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 3 // found in the LICENSE file. 4 5 #ifndef BASE_SYNCHRONIZATION_CANCELLATION_FLAG_H_ 6 #define BASE_SYNCHRONIZATION_CANCELLATION_FLAG_H_ 7 8 #include "base/atomicops.h" 9 #include "base/base_export.h" 10 #include "base/macros.h" 11 #include "base/threading/platform_thread.h" 12 13 namespace base { 14 15 // CancellationFlag allows one thread to cancel jobs executed on some worker 16 // thread. Calling Set() from one thread and IsSet() from a number of threads 17 // is thread-safe. 18 // 19 // This class IS NOT intended for synchronization between threads. 20 class BASE_EXPORT CancellationFlag { 21 public: CancellationFlag()22 CancellationFlag() : flag_(false) { 23 #if !defined(NDEBUG) 24 set_on_ = PlatformThread::CurrentId(); 25 #endif 26 } ~CancellationFlag()27 ~CancellationFlag() {} 28 29 // Set the flag. May only be called on the thread which owns the object. 30 void Set(); 31 bool IsSet() const; // Returns true iff the flag was set. 32 33 // For subtle reasons that may be different on different architectures, 34 // a different thread testing IsSet() may erroneously read 'true' after 35 // this method has been called. 36 void UnsafeResetForTesting(); 37 38 private: 39 base::subtle::Atomic32 flag_; 40 #if !defined(NDEBUG) 41 PlatformThreadId set_on_; 42 #endif 43 44 DISALLOW_COPY_AND_ASSIGN(CancellationFlag); 45 }; 46 47 } // namespace base 48 49 #endif // BASE_SYNCHRONIZATION_CANCELLATION_FLAG_H_ 50