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ScopedTaskSafety simplifies usage of PendingTaskSafetyFlag, so this CL also includes ToQueuedTask support for ScopedTaskSafety and test updates. This is following up on feedback in the following CL: https://webrtc-review.googlesource.com/c/src/+/174262 Change-Id: Idd38dfc1914b24a05fdc4ad256b409dcf1795fc0 Bug: none Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/174740 Reviewed-by: Karl Wiberg <kwiberg@webrtc.org> Commit-Queue: Tommi <tommi@webrtc.org> Cr-Commit-Position: refs/heads/master@{#31241}
85 lines
2.8 KiB
C++
85 lines
2.8 KiB
C++
/*
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* Copyright 2020 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef RTC_BASE_TASK_UTILS_PENDING_TASK_SAFETY_FLAG_H_
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#define RTC_BASE_TASK_UTILS_PENDING_TASK_SAFETY_FLAG_H_
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#include "api/scoped_refptr.h"
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#include "rtc_base/checks.h"
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#include "rtc_base/ref_count.h"
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#include "rtc_base/synchronization/sequence_checker.h"
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namespace webrtc {
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// Use this flag to drop pending tasks that have been posted to the "main"
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// thread/TQ and end up running after the owning instance has been
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// deleted. The owning instance signals deletion by calling SetNotAlive() from
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// its destructor.
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//
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// When posting a task, post a copy (capture by-value in a lambda) of the flag
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// instance and before performing the work, check the |alive()| state. Abort if
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// alive() returns |false|:
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//
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// // Running outside of the main thread.
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// my_task_queue_->PostTask(ToQueuedTask(
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// [safety = pending_task_safety_flag_, this]() {
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// // Now running on the main thread.
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// if (!safety->alive())
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// return;
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// MyMethod();
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// }));
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//
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// Or implicitly by letting ToQueuedTask do the checking:
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//
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// // Running outside of the main thread.
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// my_task_queue_->PostTask(ToQueuedTask(pending_task_safety_flag_,
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// [this]() { MyMethod(); }));
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//
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// Note that checking the state only works on the construction/destruction
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// thread of the ReceiveStatisticsProxy instance.
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class PendingTaskSafetyFlag : public rtc::RefCountInterface {
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public:
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static rtc::scoped_refptr<PendingTaskSafetyFlag> Create();
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~PendingTaskSafetyFlag() = default;
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void SetNotAlive();
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bool alive() const;
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protected:
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PendingTaskSafetyFlag() = default;
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private:
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bool alive_ = true;
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SequenceChecker main_sequence_;
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};
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// Makes using PendingTaskSafetyFlag very simple. Automatic PTSF creation
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// and signalling of destruction when the ScopedTaskSafety instance goes out
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// of scope.
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// Should be used by the class that wants tasks dropped after destruction.
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// Requirements are that the instance be constructed and destructed on
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// the same thread as the potentially dropped tasks would be running on.
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class ScopedTaskSafety {
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public:
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ScopedTaskSafety() = default;
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~ScopedTaskSafety() { flag_->SetNotAlive(); }
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// Returns a new reference to the safety flag.
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rtc::scoped_refptr<PendingTaskSafetyFlag> flag() const { return flag_; }
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private:
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rtc::scoped_refptr<PendingTaskSafetyFlag> flag_ =
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PendingTaskSafetyFlag::Create();
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};
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} // namespace webrtc
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#endif // RTC_BASE_TASK_UTILS_PENDING_TASK_SAFETY_FLAG_H_
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