92 lines
3.0 KiB
C++
92 lines
3.0 KiB
C++
// Copyright (c) 2012 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/sequence_checker_impl.h"
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#include "base/logging.h"
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#include "base/memory/ptr_util.h"
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#include "base/sequence_token.h"
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#include "base/threading/thread_checker_impl.h"
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#include "base/threading/thread_local_storage.h"
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namespace base {
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class SequenceCheckerImpl::Core {
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public:
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Core() : sequence_token_(SequenceToken::GetForCurrentThread()) {}
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~Core() = default;
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bool CalledOnValidSequence() const {
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// SequenceToken::GetForCurrentThread() accesses thread-local storage.
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// During destruction the state of thread-local storage is not guaranteed to
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// be in a consistent state. Further, task-runner only installs the
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// SequenceToken when running a task. For this reason, |sequence_token_| is
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// not checked during thread destruction.
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if (!SequenceCheckerImpl::HasThreadLocalStorageBeenDestroyed() &&
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sequence_token_.IsValid()) {
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return sequence_token_ == SequenceToken::GetForCurrentThread();
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}
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// SequenceChecker behaves as a ThreadChecker when it is not bound to a
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// valid sequence token.
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return thread_checker_.CalledOnValidThread();
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}
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private:
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SequenceToken sequence_token_;
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// Used when |sequence_token_| is invalid, or during thread destruction.
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ThreadCheckerImpl thread_checker_;
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};
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SequenceCheckerImpl::SequenceCheckerImpl() : core_(std::make_unique<Core>()) {}
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SequenceCheckerImpl::~SequenceCheckerImpl() = default;
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SequenceCheckerImpl::SequenceCheckerImpl(SequenceCheckerImpl&& other) {
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// Verify that |other| is called on its associated sequence and bind it now if
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// it is currently detached (even if this isn't a DCHECK build).
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const bool other_called_on_valid_sequence = other.CalledOnValidSequence();
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DCHECK(other_called_on_valid_sequence);
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core_ = std::move(other.core_);
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}
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SequenceCheckerImpl& SequenceCheckerImpl::operator=(
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SequenceCheckerImpl&& other) {
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// If |this| is not in a detached state it needs to be bound to the current
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// sequence.
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DCHECK(CalledOnValidSequence());
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// Verify that |other| is called on its associated sequence and bind it now if
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// it is currently detached (even if this isn't a DCHECK build).
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const bool other_called_on_valid_sequence = other.CalledOnValidSequence();
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DCHECK(other_called_on_valid_sequence);
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// Intentionally not using either |lock_| in this method to let TSAN catch
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// racy assign.
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TS_UNCHECKED_READ(core_) = std::move(TS_UNCHECKED_READ(other.core_));
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return *this;
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}
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bool SequenceCheckerImpl::CalledOnValidSequence() const {
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AutoLock auto_lock(lock_);
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if (!core_)
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core_ = std::make_unique<Core>();
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return core_->CalledOnValidSequence();
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}
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void SequenceCheckerImpl::DetachFromSequence() {
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AutoLock auto_lock(lock_);
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core_.reset();
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}
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// static
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bool SequenceCheckerImpl::HasThreadLocalStorageBeenDestroyed() {
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return ThreadLocalStorage::HasBeenDestroyed();
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}
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} // namespace base
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