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// Copyright 2016 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_task_runner_handle.h"
#include <memory>
#include <utility>
#include "base/bind.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/run_loop.h"
#include "base/threading/thread_local.h"
namespace base {
namespace {
base::LazyInstance<base::ThreadLocalPointer<ThreadTaskRunnerHandle>>::Leaky
thread_task_runner_tls = LAZY_INSTANCE_INITIALIZER;
} // namespace
// static
const scoped_refptr<SingleThreadTaskRunner>& ThreadTaskRunnerHandle::Get() {
const ThreadTaskRunnerHandle* current =
thread_task_runner_tls.Pointer()->Get();
CHECK(current)
<< "Error: This caller requires a single-threaded context (i.e. the "
"current task needs to run from a SingleThreadTaskRunner). If you're "
"in a test refer to //docs/threading_and_tasks_testing.md.";
return current->task_runner_;
}
// static
bool ThreadTaskRunnerHandle::IsSet() {
return !!thread_task_runner_tls.Pointer()->Get();
}
// static
ScopedClosureRunner ThreadTaskRunnerHandle::OverrideForTesting(
scoped_refptr<SingleThreadTaskRunner> overriding_task_runner) {
// OverrideForTesting() is not compatible with a SequencedTaskRunnerHandle
// already being set on this thread (except when it's set by the current
// ThreadTaskRunnerHandle).
DCHECK(!SequencedTaskRunnerHandle::IsSet() || IsSet());
if (!IsSet()) {
auto top_level_ttrh = std::make_unique<ThreadTaskRunnerHandle>(
std::move(overriding_task_runner));
return ScopedClosureRunner(base::BindOnce(
[](std::unique_ptr<ThreadTaskRunnerHandle> ttrh_to_release) {},
std::move(top_level_ttrh)));
}
ThreadTaskRunnerHandle* ttrh = thread_task_runner_tls.Pointer()->Get();
// Swap the two (and below bind |overriding_task_runner|, which is now the
// previous one, as the |task_runner_to_restore|).
ttrh->sequenced_task_runner_handle_.task_runner_ = overriding_task_runner;
ttrh->task_runner_.swap(overriding_task_runner);
auto no_running_during_override =
std::make_unique<RunLoop::ScopedDisallowRunningForTesting>();
return ScopedClosureRunner(base::BindOnce(
[](scoped_refptr<SingleThreadTaskRunner> task_runner_to_restore,
SingleThreadTaskRunner* expected_task_runner_before_restore,
std::unique_ptr<RunLoop::ScopedDisallowRunningForTesting>
no_running_during_override) {
ThreadTaskRunnerHandle* ttrh = thread_task_runner_tls.Pointer()->Get();
DCHECK_EQ(expected_task_runner_before_restore, ttrh->task_runner_.get())
<< "Nested overrides must expire their ScopedClosureRunners "
"in LIFO order.";
ttrh->sequenced_task_runner_handle_.task_runner_ =
task_runner_to_restore;
ttrh->task_runner_.swap(task_runner_to_restore);
},
std::move(overriding_task_runner),
base::Unretained(ttrh->task_runner_.get()),
std::move(no_running_during_override)));
}
ThreadTaskRunnerHandle::ThreadTaskRunnerHandle(
scoped_refptr<SingleThreadTaskRunner> task_runner)
: task_runner_(std::move(task_runner)),
sequenced_task_runner_handle_(task_runner_) {
DCHECK(task_runner_->BelongsToCurrentThread());
DCHECK(!thread_task_runner_tls.Pointer()->Get());
thread_task_runner_tls.Pointer()->Set(this);
}
ThreadTaskRunnerHandle::~ThreadTaskRunnerHandle() {
DCHECK(task_runner_->BelongsToCurrentThread());
DCHECK_EQ(thread_task_runner_tls.Pointer()->Get(), this);
thread_task_runner_tls.Pointer()->Set(nullptr);
}
} // namespace base
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