[Blink-WebWorkers] WorkerSharedTimer cancels extra delayed 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 988256e367b9a256b1245ff2fdac409fb9aa786d..e5fe43132ef59d5e9d4b651d10fbe30a46698b6e 100644
--- a/Source/core/workers/WorkerThread.cpp
+++ b/Source/core/workers/WorkerThread.cpp
@@ -85,6 +85,74 @@ unsigned WorkerThread::workerThreadCount()
     return workerThreads().size();
 }
 
+class WorkerThreadTask : public blink::WebThread::Task {

[jochen (gone - plz use gerrit), 2014/09/15 14:29:41]

why do you move this class up here?

[Mayur Kankanwadi, 2014/09/15 14:38:27]

Was done to fix earlier compilation errors. Fixed to the right place now.
Acknowledged.

+    WTF_MAKE_NONCOPYABLE(WorkerThreadTask); WTF_MAKE_FAST_ALLOCATED;
+public:
+    static PassOwnPtr<WorkerThreadTask> create(const WorkerThread& workerThread, PassOwnPtr<ExecutionContextTask> task, bool isInstrumented)
+    {
+        return adoptPtr(new WorkerThreadTask(workerThread, task, isInstrumented));
+    }
+
+    virtual ~WorkerThreadTask() { }
+
+    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;
+
+        if (m_isInstrumented)
+            InspectorInstrumentation::willPerformExecutionContextTask(workerGlobalScope, m_task.get());
+        if ((!workerGlobalScope->isClosing() && !m_workerThread.terminated()) || m_task->isCleanupTask())
+            m_task->performTask(workerGlobalScope);
+        if (m_isInstrumented)
+            InspectorInstrumentation::didPerformExecutionContextTask(workerGlobalScope);
+    }
+
+private:
+    WorkerThreadTask(const 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());
+    }
+
+    const WorkerThread& m_workerThread;
+    OwnPtr<ExecutionContextTask> m_task;
+    bool m_isInstrumented;
+};
+
+class WorkerThreadCancelableTask FINAL : public ExecutionContextTask {

[jochen (gone - plz use gerrit), 2014/09/15 14:29:42]

add wtf_make_noncopyable and fast allocated macros

[Mayur Kankanwadi, 2014/09/15 14:38:27]

Done.

+public:
+    static PassOwnPtr<WorkerThreadCancelableTask> create(const Closure& closure)
+    {
+        return adoptPtr(new WorkerThreadCancelableTask(closure));
+    }
+
+    virtual void performTask(ExecutionContext*) OVERRIDE
+    {
+        if (!m_taskCanceled)
+            m_closure();
+    }
+
+    void cancelTask() { m_taskCanceled = true; }
+
+private:
+    explicit WorkerThreadCancelableTask(const Closure& closure)
+    : m_closure(closure)
+    , m_taskCanceled(false)
+    { }
+
+    Closure m_closure;
+    bool m_taskCanceled;
+};
+
 class WorkerSharedTimer : public SharedTimer {
 public:
     explicit WorkerSharedTimer(WorkerThread* workerThread)
@@ -116,12 +184,28 @@ public:
 
         m_running = true;
         m_nextFireTime = currentTime() + interval;
-        m_workerThread->postDelayedTask(createSameThreadTask(&WorkerSharedTimer::OnTimeout, this), delay);
+        if (m_lastQueuedTask) {
+            // If something was queued up before this, check if its later than the current timer
+            if (interval < m_lastQueuedTaskTimer->nextFireInterval()) {
+                m_lastQueuedTask->cancelTask();
+                m_lastQueuedTask = 0;
+                m_lastQueuedTaskTimer = 0;
+            }
+        }
+        if (!m_lastQueuedTask) {
+            // Now queue the task as a cancellable one.
+            m_lastQueuedTask = WorkerThreadCancelableTask::create(bind(&WorkerSharedTimer::OnTimeout, this)).leakPtr();
+            m_workerThread->postDelayedTask(adoptPtr(m_lastQueuedTask), delay);
+            // The current timer should ideally be at the top of the heap as its assumed to be the smallest interval in the heap
+            m_lastQueuedTaskTimer = PlatformThreadData::current().threadTimers().timerHeap().first();
+        }
     }
 
     virtual void stop()
     {
         m_running = false;
+        m_lastQueuedTask = 0;
+        m_lastQueuedTaskTimer = 0;
     }
 
     double nextFireTime() { return m_nextFireTime; }
@@ -130,6 +214,10 @@ private:
     void OnTimeout()
     {
         ASSERT(m_workerThread->workerGlobalScope());
+
+        m_lastQueuedTask = 0;
+        m_lastQueuedTaskTimer = 0;
+
         if (m_sharedTimerFunction && m_running && !m_workerThread->workerGlobalScope()->isClosing())
             m_sharedTimerFunction();
     }
@@ -138,50 +226,12 @@ private:
     SharedTimerFunction m_sharedTimerFunction;
     double m_nextFireTime;
     bool m_running;
+    static WorkerThreadCancelableTask* m_lastQueuedTask;

[jochen (gone - plz use gerrit), 2014/09/15 14:29:42]

why static? there can be several worker threads

[Mayur Kankanwadi, 2014/09/15 14:38:27]

Yes, it's unnecessary.
Acknowledged.

+    static TimerBase* m_lastQueuedTaskTimer;
 };
 
-class WorkerThreadTask : public blink::WebThread::Task {
-    WTF_MAKE_NONCOPYABLE(WorkerThreadTask); WTF_MAKE_FAST_ALLOCATED;
-public:
-    static PassOwnPtr<WorkerThreadTask> create(const WorkerThread& workerThread, PassOwnPtr<ExecutionContextTask> task, bool isInstrumented)
-    {
-        return adoptPtr(new WorkerThreadTask(workerThread, task, isInstrumented));
-    }
-
-    virtual ~WorkerThreadTask() { }
-
-    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;
-
-        if (m_isInstrumented)
-            InspectorInstrumentation::willPerformExecutionContextTask(workerGlobalScope, m_task.get());
-        if ((!workerGlobalScope->isClosing() && !m_workerThread.terminated()) || m_task->isCleanupTask())
-            m_task->performTask(workerGlobalScope);
-        if (m_isInstrumented)
-            InspectorInstrumentation::didPerformExecutionContextTask(workerGlobalScope);
-    }
-
-private:
-    WorkerThreadTask(const 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());
-    }
-
-    const WorkerThread& m_workerThread;
-    OwnPtr<ExecutionContextTask> m_task;
-    bool m_isInstrumented;
-};
+WorkerThreadCancelableTask* WorkerSharedTimer::m_lastQueuedTask = 0;
+TimerBase* WorkerSharedTimer::m_lastQueuedTaskTimer = 0;
 
 class RunDebuggerQueueTask FINAL : public ExecutionContextTask {
 public: