blob: 182db2cbbcb1b9c36be127cfaa51c860ec4be94a [file] [log] [blame]
* Copyright 2020 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 "api/scoped_refptr.h"
#include "rtc_base/checks.h"
#include "rtc_base/ref_count.h"
#include "rtc_base/synchronization/sequence_checker.h"
#include "rtc_base/system/no_unique_address.h"
namespace webrtc {
// Use this flag to drop pending tasks that have been posted to the "main"
// thread/TQ and end up running after the owning instance has been
// deleted. The owning instance signals deletion by calling SetNotAlive() from
// its destructor.
// When posting a task, post a copy (capture by-value in a lambda) of the flag
// instance and before performing the work, check the |alive()| state. Abort if
// alive() returns |false|:
// // Running outside of the main thread.
// my_task_queue_->PostTask(ToQueuedTask(
// [safety = pending_task_safety_flag_, this]() {
// // Now running on the main thread.
// if (!safety->alive())
// return;
// MyMethod();
// }));
// Or implicitly by letting ToQueuedTask do the checking:
// // Running outside of the main thread.
// my_task_queue_->PostTask(ToQueuedTask(pending_task_safety_flag_,
// [this]() { MyMethod(); }));
// Note that checking the state only works on the construction/destruction
// thread of the ReceiveStatisticsProxy instance.
class PendingTaskSafetyFlag : public rtc::RefCountInterface {
static rtc::scoped_refptr<PendingTaskSafetyFlag> Create();
~PendingTaskSafetyFlag() = default;
void SetNotAlive();
bool alive() const;
PendingTaskSafetyFlag() = default;
bool alive_ = true;
RTC_NO_UNIQUE_ADDRESS SequenceChecker main_sequence_;
// Makes using PendingTaskSafetyFlag very simple. Automatic PTSF creation
// and signalling of destruction when the ScopedTaskSafety instance goes out
// of scope.
// Should be used by the class that wants tasks dropped after destruction.
// Requirements are that the instance be constructed and destructed on
// the same thread as the potentially dropped tasks would be running on.
class ScopedTaskSafety {
ScopedTaskSafety() = default;
~ScopedTaskSafety() { flag_->SetNotAlive(); }
// Returns a new reference to the safety flag.
rtc::scoped_refptr<PendingTaskSafetyFlag> flag() const { return flag_; }
rtc::scoped_refptr<PendingTaskSafetyFlag> flag_ =
} // namespace webrtc