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f70fbc8411
This change introduces a new non-reentrant mutex to WebRTC. It enables eventual migration to Abseil's mutex. The mutex types supportable by webrtc::Mutex are - absl::Mutex - CriticalSection (Windows only) - pthread_mutex (POSIX only) In addition to introducing the mutexes, the CL also changes PacketBuffer to use the new mutex instead of rtc::CriticalSection. The method of yielding from critical_section.cc was given a mini-cleanup and YieldCurrentThread() was added to rtc_base/synchronization/yield.h/cc. Additionally, google_benchmark benchmarks for the mutexes were added (test courtesy of danilchap@), and some results from a pthread/Abseil shootout were added showing Abseil has the advantage in higher contention. Bug: webrtc:11567, webrtc:11634 Change-Id: Iaec324ccb32ec3851bf6db3fd290f5ea5dee4c81 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/176230 Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org> Reviewed-by: Tommi <tommi@webrtc.org> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#31443}
103 lines
2.9 KiB
C++
103 lines
2.9 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_SYNCHRONIZATION_MUTEX_H_
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#define RTC_BASE_SYNCHRONIZATION_MUTEX_H_
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#include <atomic>
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#include "absl/base/const_init.h"
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#include "rtc_base/checks.h"
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#include "rtc_base/system/unused.h"
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#include "rtc_base/thread_annotations.h"
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#if defined(WEBRTC_ABSL_MUTEX)
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#include "rtc_base/synchronization/mutex_abseil.h"
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#elif defined(WEBRTC_WIN)
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#include "rtc_base/synchronization/mutex_critical_section.h"
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#elif defined(WEBRTC_POSIX)
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#include "rtc_base/synchronization/mutex_pthread.h"
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#else
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#error Unsupported platform.
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#endif
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namespace webrtc {
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// The Mutex guarantees exclusive access and aims to follow Abseil semantics
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// (i.e. non-reentrant etc).
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class RTC_LOCKABLE Mutex final {
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public:
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Mutex() = default;
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Mutex(const Mutex&) = delete;
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Mutex& operator=(const Mutex&) = delete;
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void Lock() RTC_EXCLUSIVE_LOCK_FUNCTION() { impl_.Lock(); }
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RTC_WARN_UNUSED_RESULT bool TryLock() RTC_EXCLUSIVE_TRYLOCK_FUNCTION(true) {
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return impl_.TryLock();
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}
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void Unlock() RTC_UNLOCK_FUNCTION() { impl_.Unlock(); }
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private:
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MutexImpl impl_;
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};
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// MutexLock, for serializing execution through a scope.
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class RTC_SCOPED_LOCKABLE MutexLock final {
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public:
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MutexLock(const MutexLock&) = delete;
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MutexLock& operator=(const MutexLock&) = delete;
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explicit MutexLock(Mutex* mutex) RTC_EXCLUSIVE_LOCK_FUNCTION(mutex)
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: mutex_(mutex) {
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mutex->Lock();
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}
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~MutexLock() RTC_UNLOCK_FUNCTION() { mutex_->Unlock(); }
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private:
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Mutex* mutex_;
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};
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// A mutex used to protect global variables. Do NOT use for other purposes.
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#if defined(WEBRTC_ABSL_MUTEX)
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using GlobalMutex = absl::Mutex;
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using GlobalMutexLock = absl::MutexLock;
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#else
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class RTC_LOCKABLE GlobalMutex final {
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public:
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GlobalMutex(const GlobalMutex&) = delete;
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GlobalMutex& operator=(const GlobalMutex&) = delete;
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constexpr explicit GlobalMutex(absl::ConstInitType /*unused*/)
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: mutex_locked_(0) {}
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void Lock() RTC_EXCLUSIVE_LOCK_FUNCTION();
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void Unlock() RTC_UNLOCK_FUNCTION();
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private:
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std::atomic<int> mutex_locked_; // 0 means lock not taken, 1 means taken.
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};
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// GlobalMutexLock, for serializing execution through a scope.
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class RTC_SCOPED_LOCKABLE GlobalMutexLock final {
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public:
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GlobalMutexLock(const GlobalMutexLock&) = delete;
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GlobalMutexLock& operator=(const GlobalMutexLock&) = delete;
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explicit GlobalMutexLock(GlobalMutex* mutex) RTC_EXCLUSIVE_LOCK_FUNCTION();
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~GlobalMutexLock() RTC_UNLOCK_FUNCTION();
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private:
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GlobalMutex* mutex_;
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};
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#endif // if defined(WEBRTC_ABSL_MUTEX)
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} // namespace webrtc
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#endif // RTC_BASE_SYNCHRONIZATION_MUTEX_H_
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