| // Copyright 2015 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_COMMON_POLLABLE_THREAD_SAFE_FLAG_H_ |
| #define THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_COMMON_POLLABLE_THREAD_SAFE_FLAG_H_ |
| |
| #include "base/atomicops.h" |
| #include "base/macros.h" |
| #include "base/synchronization/lock.h" |
| |
| // A PollableThreadSafeFlag can be polled without requiring a lock, but can only |
| // be updated if a lock is held. This enables lock-free checking as to whether a |
| // condition has changed, while protecting operations which update the condition |
| // with a lock. You must ensure that the flag is only updated within the same |
| // lock-protected critical section as any other variables on which the condition |
| // depends. |
| class PollableThreadSafeFlag { |
| public: |
| explicit PollableThreadSafeFlag(base::Lock* write_lock); |
| ~PollableThreadSafeFlag(); |
| |
| // Set the flag. May only be called if |write_lock| is held. |
| void SetWhileLocked(bool value); |
| |
| // Returns true iff the flag is set to true. |
| bool IsSet() const; |
| |
| private: |
| base::subtle::Atomic32 flag_; |
| base::Lock* write_lock_; // Not owned. |
| |
| DISALLOW_COPY_AND_ASSIGN(PollableThreadSafeFlag); |
| }; |
| |
| #endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_COMMON_POLLABLE_THREAD_SAFE_FLAG_H_ |