1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
/*
* Copyright 2020 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef RTC_BASE_SYNCHRONIZATION_MUTEX_PTHREAD_H_
#define RTC_BASE_SYNCHRONIZATION_MUTEX_PTHREAD_H_
#if defined(WEBRTC_POSIX)
#include <pthread.h>
#if defined(WEBRTC_MAC)
#include <pthread_spis.h>
#endif
#include "absl/base/attributes.h"
#include "rtc_base/system/no_unique_address.h"
#include "rtc_base/thread_annotations.h"
namespace webrtc {
class RTC_LOCKABLE MutexImpl final {
public:
MutexImpl() {
pthread_mutexattr_t mutex_attribute;
pthread_mutexattr_init(&mutex_attribute);
#if defined(WEBRTC_MAC)
pthread_mutexattr_setpolicy_np(&mutex_attribute,
_PTHREAD_MUTEX_POLICY_FIRSTFIT);
#endif
pthread_mutex_init(&mutex_, &mutex_attribute);
pthread_mutexattr_destroy(&mutex_attribute);
}
MutexImpl(const MutexImpl&) = delete;
MutexImpl& operator=(const MutexImpl&) = delete;
~MutexImpl() { pthread_mutex_destroy(&mutex_); }
void Lock() RTC_EXCLUSIVE_LOCK_FUNCTION() {
pthread_mutex_lock(&mutex_);
owner_.SetOwner();
}
ABSL_MUST_USE_RESULT bool TryLock() RTC_EXCLUSIVE_TRYLOCK_FUNCTION(true) {
if (pthread_mutex_trylock(&mutex_) != 0) {
return false;
}
owner_.SetOwner();
return true;
}
void AssertHeld() const RTC_ASSERT_EXCLUSIVE_LOCK() { owner_.AssertOwned(); }
void Unlock() RTC_UNLOCK_FUNCTION() {
owner_.ClearOwner();
pthread_mutex_unlock(&mutex_);
}
private:
class OwnerRecord {
public:
#if !RTC_DCHECK_IS_ON
void SetOwner() {}
void ClearOwner() {}
void AssertOwned() const {}
#else
void SetOwner() {
latest_owner_ = pthread_self();
is_owned_ = true;
}
void ClearOwner() { is_owned_ = false; }
void AssertOwned() const {
RTC_CHECK(is_owned_);
RTC_CHECK(pthread_equal(latest_owner_, pthread_self()));
}
private:
// Use two separate primitive types, rather than absl::optional, since the
// data race described below might invalidate absl::optional invariants.
bool is_owned_ = false;
pthread_t latest_owner_ = pthread_self();
#endif
};
pthread_mutex_t mutex_;
// This record is modified only with the mutex held, and hence, calls to
// AssertHeld where mutex is held are race-free and will always succeed.
//
// The failure case is more subtle: If AssertHeld is called from some thread
// not holding the mutex, and RTC_DCHECK_IS_ON==1, we have a data race. It is
// highly likely that the calling thread will see `is_owned_` false or
// `latest_owner_` different from itself, and crash. But it may fail to crash,
// and invoke some other undefined behavior (still, this race can happen only
// when RTC_DCHECK_IS_ON==1).
RTC_NO_UNIQUE_ADDRESS OwnerRecord owner_;
};
} // namespace webrtc
#endif // #if defined(WEBRTC_POSIX)
#endif // RTC_BASE_SYNCHRONIZATION_MUTEX_PTHREAD_H_
|
