blob: 89e4e778ea833b2a7986e656f340c40fee300966 [file] [log] [blame]
* Copyright 2014 The WebRTC Project Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include "webrtc/rtc_base/asyncinvoker.h"
#include "webrtc/rtc_base/checks.h"
#include "webrtc/rtc_base/logging.h"
namespace rtc {
: pending_invocations_(0),
invocation_complete_(new RefCountedObject<Event>(false, false)),
destroying_(false) {}
AsyncInvoker::~AsyncInvoker() {, std::memory_order_relaxed);
// Messages for this need to be cleared *before* our destructor is complete.
// And we need to wait for any invocations that are still in progress on
// other threads. Using memory_order_acquire for synchronization with
// AsyncClosure destructors.
while (pending_invocations_.load(std::memory_order_acquire) > 0) {
// If the destructor was called while AsyncInvoke was being called by
// another thread, WITHIN an AsyncInvoked functor, it may do another
// Thread::Post even after we called MessageQueueManager::Clear(this). So
// we need to keep calling Clear to discard these posts.
void AsyncInvoker::OnMessage(Message* msg) {
// Get the AsyncClosure shared ptr from this message's data.
ScopedMessageData<AsyncClosure>* data =
// Execute the closure and trigger the return message if needed.
delete data;
void AsyncInvoker::Flush(Thread* thread, uint32_t id /*= MQID_ANY*/) {
// If the destructor is waiting for invocations to finish, don't start
// running even more tasks.
if (destroying_.load(std::memory_order_relaxed))
// Run this on |thread| to reduce the number of context switches.
if (Thread::Current() != thread) {
Bind(&AsyncInvoker::Flush, this, thread, id));
MessageList removed;
thread->Clear(this, id, &removed);
for (MessageList::iterator it = removed.begin(); it != removed.end(); ++it) {
// This message was pending on this thread, so run it now.
thread->Send(it->posted_from, it->phandler, it->message_id, it->pdata);
void AsyncInvoker::DoInvoke(const Location& posted_from,
Thread* thread,
std::unique_ptr<AsyncClosure> closure,
uint32_t id) {
if (destroying_.load(std::memory_order_relaxed)) {
// Note that this may be expected, if the application is AsyncInvoking
// tasks that AsyncInvoke other tasks. But otherwise it indicates a race
// between a thread destroying the AsyncInvoker and a thread still trying
// to use it.
LOG(LS_WARNING) << "Tried to invoke while destroying the invoker.";
thread->Post(posted_from, this, id,
new ScopedMessageData<AsyncClosure>(std::move(closure)));
void AsyncInvoker::DoInvokeDelayed(const Location& posted_from,
Thread* thread,
std::unique_ptr<AsyncClosure> closure,
uint32_t delay_ms,
uint32_t id) {
if (destroying_.load(std::memory_order_relaxed)) {
// See above comment.
LOG(LS_WARNING) << "Tried to invoke while destroying the invoker.";
thread->PostDelayed(posted_from, delay_ms, this, id,
new ScopedMessageData<AsyncClosure>(std::move(closure)));
GuardedAsyncInvoker::GuardedAsyncInvoker() : thread_(Thread::Current()) {
GuardedAsyncInvoker::~GuardedAsyncInvoker() {
bool GuardedAsyncInvoker::Flush(uint32_t id) {
CritScope cs(&crit_);
if (thread_ == nullptr)
return false;
invoker_.Flush(thread_, id);
return true;
void GuardedAsyncInvoker::ThreadDestroyed() {
CritScope cs(&crit_);
// We should never get more than one notification about the thread dying.
RTC_DCHECK(thread_ != nullptr);
thread_ = nullptr;
AsyncClosure::AsyncClosure(AsyncInvoker* invoker)
: invoker_(invoker), invocation_complete_(invoker_->invocation_complete_) {
invoker_->pending_invocations_.fetch_add(1, std::memory_order_relaxed);
AsyncClosure::~AsyncClosure() {
// Using memory_order_release for synchronization with the AsyncInvoker
// destructor.
invoker_->pending_invocations_.fetch_sub(1, std::memory_order_release);
// After |pending_invocations_| is decremented, we may need to signal
// |invocation_complete_| in case the AsyncInvoker is being destroyed and
// waiting for pending tasks to complete.
// It's also possible that the destructor finishes before "Set()" is called,
// which is safe because the event is reference counted (and in a thread-safe
// way).
} // namespace rtc