mirror of
https://github.com/classilla/tenfourfox.git
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210 lines
5.7 KiB
C++
210 lines
5.7 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "mozilla/TaskQueue.h"
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#include "nsThreadUtils.h"
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#include "mozilla/SharedThreadPool.h"
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namespace mozilla {
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TaskQueue::TaskQueue(already_AddRefed<SharedThreadPool> aPool,
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bool aRequireTailDispatch)
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: AbstractThread(aRequireTailDispatch)
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, mPool(aPool)
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, mQueueMonitor("TaskQueue::Queue")
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, mTailDispatcher(nullptr)
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, mIsRunning(false)
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, mIsShutdown(false)
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, mIsFlushing(false)
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{
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MOZ_COUNT_CTOR(TaskQueue);
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}
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TaskQueue::~TaskQueue()
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{
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MonitorAutoLock mon(mQueueMonitor);
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MOZ_ASSERT(mIsShutdown);
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MOZ_COUNT_DTOR(TaskQueue);
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}
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TaskDispatcher&
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TaskQueue::TailDispatcher()
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{
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MOZ_ASSERT(IsCurrentThreadIn());
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MOZ_ASSERT(mTailDispatcher);
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return *mTailDispatcher;
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}
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nsresult
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TaskQueue::DispatchLocked(already_AddRefed<nsIRunnable> aRunnable,
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DispatchMode aMode, DispatchFailureHandling aFailureHandling,
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DispatchReason aReason)
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{
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nsCOMPtr<nsIRunnable> r = aRunnable;
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AbstractThread* currentThread;
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if (aReason != TailDispatch && (currentThread = GetCurrent()) && RequiresTailDispatch(currentThread)) {
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currentThread->TailDispatcher().AddTask(this, r.forget(), aFailureHandling);
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return NS_OK;
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}
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mQueueMonitor.AssertCurrentThreadOwns();
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if (mIsFlushing && aMode == AbortIfFlushing) {
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return NS_ERROR_ABORT;
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}
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if (mIsShutdown) {
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return NS_ERROR_FAILURE;
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}
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mTasks.push(r.forget());
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if (mIsRunning) {
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return NS_OK;
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}
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RefPtr<nsIRunnable> runner(new Runner(this));
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nsresult rv = mPool->Dispatch(runner.forget(), NS_DISPATCH_NORMAL);
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if (NS_FAILED(rv)) {
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NS_WARNING("Failed to dispatch runnable to run TaskQueue");
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return rv;
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}
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mIsRunning = true;
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return NS_OK;
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}
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void
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TaskQueue::AwaitIdle()
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{
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MonitorAutoLock mon(mQueueMonitor);
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AwaitIdleLocked();
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}
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void
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TaskQueue::AwaitIdleLocked()
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{
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// Make sure there are no tasks for this queue waiting in the caller's tail
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// dispatcher.
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MOZ_ASSERT_IF(AbstractThread::GetCurrent(),
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!AbstractThread::GetCurrent()->TailDispatcher().HasTasksFor(this));
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mQueueMonitor.AssertCurrentThreadOwns();
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MOZ_ASSERT(mIsRunning || mTasks.empty());
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while (mIsRunning) {
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mQueueMonitor.Wait();
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}
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}
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void
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TaskQueue::AwaitShutdownAndIdle()
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{
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// Make sure there are no tasks for this queue waiting in the caller's tail
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// dispatcher.
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MOZ_ASSERT_IF(AbstractThread::GetCurrent(),
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!AbstractThread::GetCurrent()->TailDispatcher().HasTasksFor(this));
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MonitorAutoLock mon(mQueueMonitor);
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while (!mIsShutdown) {
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mQueueMonitor.Wait();
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}
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AwaitIdleLocked();
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}
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RefPtr<ShutdownPromise>
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TaskQueue::BeginShutdown()
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{
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// Dispatch any tasks for this queue waiting in the caller's tail dispatcher,
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// since this is the last opportunity to do so.
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if (AbstractThread* currentThread = AbstractThread::GetCurrent()) {
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currentThread->TailDispatcher().DispatchTasksFor(this);
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}
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MonitorAutoLock mon(mQueueMonitor);
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mIsShutdown = true;
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RefPtr<ShutdownPromise> p = mShutdownPromise.Ensure(__func__);
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MaybeResolveShutdown();
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mon.NotifyAll();
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return p;
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}
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bool
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TaskQueue::IsEmpty()
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{
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MonitorAutoLock mon(mQueueMonitor);
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return mTasks.empty();
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}
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bool
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TaskQueue::IsCurrentThreadIn()
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{
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bool in = NS_GetCurrentThread() == mRunningThread;
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MOZ_ASSERT(in == (GetCurrent() == this));
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return in;
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}
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nsresult
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TaskQueue::Runner::Run()
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{
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RefPtr<nsIRunnable> event;
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{
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MonitorAutoLock mon(mQueue->mQueueMonitor);
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MOZ_ASSERT(mQueue->mIsRunning);
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if (mQueue->mTasks.size() == 0) {
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mQueue->mIsRunning = false;
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mQueue->MaybeResolveShutdown();
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mon.NotifyAll();
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return NS_OK;
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}
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event = mQueue->mTasks.front().forget();
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mQueue->mTasks.pop();
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}
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MOZ_ASSERT(event);
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// Note that dropping the queue monitor before running the task, and
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// taking the monitor again after the task has run ensures we have memory
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// fences enforced. This means that if the object we're calling wasn't
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// designed to be threadsafe, it will be, provided we're only calling it
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// in this task queue.
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{
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AutoTaskGuard g(mQueue);
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event->Run();
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}
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// Drop the reference to event. The event will hold a reference to the
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// object it's calling, and we don't want to keep it alive, it may be
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// making assumptions what holds references to it. This is especially
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// the case if the object is waiting for us to shutdown, so that it
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// can shutdown (like in the MediaDecoderStateMachine's SHUTDOWN case).
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event = nullptr;
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{
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MonitorAutoLock mon(mQueue->mQueueMonitor);
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if (mQueue->mTasks.size() == 0) {
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// No more events to run. Exit the task runner.
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mQueue->mIsRunning = false;
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mQueue->MaybeResolveShutdown();
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mon.NotifyAll();
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return NS_OK;
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}
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}
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// There's at least one more event that we can run. Dispatch this Runner
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// to the thread pool again to ensure it runs again. Note that we don't just
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// run in a loop here so that we don't hog the thread pool. This means we may
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// run on another thread next time, but we rely on the memory fences from
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// mQueueMonitor for thread safety of non-threadsafe tasks.
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nsresult rv = mQueue->mPool->Dispatch(this, NS_DISPATCH_NORMAL);
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if (NS_FAILED(rv)) {
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// Failed to dispatch, shutdown!
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MonitorAutoLock mon(mQueue->mQueueMonitor);
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mQueue->mIsRunning = false;
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mQueue->mIsShutdown = true;
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mQueue->MaybeResolveShutdown();
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mon.NotifyAll();
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}
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return NS_OK;
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}
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} // namespace mozilla
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