michael@0: // Copyright (c) 2010 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: #include "base/threading/thread_collision_warner.h"
michael@0: 
michael@0: #include "base/logging.h"
michael@0: #include "base/threading/platform_thread.h"
michael@0: 
michael@0: namespace base {
michael@0: 
michael@0: void DCheckAsserter::warn() {
michael@0:   NOTREACHED() << "Thread Collision";
michael@0: }
michael@0: 
michael@0: static subtle::Atomic32 CurrentThread() {
michael@0:   const PlatformThreadId current_thread_id = PlatformThread::CurrentId();
michael@0:   // We need to get the thread id into an atomic data type. This might be a
michael@0:   // truncating conversion, but any loss-of-information just increases the
michael@0:   // chance of a fault negative, not a false positive.
michael@0:   const subtle::Atomic32 atomic_thread_id =
michael@0:       static_cast<subtle::Atomic32>(current_thread_id);
michael@0: 
michael@0:   return atomic_thread_id;
michael@0: }
michael@0: 
michael@0: void ThreadCollisionWarner::EnterSelf() {
michael@0:   // If the active thread is 0 then I'll write the current thread ID
michael@0:   // if two or more threads arrive here only one will succeed to
michael@0:   // write on valid_thread_id_ the current thread ID.
michael@0:   subtle::Atomic32 current_thread_id = CurrentThread();
michael@0: 
michael@0:   int previous_value = subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
michael@0:                                                         0,
michael@0:                                                         current_thread_id);
michael@0:   if (previous_value != 0 && previous_value != current_thread_id) {
michael@0:     // gotcha! a thread is trying to use the same class and that is
michael@0:     // not current thread.
michael@0:     asserter_->warn();
michael@0:   }
michael@0: 
michael@0:   subtle::NoBarrier_AtomicIncrement(&counter_, 1);
michael@0: }
michael@0: 
michael@0: void ThreadCollisionWarner::Enter() {
michael@0:   subtle::Atomic32 current_thread_id = CurrentThread();
michael@0: 
michael@0:   if (subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
michael@0:                                        0,
michael@0:                                        current_thread_id) != 0) {
michael@0:     // gotcha! another thread is trying to use the same class.
michael@0:     asserter_->warn();
michael@0:   }
michael@0: 
michael@0:   subtle::NoBarrier_AtomicIncrement(&counter_, 1);
michael@0: }
michael@0: 
michael@0: void ThreadCollisionWarner::Leave() {
michael@0:   if (subtle::Barrier_AtomicIncrement(&counter_, -1) == 0) {
michael@0:     subtle::NoBarrier_Store(&valid_thread_id_, 0);
michael@0:   }
michael@0: }
michael@0: 
michael@0: }  // namespace base