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