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// 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 "base/logging.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<subtle::Atomic32>(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
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