// 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 <utility>
|
|
#include "base/bind.h"
|
#include "base/lazy_instance.h"
|
#include "base/logging.h"
|
#include "base/memory/ptr_util.h"
|
#include "base/run_loop.h"
|
#include "base/threading/sequenced_task_runner_handle.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
|
scoped_refptr<SingleThreadTaskRunner> ThreadTaskRunnerHandle::Get() {
|
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).";
|
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
|
// being set (but SequencedTaskRunnerHandle::IsSet() includes
|
// ThreadTaskRunnerHandle::IsSet() so that's discounted as the only valid
|
// excuse for it to be true). Sadly this means that tests that merely need a
|
// SequencedTaskRunnerHandle on their main thread can be forced to use a
|
// ThreadTaskRunnerHandle if they're also using test task runners (that
|
// OverrideForTesting() when running their tasks from said main thread). To
|
// solve this: sequence_task_runner_handle.cc and thread_task_runner_handle.cc
|
// would have to be merged into a single impl file and share TLS state. This
|
// was deemed unecessary for now as most tests should use higher level
|
// constructs and not have to instantiate task runner handles on their own.
|
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->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->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)) {
|
DCHECK(task_runner_->BelongsToCurrentThread());
|
// No SequencedTaskRunnerHandle (which includes ThreadTaskRunnerHandles)
|
// should already be set for this thread.
|
DCHECK(!SequencedTaskRunnerHandle::IsSet());
|
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
|
