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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/sequence_checker_impl.h"
#include <utility>
#include "base/check.h"
#include "base/compiler_specific.h"
#include "base/debug/stack_trace.h"
#include "base/memory/ptr_util.h"
#include "base/sequence_token.h"
#include "base/threading/thread_checker.h"
#include "base/threading/thread_checker_impl.h"
#include "base/threading/thread_local_storage.h"
namespace base {
// static
void SequenceCheckerImpl::EnableStackLogging() {
ThreadChecker::EnableStackLogging();
}
SequenceCheckerImpl::SequenceCheckerImpl() = default;
SequenceCheckerImpl::~SequenceCheckerImpl() = default;
SequenceCheckerImpl::SequenceCheckerImpl(SequenceCheckerImpl&& other) = default;
SequenceCheckerImpl& SequenceCheckerImpl::operator=(
SequenceCheckerImpl&& other) = default;
bool SequenceCheckerImpl::CalledOnValidSequence(
std::unique_ptr<debug::StackTrace>* bound_at) const {
AutoLock auto_lock(thread_checker_.lock_);
// When `sequence_token_` or SequenceToken::GetForCurrentThread() are
// invalid fall back on ThreadChecker. We assume that SequenceChecker things
// are mostly run on a sequence and that that is the correct sequence (hence
// using LIKELY annotation).
if (LIKELY(thread_checker_.sequence_token_.IsValid())) {
if (LIKELY(thread_checker_.sequence_token_ ==
SequenceToken::GetForCurrentThread())) {
return true;
}
// TODO(pbos): This preserves existing behavior that `sequence_token_` is
// ignored after TLS shutdown. It should either be documented here why
// that is necessary (shouldn't this destroy on sequence?) or
// SequenceCheckerTest.CalledOnValidSequenceFromThreadDestruction should
// be updated to reflect the expected behavior.
//
// crrev.com/682023 added this TLS-check to solve an edge case but that
// edge case was probably only a problem before TLS-destruction order was
// fixed in crrev.com/1119244. crrev.com/1117059 further improved
// TLS-destruction order of tokens by using `thread_local` and making it
// deterministic.
// See https://timsong-cpp.github.io/cppwp/n4140/basic.start.term: "If the
// completion of the constructor or dynamic initialization of an object
// with thread storage duration is sequenced before that of another, the
// completion of the destructor of the second is sequenced before the
// initiation of the destructor of the first."
if (!ThreadLocalStorage::HasBeenDestroyed()) {
if (bound_at) {
*bound_at = thread_checker_.GetBoundAt();
}
return false;
}
}
// SequenceChecker behaves as a ThreadChecker when it is not bound to a
// valid sequence token.
return thread_checker_.CalledOnValidThreadInternal(bound_at);
}
void SequenceCheckerImpl::DetachFromSequence() {
thread_checker_.DetachFromThread();
}
} // namespace base
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