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