mirror of
https://github.com/classilla/tenfourfox.git
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177 lines
5.4 KiB
C++
177 lines
5.4 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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#ifndef TaskQueue_h_
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#define TaskQueue_h_
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#include "mozilla/Monitor.h"
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#include "mozilla/MozPromise.h"
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#include "mozilla/RefPtr.h"
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#include "mozilla/TaskDispatcher.h"
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#include "mozilla/unused.h"
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#include <queue>
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#include "mozilla/SharedThreadPool.h"
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#include "nsThreadUtils.h"
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class nsIRunnable;
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namespace mozilla {
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class SharedThreadPool;
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typedef MozPromise<bool, bool, false> ShutdownPromise;
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// Abstracts executing runnables in order in a thread pool. The runnables
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// dispatched to the TaskQueue will be executed in the order in which
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// they're received, and are guaranteed to not be executed concurrently.
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// They may be executed on different threads, and a memory barrier is used
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// to make this threadsafe for objects that aren't already threadsafe.
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class TaskQueue : public AbstractThread {
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public:
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explicit TaskQueue(already_AddRefed<SharedThreadPool> aPool, bool aSupportsTailDispatch = false);
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TaskDispatcher& TailDispatcher() override;
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TaskQueue* AsTaskQueue() override { return this; }
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void Dispatch(already_AddRefed<nsIRunnable> aRunnable,
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DispatchFailureHandling aFailureHandling = AssertDispatchSuccess,
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DispatchReason aReason = NormalDispatch) override
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{
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MonitorAutoLock mon(mQueueMonitor);
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nsresult rv = DispatchLocked(Move(aRunnable), AbortIfFlushing, aFailureHandling, aReason);
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MOZ_DIAGNOSTIC_ASSERT(aFailureHandling == DontAssertDispatchSuccess || NS_SUCCEEDED(rv));
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Unused << rv;
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}
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// Puts the queue in a shutdown state and returns immediately. The queue will
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// remain alive at least until all the events are drained, because the Runners
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// hold a strong reference to the task queue, and one of them is always held
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// by the threadpool event queue when the task queue is non-empty.
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//
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// The returned promise is resolved when the queue goes empty.
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RefPtr<ShutdownPromise> BeginShutdown();
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// Blocks until all task finish executing.
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void AwaitIdle();
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// Blocks until the queue is flagged for shutdown and all tasks have finished
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// executing.
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void AwaitShutdownAndIdle();
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bool IsEmpty();
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// Returns true if the current thread is currently running a Runnable in
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// the task queue.
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bool IsCurrentThreadIn() override;
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protected:
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virtual ~TaskQueue();
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// Blocks until all task finish executing. Called internally by methods
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// that need to wait until the task queue is idle.
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// mQueueMonitor must be held.
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void AwaitIdleLocked();
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enum DispatchMode { AbortIfFlushing, IgnoreFlushing };
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nsresult DispatchLocked(already_AddRefed<nsIRunnable> aRunnable, DispatchMode aMode,
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DispatchFailureHandling aFailureHandling,
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DispatchReason aReason = NormalDispatch);
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void MaybeResolveShutdown()
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{
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mQueueMonitor.AssertCurrentThreadOwns();
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if (mIsShutdown && !mIsRunning) {
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mShutdownPromise.ResolveIfExists(true, __func__);
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mPool = nullptr;
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}
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}
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RefPtr<SharedThreadPool> mPool;
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// Monitor that protects the queue and mIsRunning;
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Monitor mQueueMonitor;
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// Queue of tasks to run.
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std::queue<nsCOMPtr<nsIRunnable>> mTasks;
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// The thread currently running the task queue. We store a reference
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// to this so that IsCurrentThreadIn() can tell if the current thread
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// is the thread currently running in the task queue.
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//
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// This may be read on any thread, but may only be written on mRunningThread.
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// The thread can't die while we're running in it, and we only use it for
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// pointer-comparison with the current thread anyway - so we make it atomic
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// and don't refcount it.
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Atomic<nsIThread*> mRunningThread;
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// RAII class that gets instantiated for each dispatched task.
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class AutoTaskGuard : public AutoTaskDispatcher
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{
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public:
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explicit AutoTaskGuard(TaskQueue* aQueue)
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: AutoTaskDispatcher(/* aIsTailDispatcher = */ true), mQueue(aQueue)
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{
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// NB: We don't hold the lock to aQueue here. Don't do anything that
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// might require it.
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MOZ_ASSERT(!mQueue->mTailDispatcher);
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mQueue->mTailDispatcher = this;
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MOZ_ASSERT(sCurrentThreadTLS.get() == nullptr);
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sCurrentThreadTLS.set(aQueue);
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MOZ_ASSERT(mQueue->mRunningThread == nullptr);
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mQueue->mRunningThread = NS_GetCurrentThread();
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}
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~AutoTaskGuard()
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{
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DrainDirectTasks();
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MOZ_ASSERT(mQueue->mRunningThread == NS_GetCurrentThread());
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mQueue->mRunningThread = nullptr;
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sCurrentThreadTLS.set(nullptr);
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mQueue->mTailDispatcher = nullptr;
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}
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private:
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TaskQueue* mQueue;
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};
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TaskDispatcher* mTailDispatcher;
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// True if we've dispatched an event to the pool to execute events from
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// the queue.
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bool mIsRunning;
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// True if we've started our shutdown process.
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bool mIsShutdown;
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MozPromiseHolder<ShutdownPromise> mShutdownPromise;
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// True if we're flushing; we reject new tasks if we're flushing.
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bool mIsFlushing;
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class Runner : public nsRunnable {
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public:
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explicit Runner(TaskQueue* aQueue)
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: mQueue(aQueue)
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{
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}
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NS_METHOD Run() override;
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private:
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RefPtr<TaskQueue> mQueue;
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};
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};
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} // namespace mozilla
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#endif // TaskQueue_h_
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