Ensures that audio tasks cannot run after AudioManager is deleted.

content/browser/browser_main_loop.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/browser_main_loop.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 75 matching lines @@
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/tracing_controller.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_features.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/main_function_params.h"
 #include "content/public/common/result_codes.h"
 #include "device/battery/battery_status_service.h"
 #include "device/gamepad/gamepad_service.h"
 #include "gpu/vulkan/features.h"
+#include "media/audio/audio_manager.h"
 #include "media/audio/audio_system_impl.h"
 #include "media/base/media.h"
 #include "media/base/user_input_monitor.h"
 #include "media/midi/midi_service.h"
 #include "mojo/edk/embedder/embedder.h"
 #include "mojo/edk/embedder/scoped_ipc_support.h"
 #include "net/base/network_change_notifier.h"
 #include "net/socket/client_socket_factory.h"
 #include "net/ssl/ssl_config_service.h"
 #include "ppapi/features/features.h"
@@ skipping 1280 matching lines @@
 #if !defined(OS_ANDROID)
   {
     TRACE_EVENT0("shutdown", "BrowserMainLoop::Subsystem:BatteryStatusService");
     device::BatteryStatusService::GetInstance()->Shutdown();
   }
 #endif
   {
     TRACE_EVENT0("shutdown", "BrowserMainLoop::Subsystem:DeleteDataSources");
     URLDataManager::DeleteDataSources();
   }
+  {
+    TRACE_EVENT0("shutdown", "BrowserMainLoop::Subsystem:AudioMan");
+    DestroyAudioManager();
+  }
 
   if (parts_) {
     TRACE_EVENT0("shutdown", "BrowserMainLoop::Subsystem:PostDestroyThreads");
     parts_->PostDestroyThreads();
   }
 }
 
 void BrowserMainLoop::StopStartupTracingTimer() {
   startup_trace_timer_.Stop();
 }
@@ skipping 368 matching lines @@
   TracingController::GetInstance()->StopTracing(
       TracingController::CreateFileSink(
           startup_trace_file_,
           base::Bind(OnStoppedStartupTracing, startup_trace_file_)));
 }
 
 void BrowserMainLoop::CreateAudioManager() {
   DCHECK(!audio_thread_);
   DCHECK(!audio_manager_);
 
+  audio_thread_ = base::MakeUnique<AudioManagerThread>();
   audio_manager_ = GetContentClient()->browser()->CreateAudioManager(
+      audio_thread_->task_runner(), audio_thread_->worker_task_runner(),
       MediaInternals::GetInstance());
   if (!audio_manager_) {
-    audio_thread_ = base::MakeUnique<AudioManagerThread>();
     audio_manager_ = media::AudioManager::Create(
         audio_thread_->task_runner(), audio_thread_->worker_task_runner(),
         BrowserThread::GetTaskRunnerForThread(BrowserThread::FILE),
         MediaInternals::GetInstance());
   }
   CHECK(audio_manager_);
 
   audio_system_ = media::AudioSystemImpl::Create(audio_manager_.get());
   CHECK(audio_system_);
 }
 
+void BrowserMainLoop::DestroyAudioManager() {
+  DCHECK(audio_manager_);
+  DCHECK(audio_thread_);
+
+  // |audio_manager_| must be shut down on |audio_thread_| before it is deleted.
+  if (audio_manager_->GetTaskRunner()->BelongsToCurrentThread()) {
+    audio_manager_->Shutdown();
+  } else {
+    audio_manager_->GetTaskRunner()->PostTask(
+        FROM_HERE, base::Bind(&media::AudioManager::Shutdown,
+                              base::Unretained(audio_manager_.get())));
+  }
+
+  // Stop |audio_thread_| before deleting |audio_manager_| so that all tasks
+  // currently in the |audio_thread_| queue run and no more can be posted.
+  audio_thread_.reset();

[o1ka, 2017/03/28 18:32:23]

Is there a guarantee that all the queued tasks will run? (Sorry cannot look it
up now - I'm on the go)

[o1ka, 2017/03/29 09:28:32]

Never mind - I checked it now, base::Thread will do it :)

+
+  // Safe to delete the |audio_manager_|.
+  audio_manager_.reset();

[o1ka, 2017/03/28 18:32:23]

Looks like we need to reset AudioSystem before this?

+}
+
 }  // namespace content