThreadCleanup();
+    return aFrames - 1;
+  }
+
   bool switching = false;
   {
     MonitorAutoLock mon(mGraphImpl->GetMonitor());
     switching = !!NextDriver();
   }
 
-  if (switching && stillProcessing) {
+  if (switching) {
     // If the audio stream has not been started by the previous driver or
     // the graph itself, keep it alive.
     MonitorAutoLock mon(mGraphImpl->GetMonitor());
@@ -1023,11 +1035,6 @@ AudioCallbackDriver::DataCallback(const AudioDataValue* aInputBuffer,
     return aFrames - 1;
   }
 
-  if (!stillProcessing) {
-    LOG(LogLevel::Debug,
-        ("Stopping audio thread for MediaStreamGraph %p", this));
-    return aFrames - 1;
-  }
   return aFrames;
 }
 

dom/media/MediaStreamGraph.cpp

@@ -1217,11 +1217,13 @@ MediaStreamGraphImpl::PrepareUpdatesToMainThreadState(bool aFinalUpdate)
     }
   }
 
-  // Don't send the message to the main thread if it's not going to have
-  // any work to do.
-  if (aFinalUpdate ||
-      !mUpdateRunnables.IsEmpty() ||
-      !mStreamUpdates.IsEmpty()) {
+  // If this is the final update, then a stable state event will soon be
+  // posted just before this thread finishes, and so there is no need to also
+  // post here.
+  if (!aFinalUpdate &&
+      // Don't send the message to the main thread if it's not going to have
+      // any work to do.
+      !(mUpdateRunnables.IsEmpty() && mStreamUpdates.IsEmpty())) {
     EnsureStableStateEventPosted();
   }
 }
@@ -1460,12 +1462,7 @@ MediaStreamGraphImpl::UpdateMainThreadState()
     (IsEmpty() && mBackMessageQueue.IsEmpty());
   PrepareUpdatesToMainThreadState(finalUpdate);
   if (finalUpdate) {
-    // Enter shutdown mode. The stable-state handler will detect this
-    // and complete shutdown. Destroy any streams immediately.
-    LOG(LogLevel::Debug,
-        ("MediaStreamGraph %p waiting for main thread cleanup", this));
-    // We'll shut down this graph object if it does not get restarted.
-    LifecycleStateRef() = LIFECYCLE_WAITING_FOR_MAIN_THREAD_CLEANUP;
+    // Enter shutdown mode when this iteration is completed.
     // No need to Destroy streams here. The main-thread owner of each
     // stream is responsible for calling Destroy on them.
     return false;
@@ -1898,6 +1895,19 @@ MediaStreamGraphImpl::EnsureStableStateEventPosted()
   mAbstractMainThread->Dispatch(event.forget());
 }
 
+void
+MediaStreamGraphImpl::SignalMainThreadCleanup()
+{
+  MOZ_ASSERT(mDriver->OnThread());
+
+  MonitorAutoLock lock(mMonitor);
+  LOG(LogLevel::Debug,
+      ("MediaStreamGraph %p waiting for main thread cleanup", this));
+  LifecycleStateRef() =
+    MediaStreamGraphImpl::LIFECYCLE_WAITING_FOR_MAIN_THREAD_CLEANUP;
+  EnsureStableStateEventPosted();
+}
+
 void
 MediaStreamGraphImpl::AppendMessage(UniquePtr<ControlMessage> aMessage)
 {

dom/media/MediaStreamGraphImpl.h

@@ -198,6 +198,14 @@ public:
    */
   bool OneIteration(GraphTime aStateEnd);
 
+  /**
+   * Called from the driver, when the graph thread is about to stop, to tell
+   * the main thread to attempt to begin cleanup.  The main thread may either
+   * shutdown or revive the graph depending on whether it receives new
+   * messages.
+   */
+  void SignalMainThreadCleanup();
+
   bool Running() const
   {
     return LifecycleStateRef() == LIFECYCLE_RUNNING;
@@ -724,8 +732,9 @@ public:
   };
 
   /**
-   * Modified on the main and graph thread (in UpdateMainThreadState() when
-   * we're about to shutdown) in mMonitor. mMonitor must be held when accessed.
+   * Modified only in mMonitor.  Transitions to
+   * LIFECYCLE_WAITING_FOR_MAIN_THREAD_CLEANUP occur on the graph thread at
+   * the end of an iteration.  All other transitions occur on the main thread.
    */
   LifecycleState mLifecycleState;
   LifecycleState& LifecycleStateRef()