Introduce WorkerBackingThread

third_party/WebKit/Source/core/workers/WorkerThread.cpp

 /*
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  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
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  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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 #include "core/workers/WorkerThread.h"
 
 #include "bindings/core/v8/ScriptSourceCode.h"
-#include "bindings/core/v8/V8GCController.h"
-#include "bindings/core/v8/V8IdleTaskRunner.h"
-#include "bindings/core/v8/V8Initializer.h"
 #include "core/dom/Microtask.h"
 #include "core/inspector/InspectorInstrumentation.h"
 #include "core/inspector/WorkerInspectorController.h"
 #include "core/workers/DedicatedWorkerGlobalScope.h"
+#include "core/workers/WorkerBackingThread.h"
 #include "core/workers/WorkerClients.h"
 #include "core/workers/WorkerReportingProxy.h"
 #include "core/workers/WorkerThreadStartupData.h"
 #include "platform/ThreadSafeFunctional.h"
 #include "platform/WaitableEvent.h"
 #include "platform/heap/SafePoint.h"
 #include "platform/heap/ThreadState.h"
 #include "platform/weborigin/KURL.h"
-#include "public/platform/Platform.h"
 #include "public/platform/WebScheduler.h"
 #include "public/platform/WebThread.h"
 #include "wtf/Functional.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/WeakPtr.h"
 #include "wtf/text/WTFString.h"
 #include <limits.h>
 
 namespace blink {
 
@@ skipping 131 matching lines @@
 
     static double infiniteTime() { return std::numeric_limits<double>::max(); }
 
 private:
     Mutex m_mutex;
     ThreadCondition m_condition;
     Deque<OwnPtr<Task>> m_queue;
     bool m_killed = false;
 };
 
-WorkerThread::WorkerThread(PassRefPtr<WorkerLoaderProxy> workerLoaderProxy, WorkerReportingProxy& workerReportingProxy)
+WorkerThread::WorkerThread(PassRefPtr<WorkerLoaderProxy> workerLoaderProxy, WorkerReportingProxy& workerReportingProxy, PassRefPtr<WorkerBackingThread> thread)
     : m_started(false)
     , m_terminated(false)
     , m_shutdown(false)
     , m_debuggerTaskQueue(adoptPtr(new DebuggerTaskQueue))
     , m_workerLoaderProxy(workerLoaderProxy)
     , m_workerReportingProxy(workerReportingProxy)
     , m_webScheduler(nullptr)
-    , m_isolate(nullptr)
+    , m_workerBackingThread(thread)
     , m_shutdownEvent(adoptPtr(new WaitableEvent(
         WaitableEvent::ResetPolicy::Manual,
         WaitableEvent::InitialState::NonSignaled)))
     , m_terminationEvent(adoptPtr(new WaitableEvent(
         WaitableEvent::ResetPolicy::Manual,
         WaitableEvent::InitialState::NonSignaled)))
 {
     MutexLocker lock(threadSetMutex());
     workerThreads().add(this);
 }
@@ skipping 45 matching lines @@
         // The worker was terminated before the thread had a chance to run.
         if (m_terminated) {
             // Notify the proxy that the WorkerGlobalScope has been disposed of.
             // This can free this thread object, hence it must not be touched afterwards.
             m_workerReportingProxy.workerThreadTerminated();
             // Notify the main thread that it is safe to deallocate our resources.
             m_terminationEvent->signal();
             return;
         }
 
+        m_workerBackingThread->attach();
+
         m_microtaskRunner = adoptPtr(new WorkerMicrotaskRunner(this));
-        initializeBackingThread();
         backingThread().addTaskObserver(m_microtaskRunner.get());
 
-        m_isolate = initializeIsolate();
         // Optimize for memory usage instead of latency for the worker isolate.
-        m_isolate->IsolateInBackgroundNotification();
+        isolate()->IsolateInBackgroundNotification();
         m_workerGlobalScope = createWorkerGlobalScope(startupData);
         m_workerGlobalScope->scriptLoaded(sourceCode.length(), cachedMetaData.get() ? cachedMetaData->size() : 0);
 
-        didStartWorkerThread();
-
         // Notify proxy that a new WorkerGlobalScope has been created and started.
         m_workerReportingProxy.workerGlobalScopeStarted(m_workerGlobalScope.get());
 
