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1 // Copyright 2015 The Chromium Authors. All rights reserved. | 1 // Copyright 2015 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 #ifndef COMPONENTS_SCHEDULER_BASE_POLLABLE_THREAD_SAFE_FLAG_H_ | 5 #ifndef COMPONENTS_SCHEDULER_BASE_POLLABLE_THREAD_SAFE_FLAG_H_ |
6 #define COMPONENTS_SCHEDULER_BASE_POLLABLE_THREAD_SAFE_FLAG_H_ | 6 #define COMPONENTS_SCHEDULER_BASE_POLLABLE_THREAD_SAFE_FLAG_H_ |
7 | 7 |
8 #include "base/atomicops.h" | 8 #include "base/atomicops.h" |
| 9 #include "base/macros.h" |
9 #include "base/synchronization/lock.h" | 10 #include "base/synchronization/lock.h" |
10 | 11 |
11 // A PollableThreadSafeFlag can be polled without requiring a lock, but can only | 12 // A PollableThreadSafeFlag can be polled without requiring a lock, but can only |
12 // be updated if a lock is held. This enables lock-free checking as to whether a | 13 // be updated if a lock is held. This enables lock-free checking as to whether a |
13 // condition has changed, while protecting operations which update the condition | 14 // condition has changed, while protecting operations which update the condition |
14 // with a lock. You must ensure that the flag is only updated within the same | 15 // with a lock. You must ensure that the flag is only updated within the same |
15 // lock-protected critical section as any other variables on which the condition | 16 // lock-protected critical section as any other variables on which the condition |
16 // depends. | 17 // depends. |
17 class PollableThreadSafeFlag { | 18 class PollableThreadSafeFlag { |
18 public: | 19 public: |
19 explicit PollableThreadSafeFlag(base::Lock* write_lock); | 20 explicit PollableThreadSafeFlag(base::Lock* write_lock); |
20 ~PollableThreadSafeFlag(); | 21 ~PollableThreadSafeFlag(); |
21 | 22 |
22 // Set the flag. May only be called if |write_lock| is held. | 23 // Set the flag. May only be called if |write_lock| is held. |
23 void SetWhileLocked(bool value); | 24 void SetWhileLocked(bool value); |
24 | 25 |
25 // Returns true iff the flag is set to true. | 26 // Returns true iff the flag is set to true. |
26 bool IsSet() const; | 27 bool IsSet() const; |
27 | 28 |
28 private: | 29 private: |
29 base::subtle::Atomic32 flag_; | 30 base::subtle::Atomic32 flag_; |
30 base::Lock* write_lock_; // Not owned. | 31 base::Lock* write_lock_; // Not owned. |
31 | 32 |
32 DISALLOW_COPY_AND_ASSIGN(PollableThreadSafeFlag); | 33 DISALLOW_COPY_AND_ASSIGN(PollableThreadSafeFlag); |
33 }; | 34 }; |
34 | 35 |
35 #endif // COMPONENTS_SCHEDULER_BASE_POLLABLE_THREAD_SAFE_FLAG_H_ | 36 #endif // COMPONENTS_SCHEDULER_BASE_POLLABLE_THREAD_SAFE_FLAG_H_ |
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