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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
/* 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 DOM_MEDIA_WEBRTC_LIBWEBRTCGLUE_TASKQUEUEWRAPPER_H_
#define DOM_MEDIA_WEBRTC_LIBWEBRTCGLUE_TASKQUEUEWRAPPER_H_
#include "api/task_queue/task_queue_factory.h"
#include "mozilla/DataMutex.h"
#include "mozilla/RecursiveMutex.h"
#include "mozilla/ProfilerRunnable.h"
#include "mozilla/TaskQueue.h"
#include "VideoUtils.h"
#include "mozilla/media/MediaUtils.h" // For media::Await
namespace mozilla {
enum class DeletionPolicy : uint8_t { Blocking, NonBlocking };
/**
* A wrapper around Mozilla TaskQueues in the shape of a libwebrtc TaskQueue.
*
* Allows libwebrtc to use Mozilla threads where tooling, e.g. profiling, is set
* up and just works.
*
* Mozilla APIs like Runnables, MozPromise, etc. can also be used with the
* wrapped TaskQueue to run things on the right thread when interacting with
* libwebrtc.
*/
template <DeletionPolicy Deletion>
class TaskQueueWrapper : public webrtc::TaskQueueBase {
public:
TaskQueueWrapper(RefPtr<TaskQueue> aTaskQueue, nsCString aName)
: mTaskQueue(std::move(aTaskQueue)), mName(std::move(aName)) {}
~TaskQueueWrapper() = default;
void Delete() override {
{
// Scope this to make sure it does not race against the promise chain we
// set up below.
auto hasShutdown = mHasShutdown.Lock();
*hasShutdown = true;
}
MOZ_RELEASE_ASSERT(Deletion == DeletionPolicy::NonBlocking ||
!mTaskQueue->IsOnCurrentThread());
nsCOMPtr<nsISerialEventTarget> backgroundTaskQueue;
NS_CreateBackgroundTaskQueue(__func__, getter_AddRefs(backgroundTaskQueue));
if (NS_WARN_IF(!backgroundTaskQueue)) {
// Ok... that's pretty broken. Try main instead.
MOZ_ASSERT(false);
backgroundTaskQueue = GetMainThreadSerialEventTarget();
}
RefPtr<GenericPromise> shutdownPromise = mTaskQueue->BeginShutdown()->Then(
backgroundTaskQueue, __func__, [this] {
// Wait until shutdown is complete, then delete for real. Although we
// prevent queued tasks from executing with mHasShutdown, that is a
// member variable, which means we still need to ensure that the
// queue is done executing tasks before destroying it.
delete this;
return GenericPromise::CreateAndResolve(true, __func__);
});
if constexpr (Deletion == DeletionPolicy::Blocking) {
media::Await(backgroundTaskQueue.forget(), shutdownPromise);
} else {
Unused << shutdownPromise;
}
}
already_AddRefed<Runnable> CreateTaskRunner(
absl::AnyInvocable<void() &&> aTask) {
return NS_NewRunnableFunction(
"TaskQueueWrapper::CreateTaskRunner",
[this, task = std::move(aTask),
name = nsPrintfCString("TQ %s: webrtc::QueuedTask",
mName.get())]() mutable {
CurrentTaskQueueSetter current(this);
auto hasShutdown = mHasShutdown.Lock();
if (*hasShutdown) {
return;
}
AUTO_PROFILE_FOLLOWING_RUNNABLE(name);
std::move(task)();
});
}
already_AddRefed<Runnable> CreateTaskRunner(nsCOMPtr<nsIRunnable> aRunnable) {
return NS_NewRunnableFunction(
"TaskQueueWrapper::CreateTaskRunner",
[this, runnable = std::move(aRunnable)]() mutable {
CurrentTaskQueueSetter current(this);
auto hasShutdown = mHasShutdown.Lock();
if (*hasShutdown) {
return;
}
AUTO_PROFILE_FOLLOWING_RUNNABLE(runnable);
runnable->Run();
});
}
void PostTask(absl::AnyInvocable<void() &&> aTask) override {
MOZ_ALWAYS_SUCCEEDS(
mTaskQueue->Dispatch(CreateTaskRunner(std::move(aTask))));
}
void PostDelayedTask(absl::AnyInvocable<void() &&> aTask,
webrtc::TimeDelta aDelay) override {
if (aDelay.ms() == 0) {
// AbstractThread::DelayedDispatch doesn't support delay 0
PostTask(std::move(aTask));
return;
}
MOZ_ALWAYS_SUCCEEDS(mTaskQueue->DelayedDispatch(
CreateTaskRunner(std::move(aTask)), aDelay.ms()));
}
void PostDelayedHighPrecisionTask(absl::AnyInvocable<void() &&> aTask,
webrtc::TimeDelta aDelay) override {
PostDelayedTask(std::move(aTask), aDelay);
}
const RefPtr<TaskQueue> mTaskQueue;
const nsCString mName;
// This is a recursive mutex because a TaskRunner holding this mutex while
// running its runnable may end up running other - tail dispatched - runnables
// too, and they'll again try to grab the mutex.
// The mutex must be held while running the runnable since otherwise there'd
// be a race between shutting down the underlying task queue and the runnable
// dispatching to that task queue (and we assert it succeeds in e.g.,
// PostTask()).
DataMutexBase<bool, RecursiveMutex> mHasShutdown{
false, "TaskQueueWrapper::mHasShutdown"};
};
template <DeletionPolicy Deletion>
class DefaultDelete<TaskQueueWrapper<Deletion>>
: public webrtc::TaskQueueDeleter {
public:
void operator()(TaskQueueWrapper<Deletion>* aPtr) const {
webrtc::TaskQueueDeleter::operator()(aPtr);
}
};
class SharedThreadPoolWebRtcTaskQueueFactory : public webrtc::TaskQueueFactory {
public:
SharedThreadPoolWebRtcTaskQueueFactory() {}
template <DeletionPolicy Deletion>
UniquePtr<TaskQueueWrapper<Deletion>> CreateTaskQueueWrapper(
absl::string_view aName, bool aSupportTailDispatch, Priority aPriority,
MediaThreadType aThreadType = MediaThreadType::WEBRTC_WORKER) const {
// XXX Do something with aPriority
nsCString name(aName.data(), aName.size());
auto taskQueue = TaskQueue::Create(GetMediaThreadPool(aThreadType),
name.get(), aSupportTailDispatch);
return MakeUnique<TaskQueueWrapper<Deletion>>(std::move(taskQueue),
std::move(name));
}
std::unique_ptr<webrtc::TaskQueueBase, webrtc::TaskQueueDeleter>
CreateTaskQueue(absl::string_view aName, Priority aPriority) const override {
// libwebrtc will dispatch some tasks sync, i.e., block the origin thread
// until they've run, and that doesn't play nice with tail dispatching since
// there will never be a tail.
// DeletionPolicy::Blocking because this is for libwebrtc use and that's
// what they expect.
constexpr bool supportTailDispatch = false;
return std::unique_ptr<webrtc::TaskQueueBase, webrtc::TaskQueueDeleter>(
CreateTaskQueueWrapper<DeletionPolicy::Blocking>(
std::move(aName), supportTailDispatch, aPriority)
.release(),
webrtc::TaskQueueDeleter());
}
};
} // namespace mozilla
#endif
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