         WorkerOrWorkletScriptController* scriptController = m_workerGlobalScope->scriptController();
         if (!scriptController->isExecutionForbidden())
             scriptController->initializeContextIfNeeded();
     }
     m_workerGlobalScope->workerInspectorController()->workerContextInitialized(startMode == PauseWorkerGlobalScopeOnStart);
 
     if (m_workerGlobalScope->scriptController()->isContextInitialized()) {
@@ skipping 16 matching lines @@
         if (m_shutdown)
             return;
         m_shutdown = true;
     }
 
     // This should be called before we start the shutdown procedure.
     workerReportingProxy().willDestroyWorkerGlobalScope();
 
     workerGlobalScope()->dispose();
 
-    // This should be called after the WorkerGlobalScope's disposed (which may
-    // trigger some last-minutes cleanups) and before the thread actually stops.
-    willStopWorkerThread();
-
     backingThread().removeTaskObserver(m_microtaskRunner.get());
     postTask(BLINK_FROM_HERE, createSameThreadTask(&WorkerThread::performShutdownTask, this));
 }
 
 void WorkerThread::performShutdownTask()
 {
     // The below assignment will destroy the context, which will in turn notify messaging proxy.
     // We cannot let any objects survive past thread exit, because no other thread will run GC or otherwise destroy them.
     // If Oilpan is enabled, we detach of the context/global scope, with the final heap cleanup below sweeping it out.
 #if !ENABLE(OILPAN)
     ASSERT(m_workerGlobalScope->hasOneRef());
 #endif
     m_workerGlobalScope->notifyContextDestroyed();
     m_workerGlobalScope = nullptr;
 
-    willDestroyIsolate();
-    shutdownBackingThread();
-    destroyIsolate();
-    m_isolate = nullptr;
-
+    m_workerBackingThread->detach();
+    m_workerBackingThread = nullptr;
     m_microtaskRunner = nullptr;
 
     // Notify the proxy that the WorkerGlobalScope has been disposed of.
     // This can free this thread object, hence it must not be touched afterwards.
     workerReportingProxy().workerThreadTerminated();
 
     m_terminationEvent->signal();
 }
 
 void WorkerThread::terminate()
@@ skipping 42 matching lines @@
         return;
 
     // If the worker thread was never initialized, don't start another
     // shutdown, but still wait for the thread to signal when termination has
     // completed.
     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->scriptController()->willScheduleExecutionTermination();
-    terminateV8Execution();
+
+    if (1 == m_workerBackingThread->workerScriptCount()) {
+        // This condition is not entirely correct because other scripts
+        // can be being initialized or terminated simuletaneously. Though this
+        // function itself is protected by a mutex, it is possible that
+        // |workerScriptCount()| here is not consistent with that in
+        // |initialize| and |shutdown|.
+        isolate()->TerminateExecution();
+    }

[kinuko, 2016/02/29 09:32:53]

The comment just leaves readers unsure if this code is right or not...
initialize() sequence looks ok to me as attach won't be called once we pass this
part?  While it looks it's possible that we don't take this branch but
shutdown() is called on worker thread, but it should be fine too as we don't
need to worry about terminating v8 execution.  Are there other cases we need to
take care?

Also: it doesn't feel WorkerBackingThread should expose this detail here, would
we be able to move this part hidden in WorkerBackingThread?

[yhirano, 2016/02/29 23:47:32]

Imagine there are two WorkerThread x and y attached to a WorkerBackingThread and
we want to shutdown both.

-----
Call x->terminate() on the main thread.
Call y->terminate() on the main thread.
-----

It is possible that y->terminate() runs on the main thread before x->shutdown()
on the worker thread. In this case, TerminateExecution will never be called.
It's problematic if the worker backing loop runs an infinite JS loop: we cannot
terminate the worker backing thread. Moreover, if we call terminateAndWait on
the main thread, it blocks the main thread too.

