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1 /*
2  *  Copyright 2004 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 WEBRTC_BASE_CRITICALSECTION_H__
12 #define WEBRTC_BASE_CRITICALSECTION_H__
13 
14 #include "webrtc/base/constructormagic.h"
15 #include "webrtc/base/thread_annotations.h"
16 
17 #if defined(WEBRTC_WIN)
18 #include "webrtc/base/win32.h"
19 #endif
20 
21 #if defined(WEBRTC_POSIX)
22 #include <pthread.h>
23 #endif
24 
25 #ifdef _DEBUG
26 #define CS_TRACK_OWNER 1
27 #endif  // _DEBUG
28 
29 #if CS_TRACK_OWNER
30 #define TRACK_OWNER(x) x
31 #else  // !CS_TRACK_OWNER
32 #define TRACK_OWNER(x)
33 #endif  // !CS_TRACK_OWNER
34 
35 namespace rtc {
36 
37 #if defined(WEBRTC_WIN)
38 class LOCKABLE CriticalSection {
39  public:
CriticalSection()40   CriticalSection() {
41     InitializeCriticalSection(&crit_);
42     // Windows docs say 0 is not a valid thread id
43     TRACK_OWNER(thread_ = 0);
44   }
~CriticalSection()45   ~CriticalSection() {
46     DeleteCriticalSection(&crit_);
47   }
Enter()48   void Enter() EXCLUSIVE_LOCK_FUNCTION() {
49     EnterCriticalSection(&crit_);
50     TRACK_OWNER(thread_ = GetCurrentThreadId());
51   }
TryEnter()52   bool TryEnter() EXCLUSIVE_TRYLOCK_FUNCTION(true) {
53     if (TryEnterCriticalSection(&crit_) != FALSE) {
54       TRACK_OWNER(thread_ = GetCurrentThreadId());
55       return true;
56     }
57     return false;
58   }
Leave()59   void Leave() UNLOCK_FUNCTION() {
60     TRACK_OWNER(thread_ = 0);
61     LeaveCriticalSection(&crit_);
62   }
63 
64 #if CS_TRACK_OWNER
CurrentThreadIsOwner()65   bool CurrentThreadIsOwner() const { return thread_ == GetCurrentThreadId(); }
66 #endif  // CS_TRACK_OWNER
67 
68  private:
69   CRITICAL_SECTION crit_;
70   TRACK_OWNER(DWORD thread_);  // The section's owning thread id
71 };
72 #endif // WEBRTC_WIN
73 
74 #if defined(WEBRTC_POSIX)
75 class LOCKABLE CriticalSection {
76  public:
CriticalSection()77   CriticalSection() {
78     pthread_mutexattr_t mutex_attribute;
79     pthread_mutexattr_init(&mutex_attribute);
80     pthread_mutexattr_settype(&mutex_attribute, PTHREAD_MUTEX_RECURSIVE);
81     pthread_mutex_init(&mutex_, &mutex_attribute);
82     pthread_mutexattr_destroy(&mutex_attribute);
83     TRACK_OWNER(thread_ = 0);
84   }
~CriticalSection()85   ~CriticalSection() {
86     pthread_mutex_destroy(&mutex_);
87   }
Enter()88   void Enter() EXCLUSIVE_LOCK_FUNCTION() {
89     pthread_mutex_lock(&mutex_);
90     TRACK_OWNER(thread_ = pthread_self());
91   }
TryEnter()92   bool TryEnter() EXCLUSIVE_TRYLOCK_FUNCTION(true) {
93     if (pthread_mutex_trylock(&mutex_) == 0) {
94       TRACK_OWNER(thread_ = pthread_self());
95       return true;
96     }
97     return false;
98   }
Leave()99   void Leave() UNLOCK_FUNCTION() {
100     TRACK_OWNER(thread_ = 0);
101     pthread_mutex_unlock(&mutex_);
102   }
103 
104 #if CS_TRACK_OWNER
CurrentThreadIsOwner()105   bool CurrentThreadIsOwner() const { return pthread_equal(thread_, pthread_self()); }
106 #endif  // CS_TRACK_OWNER
107 
108  private:
109   pthread_mutex_t mutex_;
110   TRACK_OWNER(pthread_t thread_);
111 };
112 #endif // WEBRTC_POSIX
113 
114 // CritScope, for serializing execution through a scope.
115 class SCOPED_LOCKABLE CritScope {
116  public:
CritScope(CriticalSection * pcrit)117   explicit CritScope(CriticalSection *pcrit) EXCLUSIVE_LOCK_FUNCTION(pcrit) {
118     pcrit_ = pcrit;
119     pcrit_->Enter();
120   }
UNLOCK_FUNCTION()121   ~CritScope() UNLOCK_FUNCTION() {
122     pcrit_->Leave();
123   }
124  private:
125   CriticalSection *pcrit_;
126   DISALLOW_COPY_AND_ASSIGN(CritScope);
127 };
128 
129 // Tries to lock a critical section on construction via
130 // CriticalSection::TryEnter, and unlocks on destruction if the
131 // lock was taken. Never blocks.
132 //
133 // IMPORTANT: Unlike CritScope, the lock may not be owned by this thread in
134 // subsequent code. Users *must* check locked() to determine if the
135 // lock was taken. If you're not calling locked(), you're doing it wrong!
136 class TryCritScope {
137  public:
TryCritScope(CriticalSection * pcrit)138   explicit TryCritScope(CriticalSection *pcrit) {
139     pcrit_ = pcrit;
140     locked_ = pcrit_->TryEnter();
141   }
~TryCritScope()142   ~TryCritScope() {
143     if (locked_) {
144       pcrit_->Leave();
145     }
146   }
locked()147   bool locked() const {
148     return locked_;
149   }
150  private:
151   CriticalSection *pcrit_;
152   bool locked_;
153   DISALLOW_COPY_AND_ASSIGN(TryCritScope);
154 };
155 
156 // TODO: Move this to atomicops.h, which can't be done easily because of
157 // complex compile rules.
158 class AtomicOps {
159  public:
160 #if defined(WEBRTC_WIN)
161   // Assumes sizeof(int) == sizeof(LONG), which it is on Win32 and Win64.
Increment(int * i)162   static int Increment(int* i) {
163     return ::InterlockedIncrement(reinterpret_cast<LONG*>(i));
164   }
Decrement(int * i)165   static int Decrement(int* i) {
166     return ::InterlockedDecrement(reinterpret_cast<LONG*>(i));
167   }
168 #else
169   static int Increment(int* i) {
170     return __sync_add_and_fetch(i, 1);
171   }
172   static int Decrement(int* i) {
173     return __sync_sub_and_fetch(i, 1);
174   }
175 #endif
176 };
177 
178 } // namespace rtc
179 
180 #endif // WEBRTC_BASE_CRITICALSECTION_H__
181