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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 #ifndef RTC_BASE_RACE_CHECKER_H_
12 #define RTC_BASE_RACE_CHECKER_H_
13 
14 #include "rtc_base/checks.h"
15 #include "rtc_base/platform_thread_types.h"
16 #include "rtc_base/thread_annotations.h"
17 
18 namespace rtc {
19 
20 namespace internal {
21 class RaceCheckerScope;
22 }  // namespace internal
23 
24 // Best-effort race-checking implementation. This primitive uses no
25 // synchronization at all to be as-fast-as-possible in the non-racy case.
26 class RTC_LOCKABLE RaceChecker {
27  public:
28   friend class internal::RaceCheckerScope;
29   RaceChecker();
30 
31  private:
32   bool Acquire() const RTC_EXCLUSIVE_LOCK_FUNCTION();
33   void Release() const RTC_UNLOCK_FUNCTION();
34 
35   // Volatile to prevent code being optimized away in Acquire()/Release().
36   mutable volatile int access_count_ = 0;
37   mutable volatile PlatformThreadRef accessing_thread_;
38 };
39 
40 namespace internal {
41 class RTC_SCOPED_LOCKABLE RaceCheckerScope {
42  public:
43   explicit RaceCheckerScope(const RaceChecker* race_checker)
44       RTC_EXCLUSIVE_LOCK_FUNCTION(race_checker);
45 
46   bool RaceDetected() const;
47   ~RaceCheckerScope() RTC_UNLOCK_FUNCTION();
48 
49  private:
50   const RaceChecker* const race_checker_;
51   const bool race_check_ok_;
52 };
53 
54 class RTC_SCOPED_LOCKABLE RaceCheckerScopeDoNothing {
55  public:
RaceCheckerScopeDoNothing(const RaceChecker * race_checker)56   explicit RaceCheckerScopeDoNothing(const RaceChecker* race_checker)
57       RTC_EXCLUSIVE_LOCK_FUNCTION(race_checker) {}
58 
RTC_UNLOCK_FUNCTION()59   ~RaceCheckerScopeDoNothing() RTC_UNLOCK_FUNCTION() {}
60 };
61 
62 }  // namespace internal
63 }  // namespace rtc
64 
65 #define RTC_CHECK_RUNS_SERIALIZED(x)               \
66   rtc::internal::RaceCheckerScope race_checker(x); \
67   RTC_CHECK(!race_checker.RaceDetected())
68 
69 #if RTC_DCHECK_IS_ON
70 #define RTC_DCHECK_RUNS_SERIALIZED(x)              \
71   rtc::internal::RaceCheckerScope race_checker(x); \
72   RTC_DCHECK(!race_checker.RaceDetected())
73 #else
74 #define RTC_DCHECK_RUNS_SERIALIZED(x) \
75   rtc::internal::RaceCheckerScopeDoNothing race_checker(x)
76 #endif
77 
78 #endif  // RTC_BASE_RACE_CHECKER_H_
79