WorkerThread should not start execution if WorkerThread::stop is already called

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 222 matching lines @@
     MutexLocker locker(m_workerInspectorControllerMutex);
     if (m_workerInspectorController)
         m_workerInspectorController->interruptAndDispatchInspectorCommands();
 }
 
 void WorkerThread::initialize()
 {
     KURL scriptURL = m_startupData->m_scriptURL;
     String sourceCode = m_startupData->m_sourceCode;
     WorkerThreadStartMode startMode = m_startupData->m_startMode;
-    m_microtaskRunner = adoptPtr(new MicrotaskRunner);
-    m_thread->addTaskObserver(m_microtaskRunner.get());

[horo, 2014/08/13 03:32:29]

Why do you remove these lines?

[haraken, 2014/08/13 04:13:42]

These lines are moved to after the 'if(m_terminated)' check. If the thread is
already stopped, we don't want to create a microtask runner.

 
     {
         MutexLocker lock(m_threadCreationMutex);
 
+        if (m_terminated) // The worker was terminated before the thread had a chance to run.
+            return;
+
+        m_microtaskRunner = adoptPtr(new MicrotaskRunner);
+        m_thread->addTaskObserver(m_microtaskRunner.get());
         m_pendingGCRunner = adoptPtr(new PendingGCRunner);
         m_messageLoopInterruptor = adoptPtr(new MessageLoopInterruptor(m_thread.get()));
         m_thread->addTaskObserver(m_pendingGCRunner.get());
         ThreadState::attach();
         ThreadState::current()->addInterruptor(m_messageLoopInterruptor.get());
         m_workerGlobalScope = createWorkerGlobalScope(m_startupData.release());
 
         m_sharedTimer = adoptPtr(new WorkerSharedTimer(this));
         PlatformThreadData::current().threadTimers().setSharedTimer(m_sharedTimer.get());
-
-        if (m_terminated) {
-            // The worker was terminated before the thread had a chance to run. Since the context didn't exist yet,
-            // forbidExecution() couldn't be called from stop().
-            m_workerGlobalScope->script()->forbidExecution();
-        }
     }
 
     // The corresponding call to didStopWorkerRunLoop is in
     // ~WorkerScriptController.
     blink::Platform::current()->didStartWorkerRunLoop(blink::WebWorkerRunLoop(this));
 
     // Notify proxy that a new WorkerGlobalScope has been created and started.
     m_workerReportingProxy.workerGlobalScopeStarted(m_workerGlobalScope.get());
 
     WorkerScriptController* script = m_workerGlobalScope->script();
@@ skipping 97 matching lines @@
 {
     // Prevent the deadlock between GC and an attempt to stop a thread.
     ThreadState::SafePointScope safePointScope(ThreadState::HeapPointersOnStack);
 
     // Protect against this method and initialize() racing each other.
     MutexLocker lock(m_threadCreationMutex);
 
     // If stop has already been called, just return.
     if (m_terminated)
         return;
+    m_terminated = true;
 
     // Signal the thread to notify that the thread's stopping.
     if (m_shutdownEvent)
         m_shutdownEvent->signal();
 
     if (!m_workerGlobalScope)
         return;
 
     // Ensure that tasks are being handled by thread event loop. If script execution weren't forbidden, a while(1) loop in JS could keep the thread alive forever.
     m_workerGlobalScope->script()->scheduleExecutionTermination();
     m_workerGlobalScope->wasRequestedToTerminate();
     InspectorInstrumentation::didKillAllExecutionContextTasks(m_workerGlobalScope.get());
     m_debuggerMessageQueue.kill();
     postTask(WorkerThreadShutdownStartTask::create());
-    m_terminated = true;
 }
 
 bool WorkerThread::isCurrentThread() const
 {
     return m_thread && m_thread->isCurrentThread();
 }
 
 void WorkerThread::idleHandler()
 {
     ASSERT(m_workerGlobalScope.get());
@@ skipping 58 matching lines @@
     InspectorInstrumentation::didLeaveNestedRunLoop(m_workerGlobalScope.get());
 }
 
 void WorkerThread::setWorkerInspectorController(WorkerInspectorController* workerInspectorController)
 {
     MutexLocker locker(m_workerInspectorControllerMutex);
     m_workerInspectorController = workerInspectorController;
 }
 
 } // namespace blink