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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 PostTaskImpl(absl::AnyInvocable<void() &&> aTask,
+ const PostTaskTraits& aTraits,
+ const webrtc::Location& aLocation) override {
+ MOZ_ALWAYS_SUCCEEDS(
+ mTaskQueue->Dispatch(CreateTaskRunner(std::move(aTask))));
+ }
+
+ void PostDelayedTaskImpl(absl::AnyInvocable<void() &&> aTask,
+ webrtc::TimeDelta aDelay,
+ const PostDelayedTaskTraits& aTraits,
+ const webrtc::Location& aLocation) override {
+ if (aDelay.ms() == 0) {
+ // AbstractThread::DelayedDispatch doesn't support delay 0
+ PostTaskImpl(std::move(aTask), PostTaskTraits{}, aLocation);
+ return;
+ }
+ MOZ_ALWAYS_SUCCEEDS(mTaskQueue->DelayedDispatch(
+ CreateTaskRunner(std::move(aTask)), aDelay.ms()));
+ }
+
+ 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