From 0f9c0d79c639edf5d561c11860025d3cfe868f18 Mon Sep 17 00:00:00 2001
From: Jean-Yves Avenard <jyavenard@mozilla.com>
Date: Thu, 9 Jul 2020 02:46:55 +0000
Subject: [PATCH] Bug 1649974 - P2. Use a TaskQueue with media threadpool for
 RemoteDecoderManagerParent. r=mattwoodrow

Sync dispatch are being used; due to how the background taskqueue is setup this could cause a hang if if also called from a background taskqueue.

Differential Revision: https://phabricator.services.mozilla.com/D82500
---
 dom/media/ipc/RemoteDecoderManagerParent.cpp | 41 ++++++++------------
 1 file changed, 16 insertions(+), 25 deletions(-)

diff --git a/dom/media/ipc/RemoteDecoderManagerParent.cpp b/dom/media/ipc/RemoteDecoderManagerParent.cpp
index ff5a9e990b10..638caa6caca2 100644
--- a/dom/media/ipc/RemoteDecoderManagerParent.cpp
+++ b/dom/media/ipc/RemoteDecoderManagerParent.cpp
@@ -9,14 +9,13 @@
 #  include <objbase.h>
 #endif
 
+#include "ImageContainer.h"
 #include "RemoteAudioDecoder.h"
 #include "RemoteVideoDecoder.h"
 #include "VideoUtils.h"  // for MediaThreadType
-
-#include "ImageContainer.h"
-#include "mozilla/layers/VideoBridgeChild.h"
-#include "mozilla/layers/ImageDataSerializer.h"
 #include "mozilla/SyncRunnable.h"
+#include "mozilla/layers/ImageDataSerializer.h"
+#include "mozilla/layers/VideoBridgeChild.h"
 
 namespace mozilla {
 
@@ -29,7 +28,7 @@ using namespace ipc;
 using namespace layers;
 using namespace gfx;
 
-StaticRefPtr<nsISerialEventTarget> sRemoteDecoderManagerParentThread;
+StaticRefPtr<TaskQueue> sRemoteDecoderManagerParentThread;
 
 SurfaceDescriptorGPUVideo RemoteDecoderManagerParent::StoreImage(
     Image* aImage, TextureClient* aTexture) {
@@ -72,19 +71,13 @@ bool RemoteDecoderManagerParent::StartupThreads() {
     return false;
   }
 
-  nsCOMPtr<nsISerialEventTarget> managerThread;
-  nsresult rv = NS_CreateBackgroundTaskQueue("RemVidParent",
-                                             getter_AddRefs(managerThread));
-  if (NS_FAILED(rv)) {
-    return false;
-  }
-  sRemoteDecoderManagerParentThread = managerThread;
+  sRemoteDecoderManagerParentThread = new TaskQueue(
+      GetMediaThreadPool(MediaThreadType::PLAYBACK), "RemVidParent");
   if (XRE_IsGPUProcess()) {
-    sRemoteDecoderManagerParentThread->Dispatch(
-        NS_NewRunnableFunction(
+    MOZ_ALWAYS_SUCCEEDS(
+        sRemoteDecoderManagerParentThread->Dispatch(NS_NewRunnableFunction(
             "RemoteDecoderManagerParent::StartupThreads",
-            []() { layers::VideoBridgeChild::StartupForGPUProcess(); }),
-        NS_DISPATCH_NORMAL);
+            []() { layers::VideoBridgeChild::StartupForGPUProcess(); })));
   }
 
   auto* obs = new RemoteDecoderManagerThreadShutdownObserver();
@@ -93,16 +86,14 @@ bool RemoteDecoderManagerParent::StartupThreads() {
 }
 
 void RemoteDecoderManagerParent::ShutdownThreads() {
+  sRemoteDecoderManagerParentThread->BeginShutdown();
+  sRemoteDecoderManagerParentThread->AwaitShutdownAndIdle();
   sRemoteDecoderManagerParentThread = nullptr;
 }
 
+/* static */
 void RemoteDecoderManagerParent::ShutdownVideoBridge() {
   if (sRemoteDecoderManagerParentThread) {
-    if (sRemoteDecoderManagerParentThread->IsOnCurrentThread()) {
-      VideoBridgeChild::Shutdown();
-      return;
-    }
-
     RefPtr<Runnable> task = NS_NewRunnableFunction(
         "RemoteDecoderManagerParent::ShutdownVideoBridge",
         []() { VideoBridgeChild::Shutdown(); });
@@ -131,8 +122,8 @@ bool RemoteDecoderManagerParent::CreateForContent(
       NewRunnableMethod<Endpoint<PRemoteDecoderManagerParent>&&>(
           "dom::RemoteDecoderManagerParent::Open", parent,
           &RemoteDecoderManagerParent::Open, std::move(aEndpoint));
-  sRemoteDecoderManagerParentThread->Dispatch(task.forget(),
-                                              NS_DISPATCH_NORMAL);
+  MOZ_ALWAYS_SUCCEEDS(
+      sRemoteDecoderManagerParentThread->Dispatch(task.forget()));
   return true;
 }
 
@@ -150,8 +141,8 @@ bool RemoteDecoderManagerParent::CreateVideoBridgeToOtherProcess(
   RefPtr<Runnable> task =
       NewRunnableFunction("gfx::VideoBridgeChild::Open",
                           &VideoBridgeChild::Open, std::move(aEndpoint));
-  sRemoteDecoderManagerParentThread->Dispatch(task.forget(),
-                                              NS_DISPATCH_NORMAL);
+  MOZ_ALWAYS_SUCCEEDS(
+      sRemoteDecoderManagerParentThread->Dispatch(task.forget()));
   return true;
 }