[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 2d4f884a4dd7faf10819784ab2d08c195fa878ab..668e8d1d3968cb7df1ec2e977b4f0b020ea2ce9a 100644
--- a/Source/core/workers/WorkerThread.cpp
+++ b/Source/core/workers/WorkerThread.cpp
@@ -164,6 +164,12 @@ public:
             m_task->performTask(workerGlobalScope);
         if (m_isInstrumented)
             InspectorInstrumentation::didPerformExecutionContextTask(workerGlobalScope);
+
+        // If no more tasks are queued up after this, then queue up the idleHandler
+        // to trigger GC.
+        WorkerThread& workerThread = const_cast<WorkerThread&>(m_workerThread);
+        if (!workerThread.decrementAndReturnTaskCount() && !workerThread.isIdleHandlerTaskFiredOnce())

[jochen (gone - plz use gerrit), 2014/09/02 10:14:14]

maybe teach WorkerThreadTask that it's an idle task instead of always
decrementing the task count? then you can't get negative in
decrementAndReturnTaskCount()

[Mayur Kankanwadi, 2014/09/03 11:26:21]

Done.

+            workerThread.queueUpIdleHandlerNow();
     }
 
 private:
@@ -207,6 +213,9 @@ WorkerThread::WorkerThread(WorkerLoaderProxy& workerLoaderProxy, WorkerReporting
     , m_workerReportingProxy(workerReportingProxy)
     , m_startupData(startupData)
     , m_shutdownEvent(adoptPtr(blink::Platform::current()->createWaitableEvent()))
+    , m_tasksCount(0)
+    , m_isIdleHandlerTaskFiredOnce(false)
+    , m_isIdleHandlerTask(false)
 {
     MutexLocker lock(threadSetMutex());
     workerThreads().add(this);
@@ -402,6 +411,19 @@ bool WorkerThread::isCurrentThread() const
     return m_thread && m_thread->isCurrentThread();
 }
 
+bool WorkerThread::isIdleHandlerTaskFiredOnce()
+{
+    MutexLocker lock(m_taskCounterMutex);
+    return m_isIdleHandlerTaskFiredOnce;
+}
+
+void WorkerThread::queueUpIdleHandlerNow()
+{
+    m_isIdleHandlerTask = m_isIdleHandlerTaskFiredOnce = true;
+    postTask(createSameThreadTask(&WorkerThread::idleHandler, this));
+    m_isIdleHandlerTask = false;

[jochen (gone - plz use gerrit), 2014/09/02 10:14:14]

instead of using m_isIdleHandlerTask, this method should just directly create
and post the task on m_thread.

[Mayur Kankanwadi, 2014/09/03 11:26:21]

Done.

+}
+
 void WorkerThread::idleHandler()
 {
     ASSERT(m_workerGlobalScope.get());
@@ -409,22 +431,60 @@ void WorkerThread::idleHandler()
 
     // 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)
+        bool callGCAgain = !m_workerGlobalScope->idleNotification();

[Mayur Kankanwadi, 2014/09/03 11:26:21]

This(bool callGCAgain) was an extra definition, with a good scope for subtle
bugs.
Removed this as well.

+        if (callGCAgain)
             delay = kShortIdleHandlerDelayMs;
     }
+    if (callGCAgain) {
+        postDelayedTask(createSameThreadTask(&WorkerThread::idleHandler, this), delay);
+    }
+}
 
-    postDelayedTask(createSameThreadTask(&WorkerThread::idleHandler, this), delay);
+void WorkerThread::decrementTaskCount()

[jochen (gone - plz use gerrit), 2014/09/02 10:14:14]

this method isn't used anywhere?

[Mayur Kankanwadi, 2014/09/03 11:26:22]

True.Removed it.

+{
+    MutexLocker lock(m_taskCounterMutex);
+    if (!m_tasksCount)
+        return;
+    --m_tasksCount;
+}
+
+unsigned WorkerThread::decrementAndReturnTaskCount()
+{
+    MutexLocker lock(m_taskCounterMutex);
+    if (!m_tasksCount)

[jochen (gone - plz use gerrit), 2014/09/02 10:14:14]

see my comment about not invoking this for idle tasks

[Mayur Kankanwadi, 2014/09/03 11:26:21]

Done.

+        return 0;
+    --m_tasksCount;
+    return m_tasksCount;
+}
+
+unsigned WorkerThread::taskCount()

[jochen (gone - plz use gerrit), 2014/09/02 10:14:14]

not used anywhere?

[Mayur Kankanwadi, 2014/09/03 11:26:22]

True.Removed it.

+{
+    MutexLocker lock(m_taskCounterMutex);
+    return m_tasksCount;
 }
 
 void WorkerThread::postTask(PassOwnPtr<ExecutionContextTask> task)
 {
+    if (!m_isIdleHandlerTask) {
+        MutexLocker lock(m_taskCounterMutex);
+        ++m_tasksCount;
+        m_isIdleHandlerTaskFiredOnce = false;
+    }
     m_thread->postTask(WorkerThreadTask::create(*this, task, true).leakPtr());
 }
 
 void WorkerThread::postDelayedTask(PassOwnPtr<ExecutionContextTask> task, long long delayMs)
 {
+    if (!m_isIdleHandlerTask) {
+        MutexLocker lock(m_taskCounterMutex);
+        ++m_tasksCount;
+        m_isIdleHandlerTaskFiredOnce = false;
+    }
     m_thread->postDelayedTask(WorkerThreadTask::create(*this, task, true).leakPtr(), delayMs);
 }