1 // Copyright (c) 2010 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 #include "base/threading/thread_collision_warner.h" 6 7 #include "base/logging.h" 8 #include "base/threading/platform_thread.h" 9 10 namespace base { 11 12 void DCheckAsserter::warn() { 13 NOTREACHED() << "Thread Collision"; 14 } 15 16 static subtle::Atomic32 CurrentThread() { 17 const PlatformThreadId current_thread_id = PlatformThread::CurrentId(); 18 // We need to get the thread id into an atomic data type. This might be a 19 // truncating conversion, but any loss-of-information just increases the 20 // chance of a fault negative, not a false positive. 21 const subtle::Atomic32 atomic_thread_id = 22 static_cast<subtle::Atomic32>(current_thread_id); 23 24 return atomic_thread_id; 25 } 26 27 void ThreadCollisionWarner::EnterSelf() { 28 // If the active thread is 0 then I'll write the current thread ID 29 // if two or more threads arrive here only one will succeed to 30 // write on valid_thread_id_ the current thread ID. 31 subtle::Atomic32 current_thread_id = CurrentThread(); 32 33 int previous_value = subtle::NoBarrier_CompareAndSwap(&valid_thread_id_, 34 0, 35 current_thread_id); 36 if (previous_value != 0 && previous_value != current_thread_id) { 37 // gotcha! a thread is trying to use the same class and that is 38 // not current thread. 39 asserter_->warn(); 40 } 41 42 subtle::NoBarrier_AtomicIncrement(&counter_, 1); 43 } 44 45 void ThreadCollisionWarner::Enter() { 46 subtle::Atomic32 current_thread_id = CurrentThread(); 47 48 if (subtle::NoBarrier_CompareAndSwap(&valid_thread_id_, 49 0, 50 current_thread_id) != 0) { 51 // gotcha! another thread is trying to use the same class. 52 asserter_->warn(); 53 } 54 55 subtle::NoBarrier_AtomicIncrement(&counter_, 1); 56 } 57 58 void ThreadCollisionWarner::Leave() { 59 if (subtle::Barrier_AtomicIncrement(&counter_, -1) == 0) { 60 subtle::NoBarrier_Store(&valid_thread_id_, 0); 61 } 62 } 63 64 } // namespace base 65
