1 /*
2 * Copyright 2019 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 #include "rtc_base/synchronization/sequence_checker.h"
11
12 #if defined(WEBRTC_MAC)
13 #include <dispatch/dispatch.h>
14 #endif
15
16 #include "rtc_base/strings/string_builder.h"
17
18 namespace webrtc {
19 namespace {
20 // On Mac, returns the label of the current dispatch queue; elsewhere, return
21 // null.
GetSystemQueueRef()22 const void* GetSystemQueueRef() {
23 #if defined(WEBRTC_MAC)
24 return dispatch_queue_get_label(DISPATCH_CURRENT_QUEUE_LABEL);
25 #else
26 return nullptr;
27 #endif
28 }
29
30 } // namespace
31
ExpectationToString(const webrtc::SequenceChecker * checker)32 std::string ExpectationToString(const webrtc::SequenceChecker* checker) {
33 #if RTC_DCHECK_IS_ON
34 return checker->ExpectationToString();
35 #endif
36 return std::string();
37 }
38
SequenceCheckerImpl()39 SequenceCheckerImpl::SequenceCheckerImpl()
40 : attached_(true),
41 valid_thread_(rtc::CurrentThreadRef()),
42 valid_queue_(TaskQueueBase::Current()),
43 valid_system_queue_(GetSystemQueueRef()) {}
44
45 SequenceCheckerImpl::~SequenceCheckerImpl() = default;
46
IsCurrent() const47 bool SequenceCheckerImpl::IsCurrent() const {
48 const TaskQueueBase* const current_queue = TaskQueueBase::Current();
49 const rtc::PlatformThreadRef current_thread = rtc::CurrentThreadRef();
50 const void* const current_system_queue = GetSystemQueueRef();
51 MutexLock scoped_lock(&lock_);
52 if (!attached_) { // Previously detached.
53 attached_ = true;
54 valid_thread_ = current_thread;
55 valid_queue_ = current_queue;
56 valid_system_queue_ = current_system_queue;
57 return true;
58 }
59 if (valid_queue_ || current_queue) {
60 return valid_queue_ == current_queue;
61 }
62 if (valid_system_queue_ && valid_system_queue_ == current_system_queue) {
63 return true;
64 }
65 return rtc::IsThreadRefEqual(valid_thread_, current_thread);
66 }
67
Detach()68 void SequenceCheckerImpl::Detach() {
69 MutexLock scoped_lock(&lock_);
70 attached_ = false;
71 // We don't need to touch the other members here, they will be
72 // reset on the next call to IsCurrent().
73 }
74
75 #if RTC_DCHECK_IS_ON
ExpectationToString() const76 std::string SequenceCheckerImpl::ExpectationToString() const {
77 const TaskQueueBase* const current_queue = TaskQueueBase::Current();
78 const rtc::PlatformThreadRef current_thread = rtc::CurrentThreadRef();
79 const void* const current_system_queue = GetSystemQueueRef();
80 MutexLock scoped_lock(&lock_);
81 if (!attached_)
82 return "Checker currently not attached.";
83
84 // The format of the string is meant to compliment the one we have inside of
85 // FatalLog() (checks.cc). Example:
86 //
87 // # Expected: TQ: 0x0 SysQ: 0x7fff69541330 Thread: 0x11dcf6dc0
88 // # Actual: TQ: 0x7fa8f0604190 SysQ: 0x7fa8f0604a30 Thread: 0x700006f1a000
89 // TaskQueue doesn't match
90
91 rtc::StringBuilder message;
92 message.AppendFormat(
93 "# Expected: TQ: %p SysQ: %p Thread: %p\n"
94 "# Actual: TQ: %p SysQ: %p Thread: %p\n",
95 valid_queue_, valid_system_queue_,
96 reinterpret_cast<const void*>(valid_thread_), current_queue,
97 current_system_queue, reinterpret_cast<const void*>(current_thread));
98
99 if ((valid_queue_ || current_queue) && valid_queue_ != current_queue) {
100 message << "TaskQueue doesn't match\n";
101 } else if (valid_system_queue_ &&
102 valid_system_queue_ != current_system_queue) {
103 message << "System queue doesn't match\n";
104 } else if (!rtc::IsThreadRefEqual(valid_thread_, current_thread)) {
105 message << "Threads don't match\n";
106 }
107
108 return message.Release();
109 }
110 #endif // RTC_DCHECK_IS_ON
111
112 } // namespace webrtc
113