michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set ts=8 sts=2 et sw=2 tw=80: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "MediaTaskQueue.h"
michael@0: #include "nsThreadUtils.h"
michael@0: #include "SharedThreadPool.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: MediaTaskQueue::MediaTaskQueue(TemporaryRef<SharedThreadPool> aPool)
michael@0:   : mPool(aPool)
michael@0:   , mQueueMonitor("MediaTaskQueue::Queue")
michael@0:   , mIsRunning(false)
michael@0:   , mIsShutdown(false)
michael@0: {
michael@0:   MOZ_COUNT_CTOR(MediaTaskQueue);
michael@0: }
michael@0: 
michael@0: MediaTaskQueue::~MediaTaskQueue()
michael@0: {
michael@0:   MonitorAutoLock mon(mQueueMonitor);
michael@0:   MOZ_ASSERT(mIsShutdown);
michael@0:   MOZ_COUNT_DTOR(MediaTaskQueue);
michael@0: }
michael@0: 
michael@0: nsresult
michael@0: MediaTaskQueue::Dispatch(TemporaryRef<nsIRunnable> aRunnable)
michael@0: {
michael@0:   MonitorAutoLock mon(mQueueMonitor);
michael@0:   if (mIsShutdown) {
michael@0:     return NS_ERROR_FAILURE;
michael@0:   }
michael@0:   mTasks.push(aRunnable);
michael@0:   if (mIsRunning) {
michael@0:     return NS_OK;
michael@0:   }
michael@0:   RefPtr<nsIRunnable> runner(new Runner(this));
michael@0:   nsresult rv = mPool->Dispatch(runner, NS_DISPATCH_NORMAL);
michael@0:   if (NS_FAILED(rv)) {
michael@0:     NS_WARNING("Failed to dispatch runnable to run MediaTaskQueue");
michael@0:     return rv;
michael@0:   }
michael@0:   mIsRunning = true;
michael@0: 
michael@0:   return NS_OK;
michael@0: }
michael@0: 
michael@0: void
michael@0: MediaTaskQueue::AwaitIdle()
michael@0: {
michael@0:   MonitorAutoLock mon(mQueueMonitor);
michael@0:   AwaitIdleLocked();
michael@0: }
michael@0: 
michael@0: void
michael@0: MediaTaskQueue::AwaitIdleLocked()
michael@0: {
michael@0:   mQueueMonitor.AssertCurrentThreadOwns();
michael@0:   MOZ_ASSERT(mIsRunning || mTasks.empty());
michael@0:   while (mIsRunning) {
michael@0:     mQueueMonitor.Wait();
michael@0:   }
michael@0: }
michael@0: 
michael@0: void
michael@0: MediaTaskQueue::Shutdown()
michael@0: {
michael@0:   MonitorAutoLock mon(mQueueMonitor);
michael@0:   mIsShutdown = true;
michael@0:   AwaitIdleLocked();
michael@0: }
michael@0: 
michael@0: void
michael@0: MediaTaskQueue::Flush()
michael@0: {
michael@0:   MonitorAutoLock mon(mQueueMonitor);
michael@0:   while (!mTasks.empty()) {
michael@0:     mTasks.pop();
michael@0:   }
michael@0:   AwaitIdleLocked();
michael@0: }
michael@0: 
michael@0: bool
michael@0: MediaTaskQueue::IsEmpty()
michael@0: {
michael@0:   MonitorAutoLock mon(mQueueMonitor);
michael@0:   return mTasks.empty();
michael@0: }
michael@0: 
michael@0: bool
michael@0: MediaTaskQueue::IsCurrentThreadIn()
michael@0: {
michael@0: #ifdef DEBUG
michael@0:   MonitorAutoLock mon(mQueueMonitor);
michael@0:   return NS_GetCurrentThread() == mRunningThread;
michael@0: #else
michael@0:   return false;
michael@0: #endif
michael@0: }
michael@0: 
michael@0: nsresult
michael@0: MediaTaskQueue::Runner::Run()
michael@0: {
michael@0:   RefPtr<nsIRunnable> event;
michael@0:   {
michael@0:     MonitorAutoLock mon(mQueue->mQueueMonitor);
michael@0:     MOZ_ASSERT(mQueue->mIsRunning);
michael@0:     mQueue->mRunningThread = NS_GetCurrentThread();
michael@0:     if (mQueue->mTasks.size() == 0) {
michael@0:       mQueue->mIsRunning = false;
michael@0:       mon.NotifyAll();
michael@0:       return NS_OK;
michael@0:     }
michael@0:     event = mQueue->mTasks.front();
michael@0:     mQueue->mTasks.pop();
michael@0:   }
michael@0:   MOZ_ASSERT(event);
michael@0: 
michael@0:   // Note that dropping the queue monitor before running the task, and
michael@0:   // taking the monitor again after the task has run ensures we have memory
michael@0:   // fences enforced. This means that if the object we're calling wasn't
michael@0:   // designed to be threadsafe, it will be, provided we're only calling it
michael@0:   // in this task queue.
michael@0:   event->Run();
michael@0: 
michael@0:   // Drop the reference to event. The event will hold a reference to the
michael@0:   // object it's calling, and we don't want to keep it alive, it may be
michael@0:   // making assumptions what holds references to it. This is especially
michael@0:   // the case if the object is waiting for us to shutdown, so that it
michael@0:   // can shutdown (like in the MediaDecoderStateMachine's SHUTDOWN case).
michael@0:   event = nullptr;
michael@0: 
michael@0:   {
michael@0:     MonitorAutoLock mon(mQueue->mQueueMonitor);
michael@0:     if (mQueue->mTasks.size() == 0) {
michael@0:       // No more events to run. Exit the task runner.
michael@0:       mQueue->mIsRunning = false;
michael@0:       mon.NotifyAll();
michael@0:       mQueue->mRunningThread = nullptr;
michael@0:       return NS_OK;
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   // There's at least one more event that we can run. Dispatch this Runner
michael@0:   // to the thread pool again to ensure it runs again. Note that we don't just
michael@0:   // run in a loop here so that we don't hog the thread pool. This means we may
michael@0:   // run on another thread next time, but we rely on the memory fences from
michael@0:   // mQueueMonitor for thread safety of non-threadsafe tasks.
michael@0:   {
michael@0:     MonitorAutoLock mon(mQueue->mQueueMonitor);
michael@0:     // Note: Hold the monitor *before* we dispatch, in case we context switch
michael@0:     // to another thread pool in the queue immediately and take the lock in the
michael@0:     // other thread; mRunningThread could be set to the new thread's value and
michael@0:     // then incorrectly anulled below in that case.
michael@0:     nsresult rv = mQueue->mPool->Dispatch(this, NS_DISPATCH_NORMAL);
michael@0:     if (NS_FAILED(rv)) {
michael@0:       // Failed to dispatch, shutdown!
michael@0:       mQueue->mIsRunning = false;
michael@0:       mQueue->mIsShutdown = true;
michael@0:       mon.NotifyAll();
michael@0:     }
michael@0:     mQueue->mRunningThread = nullptr;
michael@0:   }
michael@0: 
michael@0:   return NS_OK;
michael@0: }
michael@0: 
michael@0: } // namespace mozilla