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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // ConditionVariable wraps pthreads condition variable synchronization or, on | 5 // ConditionVariable wraps pthreads condition variable synchronization or, on |
6 // Windows, simulates it. This functionality is very helpful for having | 6 // Windows, simulates it. This functionality is very helpful for having |
7 // several threads wait for an event, as is common with a thread pool managed | 7 // several threads wait for an event, as is common with a thread pool managed |
8 // by a master. The meaning of such an event in the (worker) thread pool | 8 // by a master. The meaning of such an event in the (worker) thread pool |
9 // scenario is that additional tasks are now available for processing. It is | 9 // scenario is that additional tasks are now available for processing. It is |
10 // used in Chrome in the DNS prefetching system to notify worker threads that | 10 // used in Chrome in the DNS prefetching system to notify worker threads that |
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68 #include "base/base_export.h" | 68 #include "base/base_export.h" |
69 #include "base/logging.h" | 69 #include "base/logging.h" |
70 #include "base/macros.h" | 70 #include "base/macros.h" |
71 #include "base/synchronization/lock.h" | 71 #include "base/synchronization/lock.h" |
72 #include "build/build_config.h" | 72 #include "build/build_config.h" |
73 | 73 |
74 #if defined(OS_POSIX) | 74 #if defined(OS_POSIX) |
75 #include <pthread.h> | 75 #include <pthread.h> |
76 #endif | 76 #endif |
77 | 77 |
| 78 #if defined(OS_WIN) |
| 79 #include <windows.h> |
| 80 #endif |
| 81 |
78 namespace base { | 82 namespace base { |
79 | 83 |
80 class ConditionVarImpl; | |
81 class TimeDelta; | 84 class TimeDelta; |
82 | 85 |
83 class BASE_EXPORT ConditionVariable { | 86 class BASE_EXPORT ConditionVariable { |
84 public: | 87 public: |
85 // Construct a cv for use with ONLY one user lock. | 88 // Construct a cv for use with ONLY one user lock. |
86 explicit ConditionVariable(Lock* user_lock); | 89 explicit ConditionVariable(Lock* user_lock); |
87 | 90 |
88 ~ConditionVariable(); | 91 ~ConditionVariable(); |
89 | 92 |
90 // Wait() releases the caller's critical section atomically as it starts to | 93 // Wait() releases the caller's critical section atomically as it starts to |
91 // sleep, and the reacquires it when it is signaled. | 94 // sleep, and the reacquires it when it is signaled. |
92 void Wait(); | 95 void Wait(); |
93 void TimedWait(const TimeDelta& max_time); | 96 void TimedWait(const TimeDelta& max_time); |
94 | 97 |
95 // Broadcast() revives all waiting threads. | 98 // Broadcast() revives all waiting threads. |
96 void Broadcast(); | 99 void Broadcast(); |
97 // Signal() revives one waiting thread. | 100 // Signal() revives one waiting thread. |
98 void Signal(); | 101 void Signal(); |
99 | 102 |
100 private: | 103 private: |
101 | 104 |
102 #if defined(OS_WIN) | 105 #if defined(OS_WIN) |
103 ConditionVarImpl* impl_; | 106 CONDITION_VARIABLE cv_; |
| 107 CRITICAL_SECTION* const crit_sec_; |
104 #elif defined(OS_POSIX) | 108 #elif defined(OS_POSIX) |
105 pthread_cond_t condition_; | 109 pthread_cond_t condition_; |
106 pthread_mutex_t* user_mutex_; | 110 pthread_mutex_t* user_mutex_; |
107 #if DCHECK_IS_ON() | |
108 base::Lock* user_lock_; // Needed to adjust shadow lock state on wait. | |
109 #endif | 111 #endif |
110 | 112 |
| 113 #if DCHECK_IS_ON() && (defined(OS_WIN) || defined(OS_POSIX)) |
| 114 base::Lock* const user_lock_; // Needed to adjust shadow lock state on wait. |
111 #endif | 115 #endif |
112 | 116 |
113 DISALLOW_COPY_AND_ASSIGN(ConditionVariable); | 117 DISALLOW_COPY_AND_ASSIGN(ConditionVariable); |
114 }; | 118 }; |
115 | 119 |
116 } // namespace base | 120 } // namespace base |
117 | 121 |
118 #endif // BASE_SYNCHRONIZATION_CONDITION_VARIABLE_H_ | 122 #endif // BASE_SYNCHRONIZATION_CONDITION_VARIABLE_H_ |
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