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80 lines
2.8 KiB
C++
80 lines
2.8 KiB
C++
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// Copyright 2015 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/sequenced_task_runner_handle.h"
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#include <utility>
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#include "base/lazy_instance.h"
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#include "base/logging.h"
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#include "base/threading/sequenced_worker_pool.h"
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#include "base/threading/thread_local.h"
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#include "base/threading/thread_task_runner_handle.h"
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namespace base {
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namespace {
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LazyInstance<ThreadLocalPointer<SequencedTaskRunnerHandle>>::Leaky
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sequenced_task_runner_tls = LAZY_INSTANCE_INITIALIZER;
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} // namespace
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// static
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scoped_refptr<SequencedTaskRunner> SequencedTaskRunnerHandle::Get() {
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// Return the registered SequencedTaskRunner, if any.
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const SequencedTaskRunnerHandle* handle =
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sequenced_task_runner_tls.Pointer()->Get();
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if (handle) {
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// Various modes of setting SequencedTaskRunnerHandle don't combine.
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DCHECK(!SequencedWorkerPool::GetSequenceTokenForCurrentThread().IsValid());
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return handle->task_runner_;
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}
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// If we are on a worker thread for a SequencedWorkerPool that is running a
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// sequenced task, return a SequencedTaskRunner for it.
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scoped_refptr<SequencedWorkerPool> pool =
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SequencedWorkerPool::GetWorkerPoolForCurrentThread();
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if (pool) {
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SequencedWorkerPool::SequenceToken sequence_token =
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SequencedWorkerPool::GetSequenceTokenForCurrentThread();
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DCHECK(sequence_token.IsValid());
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scoped_refptr<SequencedTaskRunner> sequenced_task_runner(
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pool->GetSequencedTaskRunner(sequence_token));
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DCHECK(sequenced_task_runner->RunsTasksInCurrentSequence());
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return sequenced_task_runner;
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}
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// Note if you hit this: the problem is the lack of a sequenced context. The
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// ThreadTaskRunnerHandle is just the last attempt at finding such a context.
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CHECK(ThreadTaskRunnerHandle::IsSet())
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<< "Error: This caller requires a sequenced context (i.e. the "
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"current task needs to run from a SequencedTaskRunner).";
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return ThreadTaskRunnerHandle::Get();
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}
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// static
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bool SequencedTaskRunnerHandle::IsSet() {
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return sequenced_task_runner_tls.Pointer()->Get() ||
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SequencedWorkerPool::GetSequenceTokenForCurrentThread().IsValid() ||
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ThreadTaskRunnerHandle::IsSet();
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}
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SequencedTaskRunnerHandle::SequencedTaskRunnerHandle(
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scoped_refptr<SequencedTaskRunner> task_runner)
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: task_runner_(std::move(task_runner)) {
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DCHECK(task_runner_->RunsTasksInCurrentSequence());
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DCHECK(!SequencedTaskRunnerHandle::IsSet());
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sequenced_task_runner_tls.Pointer()->Set(this);
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}
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SequencedTaskRunnerHandle::~SequencedTaskRunnerHandle() {
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DCHECK(task_runner_->RunsTasksInCurrentSequence());
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DCHECK_EQ(sequenced_task_runner_tls.Pointer()->Get(), this);
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sequenced_task_runner_tls.Pointer()->Set(nullptr);
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}
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} // namespace base
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