[Blink-Worker] WorkerThread fires idleHandler only at the end of processing all tasks.

Source/core/workers/WorkerThread.cpp

Index: Source/core/workers/WorkerThread.cpp
diff --git a/Source/core/workers/WorkerThread.cpp b/Source/core/workers/WorkerThread.cpp
index 4afc1f86c0dd84d85880c9f0ca1d31ee3f73c104..2f93068f30f1ab643c47c5a1ff4087362f41f7bb 100644
--- a/Source/core/workers/WorkerThread.cpp
+++ b/Source/core/workers/WorkerThread.cpp
@@ -180,48 +180,50 @@ private:
     WorkerThreadCancelableTask* m_lastQueuedTask;
 };
 
-class WorkerThreadTask : public blink::WebThread::Task {
-    WTF_MAKE_NONCOPYABLE(WorkerThreadTask); WTF_MAKE_FAST_ALLOCATED;
-public:
-    static PassOwnPtr<WorkerThreadTask> create(WorkerThread& workerThread, PassOwnPtr<ExecutionContextTask> task, bool isInstrumented)
-    {
-        return adoptPtr(new WorkerThreadTask(workerThread, task, isInstrumented));
-    }
-
-    virtual ~WorkerThreadTask() { }
+// WorkerThreadTask made private to WorkerThread
+PassOwnPtr<WorkerThread::WorkerThreadTask> WorkerThread::WorkerThreadTask::create(WorkerThread& workerThread
+    , PassOwnPtr<ExecutionContextTask> task, bool isInstrumented)
+{
+    return adoptPtr(new WorkerThreadTask(workerThread, task, isInstrumented));
+}
 
-    virtual void run() override
-    {
-        WorkerGlobalScope* workerGlobalScope = m_workerThread.workerGlobalScope();
-        // Tasks could be put on the message loop after the cleanup task,
-        // ensure none of those are ran.
-        if (!workerGlobalScope)
-            return;
+void WorkerThread::WorkerThreadTask::run()
+{
+    WorkerGlobalScope* workerGlobalScope = m_workerThread.workerGlobalScope();
+    // Tasks could be put on the message loop after the cleanup task,
+    // ensure none of those are ran.
+    if (!workerGlobalScope || m_isTaskCanceled)
+        return;
 
-        if (m_isInstrumented)
-            InspectorInstrumentation::willPerformExecutionContextTask(workerGlobalScope, m_task.get());
-        if ((!workerGlobalScope->isClosing() && !m_workerThread.terminated()) || m_task->isCleanupTask())
+    if (m_isInstrumented)
+        InspectorInstrumentation::willPerformExecutionContextTask(workerGlobalScope, m_task.get());
+    if ((!workerGlobalScope->isClosing() && !m_workerThread.terminated()) || m_task->isCleanupTask()) {
+        if (!m_isIdleHandlerTask || (m_isIdleHandlerTask && !m_workerThread.taskCount()))
             m_task->performTask(workerGlobalScope);
-        if (m_isInstrumented)
-            InspectorInstrumentation::didPerformExecutionContextTask(workerGlobalScope);
     }
+    if (m_isInstrumented)
+        InspectorInstrumentation::didPerformExecutionContextTask(workerGlobalScope);
 
-private:
-    WorkerThreadTask(WorkerThread& workerThread, PassOwnPtr<ExecutionContextTask> task, bool isInstrumented)
-        : m_workerThread(workerThread)
-        , m_task(task)
-        , m_isInstrumented(isInstrumented)
-    {
-        if (m_isInstrumented)
-            m_isInstrumented = !m_task->taskNameForInstrumentation().isEmpty();
-        if (m_isInstrumented)
-            InspectorInstrumentation::didPostExecutionContextTask(m_workerThread.workerGlobalScope(), m_task.get());
-    }
+    // If no more tasks are queued up after this, then queue up the idleHandler
+    // to trigger GC.
+    if (!m_isIdleHandlerTask && !m_workerThread.decrementAndReturnTaskCount() && !m_workerThread.m_lastQueuedIdleHandlerTask)
+        m_workerThread.queueUpIdleHandlerNow(kLongIdleHandlerDelayMs);
+}
 
