gecko-dev/dom/media/MediaTaskQueue.h

152 lines
4.5 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef MediaTaskQueue_h_
#define MediaTaskQueue_h_
#include <queue>
#include "mozilla/RefPtr.h"
#include "mozilla/Monitor.h"
#include "SharedThreadPool.h"
#include "nsThreadUtils.h"
#include "MediaPromise.h"
class nsIRunnable;
namespace mozilla {
class SharedThreadPool;
typedef MediaPromise<bool, bool, false> ShutdownPromise;
// Abstracts executing runnables in order in a thread pool. The runnables
// dispatched to the MediaTaskQueue will be executed in the order in which
// they're received, and are guaranteed to not be executed concurrently.
// They may be executed on different threads, and a memory barrier is used
// to make this threadsafe for objects that aren't already threadsafe.
class MediaTaskQueue MOZ_FINAL {
~MediaTaskQueue();
public:
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MediaTaskQueue)
explicit MediaTaskQueue(TemporaryRef<SharedThreadPool> aPool);
nsresult Dispatch(TemporaryRef<nsIRunnable> aRunnable);
// This should only be used for things that absolutely can't afford to be
// flushed. Normal operations should use Dispatch.
nsresult ForceDispatch(TemporaryRef<nsIRunnable> aRunnable);
nsresult SyncDispatch(TemporaryRef<nsIRunnable> aRunnable);
nsresult FlushAndDispatch(TemporaryRef<nsIRunnable> aRunnable);
// Removes all pending tasks from the task queue, and blocks until
// the currently running task (if any) finishes.
void Flush();
// Puts the queue in a shutdown state and returns immediately. The queue will
// remain alive at least until all the events are drained, because the Runners
// hold a strong reference to the task queue, and one of them is always held
// by the threadpool event queue when the task queue is non-empty.
//
// The returned promise is resolved when the queue goes empty.
nsRefPtr<ShutdownPromise> BeginShutdown();
// Blocks until all task finish executing.
void AwaitIdle();
// Blocks until the queue is flagged for shutdown and all tasks have finished
// executing.
void AwaitShutdownAndIdle();
bool IsEmpty();
// Returns true if the current thread is currently running a Runnable in
// the task queue. This is for debugging/validation purposes only.
bool IsCurrentThreadIn();
private:
// Blocks until all task finish executing. Called internally by methods
// that need to wait until the task queue is idle.
// mQueueMonitor must be held.
void AwaitIdleLocked();
enum DispatchMode { AbortIfFlushing, IgnoreFlushing, Forced };
nsresult DispatchLocked(TemporaryRef<nsIRunnable> aRunnable,
DispatchMode aMode);
void FlushLocked();
RefPtr<SharedThreadPool> mPool;
// Monitor that protects the queue and mIsRunning;
Monitor mQueueMonitor;
struct TaskQueueEntry {
RefPtr<nsIRunnable> mRunnable;
bool mForceDispatch;
explicit TaskQueueEntry(TemporaryRef<nsIRunnable> aRunnable,
bool aForceDispatch = false)
: mRunnable(aRunnable), mForceDispatch(aForceDispatch) {}
};
// Queue of tasks to run.
std::queue<TaskQueueEntry> mTasks;
// The thread currently running the task queue. We store a reference
// to this so that IsCurrentThreadIn() can tell if the current thread
// is the thread currently running in the task queue.
RefPtr<nsIThread> mRunningThread;
// True if we've dispatched an event to the pool to execute events from
// the queue.
bool mIsRunning;
// True if we've started our shutdown process.
bool mIsShutdown;
MediaPromiseHolder<ShutdownPromise> mShutdownPromise;
class MOZ_STACK_CLASS AutoSetFlushing
{
public:
explicit AutoSetFlushing(MediaTaskQueue* aTaskQueue) : mTaskQueue(aTaskQueue)
{
mTaskQueue->mQueueMonitor.AssertCurrentThreadOwns();
mTaskQueue->mIsFlushing = true;
}
~AutoSetFlushing()
{
mTaskQueue->mQueueMonitor.AssertCurrentThreadOwns();
mTaskQueue->mIsFlushing = false;
}
private:
MediaTaskQueue* mTaskQueue;
};
// True if we're flushing; we reject new tasks if we're flushing.
bool mIsFlushing;
class Runner : public nsRunnable {
public:
explicit Runner(MediaTaskQueue* aQueue)
: mQueue(aQueue)
{
}
NS_METHOD Run() MOZ_OVERRIDE;
private:
RefPtr<MediaTaskQueue> mQueue;
};
};
} // namespace mozilla
#endif // MediaTaskQueue_h_