ServiceWorker: Fix data race in shutdown sequence

Source/core/workers/WorkerThread.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 385 matching lines @@
         workerGlobalScope->removeAllEventListeners();
 
         // Stick a shutdown command at the end of the queue, so that we deal
         // with all the cleanup tasks the databases post first.
         workerGlobalScope->postTask(WorkerThreadShutdownFinishTask::create());
     }
 
     virtual bool isCleanupTask() const { return true; }
 };
 
 void WorkerThread::stop()

[haraken, 2014/10/30 05:12:13]

Nit: We might want to rename "stop" to "terminate" in a follow-up CL.

 {
     // Prevent the deadlock between GC and an attempt to stop a thread.
     ThreadState::SafePointScope safePointScope(ThreadState::HeapPointersOnStack);
     stopInternal();
 }
 
 void WorkerThread::stopInShutdownSequence()
 {
     stopInternal();
 }
 
+void WorkerThread::terminateAndWait()
+{
+    stop();

[horo, 2014/10/30 08:14:47]

I think we don't need to call stop() from the destructor of
WebEmbeddedWorkerImpl.

WebEmbeddedWorkerImpl is deleted after
ServiceWorkerGlobalScopeProxy::workerThreadTerminated() is called.
So when deleting WebEmbeddedWorkerImpl, m_workerThread->terminated() must be
true.

Adding "ASSERT(m_workerThread->terminated())" in the destructor of
WebEmbeddedWorkerImpl is better.

[Kunihiko Sakamoto, 2014/10/30 08:31:29]

Done.

+    terminationEvent()->wait();
+}
+
 bool WorkerThread::terminated()
 {
     MutexLocker lock(m_threadCreationMutex);
     return m_terminated;
 }
 
 void WorkerThread::stopInternal()
 {
     // Protect against this method and initialize() racing each other.
     MutexLocker lock(m_threadCreationMutex);
@@ skipping 98 matching lines @@
     InspectorInstrumentation::didLeaveNestedRunLoop(m_workerGlobalScope.get());
 }
 
 void WorkerThread::setWorkerInspectorController(WorkerInspectorController* workerInspectorController)
 {
     MutexLocker locker(m_workerInspectorControllerMutex);
     m_workerInspectorController = workerInspectorController;
 }
 
 } // namespace blink