57 lines
2.2 KiB
C++
57 lines
2.2 KiB
C++
/*
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* Copyright (c) 2016 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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#include "rtc_base/race_checker.h"
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namespace rtc {
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RaceChecker::RaceChecker() {}
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// Note that the implementation here is in itself racy, but we pretend it does
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// not matter because we want this useful in release builds without having to
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// pay the cost of using atomics. A race hitting the race checker is likely to
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// cause access_count_ to diverge from zero and therefore cause the ThreadRef
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// comparison to fail, signaling a race, although it may not be in the exact
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// spot where a race *first* appeared in the code we're trying to protect. There
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// is also a chance that an actual race is missed, however the probability of
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// that has been considered small enough to be an acceptable trade off.
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bool RaceChecker::Acquire() const {
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const PlatformThreadRef current_thread = CurrentThreadRef();
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// Set new accessing thread if this is a new use.
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const int current_access_count = access_count_;
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access_count_ = access_count_ + 1;
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if (current_access_count == 0)
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accessing_thread_ = current_thread;
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// If this is being used concurrently this check will fail for the second
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// thread entering since it won't set the thread. Recursive use of checked
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// methods are OK since the accessing thread remains the same.
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const PlatformThreadRef accessing_thread = accessing_thread_;
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return IsThreadRefEqual(accessing_thread, current_thread);
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}
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void RaceChecker::Release() const {
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access_count_ = access_count_ - 1;
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}
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namespace internal {
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RaceCheckerScope::RaceCheckerScope(const RaceChecker* race_checker)
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: race_checker_(race_checker), race_check_ok_(race_checker->Acquire()) {}
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bool RaceCheckerScope::RaceDetected() const {
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return !race_check_ok_;
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}
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RaceCheckerScope::~RaceCheckerScope() {
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race_checker_->Release();
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}
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} // namespace internal
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} // namespace rtc
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