-    WorkerThread& m_workerThread;
-    OwnPtr<ExecutionContextTask> m_task;
-    bool m_isInstrumented;
-};
+WorkerThread::WorkerThreadTask::WorkerThreadTask(WorkerThread& workerThread
+    , PassOwnPtr<ExecutionContextTask> task, bool isInstrumented)
+    : m_workerThread(workerThread)
+    , m_task(task)
+    , m_isInstrumented(isInstrumented)
+    , m_isIdleHandlerTask(false)
+    , m_isTaskCanceled(false)
+    , m_timeStamp(currentTime())
+{
+    if (m_isInstrumented)
+        m_isInstrumented = !m_task->taskNameForInstrumentation().isEmpty();
+    if (m_isInstrumented)
+        InspectorInstrumentation::didPostExecutionContextTask(m_workerThread.workerGlobalScope(), m_task.get());
+}
 
 class RunDebuggerQueueTask final : public ExecutionContextTask {
 public:
@@ -248,6 +250,8 @@ WorkerThread::WorkerThread(WorkerLoaderProxy& workerLoaderProxy, WorkerReporting
     , m_startupData(startupData)
     , m_shutdownEvent(adoptPtr(blink::Platform::current()->createWaitableEvent()))
     , m_terminationEvent(adoptPtr(blink::Platform::current()->createWaitableEvent()))
+    , m_lastQueuedIdleHandlerTask(nullptr)
+    , m_tasksCount(0)
 {
     MutexLocker lock(threadSetMutex());
     workerThreads().add(this);
@@ -330,7 +334,6 @@ void WorkerThread::initialize()
 
 void WorkerThread::cleanup()
 {
-
     // This should be called before we start the shutdown procedure.
     workerReportingProxy().willDestroyWorkerGlobalScope();
 
@@ -462,29 +465,80 @@ bool WorkerThread::isCurrentThread() const
     return m_thread && m_thread->isCurrentThread();
 }
 
+void WorkerThread::queueUpIdleHandlerNow(long long delayMs)
+{
+    OwnPtr<WorkerThreadTask> idleHandlerTask = WorkerThreadTask::create(*this, createSameThreadTask(&WorkerThread::idleHandler, this), true);
+
+    idleHandlerTask->setIsIdleHandlerTask(true);
+
+    if (clearIdleHandlerTaskIfSet()) {
+        WorkerThreadTask* tmp = idleHandlerTask.get();
+        m_thread->postDelayedTask(idleHandlerTask.leakPtr(), delayMs);
+        m_lastQueuedIdleHandlerTask = tmp;
+    }
+}
+
 void WorkerThread::idleHandler()
 {
     ASSERT(m_workerGlobalScope.get());
     int64_t delay = kLongIdleHandlerDelayMs;
+    m_lastQueuedIdleHandlerTask = nullptr;
+
+    // Some tasks may have been started in the mean time, so lets return back
+    // and wait for the next idleHandler to be fired.
+    if (m_tasksCount)
+        return;
 
     // Do a script engine idle notification if the next event is distant enough.
     const double kMinIdleTimespan = 0.3;
+    // This is set to true when idleNotification returns false.
+    // idleNotification returns false only when more GC is required. It returns
+    // true if no more GC is required and that is when callGCAgain will be set to false.
+    bool callGCAgain = false;
     if (m_sharedTimer->nextFireTime() == 0.0 || m_sharedTimer->nextFireTime() > currentTime() + kMinIdleTimespan) {
-        bool hasMoreWork = !m_workerGlobalScope->idleNotification();
-        if (hasMoreWork)
+        callGCAgain = !m_workerGlobalScope->idleNotification();
+        if (callGCAgain)
             delay = kShortIdleHandlerDelayMs;
     }
 
-    postDelayedTask(createSameThreadTask(&WorkerThread::idleHandler, this), delay);
+    if (callGCAgain)
+        queueUpIdleHandlerNow(delay);
+}
+
+int WorkerThread::decrementAndReturnTaskCount()
+{
+    atomicDecrement(&m_tasksCount);
+    return m_tasksCount;
+}
+
+bool WorkerThread::clearIdleHandlerTaskIfSet()
+{
+    // If the event was created more than 3 seconds ago, so its too close to the task completion
+    // hence cancel it and create a new one.
+    const double kIdleHandlerAgeThreshold = 3.0;
+    if (!m_lastQueuedIdleHandlerTask)
+        return true;
+    double idleTaskHandlerAge = currentTime() - m_lastQueuedIdleHandlerTask->creationTimeStamp();
+    if (idleTaskHandlerAge < kIdleHandlerAgeThreshold)
+        return false;
+
+    m_lastQueuedIdleHandlerTask->cancelTask();
+    m_lastQueuedIdleHandlerTask = nullptr;
+
+    return true;
 }
 
 void WorkerThread::postTask(PassOwnPtr<ExecutionContextTask> task)
 {
+    atomicIncrement(&m_tasksCount);
+    clearIdleHandlerTaskIfSet();
     m_thread->postTask(WorkerThreadTask::create(*this, task, true).leakPtr());
 }
 
 void WorkerThread::postDelayedTask(PassOwnPtr<ExecutionContextTask> task, long long delayMs)
 {
+    atomicIncrement(&m_tasksCount);
+    clearIdleHandlerTaskIfSet();
     m_thread->postDelayedTask(WorkerThreadTask::create(*this, task, true).leakPtr(), delayMs);
 }