[yhirano, 2016/03/01 00:04:52]

Correction:
 before x->shutdown() on the worker thread. => before x->shutdown() runs on the
worker thread.
 if the worker backing loop runs => if the worker backing thread runs

 
     InspectorInstrumentation::didKillAllExecutionContextTasks(m_workerGlobalScope.get());
     m_debuggerTaskQueue->kill();
     backingThread().postTask(BLINK_FROM_HERE, threadSafeBind(&WorkerThread::shutdown, AllowCrossThreadAccess(this)));
 }
 
-void WorkerThread::didStartWorkerThread()
+WorkerBackingThread& WorkerThread::workerBackingThread()
 {
-    ASSERT(isCurrentThread());
-    Platform::current()->didStartWorkerThread();
+    ASSERT(m_workerBackingThread);
+    return *m_workerBackingThread;
 }
 
-void WorkerThread::willStopWorkerThread()
+WebThreadSupportingGC& WorkerThread::backingThread()
 {
-    ASSERT(isCurrentThread());
-    Platform::current()->willStopWorkerThread();
+    ASSERT(m_workerBackingThread);
+    return m_workerBackingThread->backingThread();
+}
+
+v8::Isolate* WorkerThread::isolate() const
+{
+    return m_workerBackingThread->isolate();
 }
 
 void WorkerThread::terminateAndWaitForAllWorkers()
 {
     // Keep this lock to prevent WorkerThread instances from being destroyed.
     MutexLocker lock(threadSetMutex());
     HashSet<WorkerThread*> threads = workerThreads();
     for (WorkerThread* thread : threads)
         thread->terminateInternal();
 
     for (WorkerThread* thread : threads)
         thread->m_terminationEvent->wait();
 }
 
 bool WorkerThread::isCurrentThread()
 {
     return m_started && backingThread().isCurrentThread();
 }
 
 void WorkerThread::postTask(const WebTraceLocation& location, PassOwnPtr<ExecutionContextTask> task)
 {
     backingThread().postTask(location, createWorkerThreadTask(task, true));
 }
 
 void WorkerThread::postDelayedTask(const WebTraceLocation& location, PassOwnPtr<ExecutionContextTask> task, long long delayMs)
 {
     backingThread().postDelayedTask(location, createWorkerThreadTask(task, true), delayMs);
 }
 
-void WorkerThread::initializeBackingThread()
-{
-    ASSERT(isCurrentThread());
-    backingThread().initialize();
-}
-
-void WorkerThread::shutdownBackingThread()
-{
-    ASSERT(isCurrentThread());
-    backingThread().shutdown();
-}
-
-v8::Isolate* WorkerThread::initializeIsolate()
-{
-    ASSERT(isCurrentThread());
-    ASSERT(!m_isolate);
-    v8::Isolate* isolate = V8PerIsolateData::initialize();
-    V8Initializer::initializeWorker(isolate);
-
-    OwnPtr<V8IsolateInterruptor> interruptor = adoptPtr(new V8IsolateInterruptor(isolate));
-    ThreadState::current()->addInterruptor(interruptor.release());
-    ThreadState::current()->registerTraceDOMWrappers(isolate, V8GCController::traceDOMWrappers);
-    if (RuntimeEnabledFeatures::v8IdleTasksEnabled())
-        V8PerIsolateData::enableIdleTasks(isolate, adoptPtr(new V8IdleTaskRunner(m_webScheduler)));
-    return isolate;
-}
-
-void WorkerThread::willDestroyIsolate()
-{
-    ASSERT(isCurrentThread());
-    ASSERT(m_isolate);
-    V8PerIsolateData::willBeDestroyed(m_isolate);
-}
-
-void WorkerThread::destroyIsolate()
-{
-    ASSERT(isCurrentThread());
-    V8PerIsolateData::destroy(m_isolate);
-}
-
-void WorkerThread::terminateV8Execution()
-{
-    ASSERT(isMainThread());
-    m_isolate->TerminateExecution();
-}
-
 void WorkerThread::appendDebuggerTask(PassOwnPtr<Closure> task)
 {
     {
         MutexLocker lock(m_threadStateMutex);
         if (m_shutdown)
             return;
     }
     m_debuggerTaskQueue->append(task);
 }
 
@@ skipping 29 matching lines @@
     InspectorInstrumentation::didLeaveNestedRunLoop(m_workerGlobalScope.get());
 }
 
 void WorkerThread::setWorkerInspectorController(WorkerInspectorController* workerInspectorController)
 {
     MutexLocker locker(m_workerInspectorControllerMutex);
     m_workerInspectorController = workerInspectorController;
 }
 
 } // namespace blink