Line data    Source code

       1             : /*
       2             :  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
       3             :  *
       4             :  *  Use of this source code is governed by a BSD-style license
       5             :  *  that can be found in the LICENSE file in the root of the source
       6             :  *  tree. An additional intellectual property rights grant can be found
       7             :  *  in the file PATENTS.  All contributing project authors may
       8             :  *  be found in the AUTHORS file in the root of the source tree.
       9             :  */
      10             : 
      11             : #include "webrtc/base/race_checker.h"
      12             : 
      13             : namespace rtc {
      14             : 
      15           0 : RaceChecker::RaceChecker() {}
      16             : 
      17             : // Note that the implementation here is in itself racy, but we pretend it does
      18             : // not matter because we want this useful in release builds without having to
      19             : // pay the cost of using atomics. A race hitting the race checker is likely to
      20             : // cause access_count_ to diverge from zero and therefore cause the ThreadRef
      21             : // comparison to fail, signaling a race, although it may not be in the exact
      22             : // spot where a race *first* appeared in the code we're trying to protect. There
      23             : // is also a chance that an actual race is missed, however the probability of
      24             : // that has been considered small enough to be an acceptable trade off.
      25           0 : bool RaceChecker::Acquire() const {
      26           0 :   const PlatformThreadRef current_thread = CurrentThreadRef();
      27             :   // Set new accessing thread if this is a new use.
      28           0 :   if (access_count_++ == 0)
      29           0 :     accessing_thread_ = current_thread;
      30             :   // If this is being used concurrently this check will fail for the second
      31             :   // thread entering since it won't set the thread. Recursive use of checked
      32             :   // methods are OK since the accessing thread remains the same.
      33           0 :   const PlatformThreadRef accessing_thread = accessing_thread_;
      34           0 :   return IsThreadRefEqual(accessing_thread, current_thread);
      35             : }
      36             : 
      37           0 : void RaceChecker::Release() const {
      38           0 :   --access_count_;
      39           0 : }
      40             : 
      41             : namespace internal {
      42           0 : RaceCheckerScope::RaceCheckerScope(const RaceChecker* race_checker)
      43           0 :     : race_checker_(race_checker), race_check_ok_(race_checker->Acquire()) {}
      44             : 
      45           0 : bool RaceCheckerScope::RaceDetected() const {
      46           0 :   return !race_check_ok_;
      47             : }
      48             : 
      49           0 : RaceCheckerScope::~RaceCheckerScope() {
      50           0 :   race_checker_->Release();
      51           0 : }
      52             : 
      53             : }  // namespace internal
      54             : }  // namespace rtc