Bug 1316506 - Make RemoteVideoDecoder::Flush synchronous. r=billm

--HG--
extra : rebase_source : 1e0b6991a629de72248ac80dd64c30126d0c10fd

dom/media/ipc/PVideoDecoder.ipdl

@@ -62,6 +62,8 @@ child:
   async InitComplete(bool hardware, nsCString hardwareReason);
   async InitFailed(nsresult reason);
 
+  async FlushComplete();
+
   // Each output includes a SurfaceDescriptorGPUVideo that represents the decoded
   // frame. This SurfaceDescriptor can be used on the Layers IPDL protocol, but
   // must be released explicitly using DeallocateSurfaceDescriptorGPUVideo

dom/media/ipc/RemoteVideoDecoder.cpp

@@ -75,11 +75,12 @@ void
 RemoteVideoDecoder::Flush()
 {
   MOZ_ASSERT(mCallback->OnReaderTaskQueue());
-  RefPtr<RemoteVideoDecoder> self = this;
-  VideoDecoderManagerChild::GetManagerThread()->Dispatch(NS_NewRunnableFunction([self]() {
-    MOZ_ASSERT(self->mActor);
-    self->mActor->Flush();
+  SynchronousTask task("Decoder flush");
+  VideoDecoderManagerChild::GetManagerThread()->Dispatch(NS_NewRunnableFunction([&]() {
+    MOZ_ASSERT(this->mActor);
+    this->mActor->Flush(&task);
   }), NS_DISPATCH_NORMAL);
+  task.Wait();
 }
 
 void

dom/media/ipc/VideoDecoderChild.cpp

@@ -10,6 +10,7 @@
 #include "MediaInfo.h"
 #include "ImageContainer.h"
 #include "GPUVideoImage.h"
+#include "mozilla/layers/SynchronousTask.h"
 
 namespace mozilla {
 namespace dom {
@@ -107,6 +108,15 @@ VideoDecoderChild::RecvInitFailed(const nsresult& aReason)
   return IPC_OK();
 }
 
+mozilla::ipc::IPCResult
+VideoDecoderChild::RecvFlushComplete()
+{
+  MOZ_ASSERT(mFlushTask);
+  AutoCompleteTask complete(mFlushTask);
+  mFlushTask = nullptr;
+  return IPC_OK();
+}
+
 void
 VideoDecoderChild::ActorDestroy(ActorDestroyReason aWhy)
 {
@@ -122,6 +132,10 @@ VideoDecoderChild::ActorDestroy(ActorDestroyReason aWhy)
       }
     }));
   }
+  if (mFlushTask) {
+    AutoCompleteTask complete(mFlushTask);
+    mFlushTask = nullptr;
+  }
   mCanSend = false;
 }
 
@@ -212,11 +226,14 @@ VideoDecoderChild::Input(MediaRawData* aSample)
 }
 
 void
-VideoDecoderChild::Flush()
+VideoDecoderChild::Flush(SynchronousTask* aTask)
 {
   AssertOnManagerThread();
   if (mCanSend) {
     SendFlush();
+    mFlushTask = aTask;
+  } else {
+    AutoCompleteTask complete(aTask);
   }
 }
 

dom/media/ipc/VideoDecoderChild.h

@@ -12,6 +12,9 @@
 #include "PlatformDecoderModule.h"
 
 namespace mozilla {
+namespace layers {
+class SynchronousTask;
+}
 namespace dom {
 
 class RemoteVideoDecoder;
@@ -32,12 +35,13 @@ public:
   mozilla::ipc::IPCResult RecvError(const nsresult& aError) override;
   mozilla::ipc::IPCResult RecvInitComplete(const bool& aHardware, const nsCString& aHardwareReason) override;
   mozilla::ipc::IPCResult RecvInitFailed(const nsresult& aReason) override;
+  mozilla::ipc::IPCResult RecvFlushComplete() override;
 
   void ActorDestroy(ActorDestroyReason aWhy) override;
 
   RefPtr<MediaDataDecoder::InitPromise> Init();
   void Input(MediaRawData* aSample);
-  void Flush();
+  void Flush(layers::SynchronousTask* Task);
   void Drain();
   void Shutdown();
   bool IsHardwareAccelerated(nsACString& aFailureReason) const;
@@ -66,6 +70,8 @@ private:
 
   MozPromiseHolder<MediaDataDecoder::InitPromise> mInitPromise;
 
+  layers::SynchronousTask* mFlushTask;
+
   nsCString mHardwareAcceleratedReason;
   bool mCanSend;
   bool mInitialized;

dom/media/ipc/VideoDecoderParent.cpp

@@ -141,6 +141,16 @@ VideoDecoderParent::RecvFlush()
   if (mDecoder) {
     mDecoder->Flush();
   }
+
+  // Dispatch a runnable to our own event queue so that
+  // it will be processed after anything that got dispatched
+  // during the Flush call.
+  RefPtr<VideoDecoderParent> self = this;
+  mManagerTaskQueue->Dispatch(NS_NewRunnableFunction([self]() {
+    if (!self->mDestroyed) {
+      Unused << self->SendFlushComplete();
+    }
+  }));
   return IPC_OK();
 }