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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_TASK_COMMON_SCOPED_DEFER_TASK_POSTING_H_
#define BASE_TASK_COMMON_SCOPED_DEFER_TASK_POSTING_H_
#include <vector>
#include "base/base_export.h"
#include "base/location.h"
#include "base/task/sequenced_task_runner.h"
#include "base/time/time.h"
namespace base {
// Tracing wants to post tasks from within a trace event within PostTask, but
// this can lead to a deadlock. Create a scope to ensure that we are posting
// the tasks in question outside of the scope of the lock.
// NOTE: This scope affects only the thread it is created on. All other threads
// still can post tasks.
//
// TODO(altimin): It should be possible to get rid of this scope, but this
// requires refactoring TimeDomain to ensure that TimeDomain never changes and
// we can read current time without grabbing a lock.
class BASE_EXPORT [[maybe_unused, nodiscard]] ScopedDeferTaskPosting {
public:
static void PostOrDefer(scoped_refptr<SequencedTaskRunner> task_runner,
const Location& from_here,
OnceClosure task,
base::TimeDelta delay);
static bool IsPresent();
ScopedDeferTaskPosting();
ScopedDeferTaskPosting(const ScopedDeferTaskPosting&) = delete;
ScopedDeferTaskPosting& operator=(const ScopedDeferTaskPosting&) = delete;
~ScopedDeferTaskPosting();
private:
static ScopedDeferTaskPosting* Get();
// Returns whether the |scope| was set as active, which happens only
// when the scope wasn't set before.
static bool Set(ScopedDeferTaskPosting* scope);
void DeferTaskPosting(scoped_refptr<SequencedTaskRunner> task_runner,
const Location& from_here,
OnceClosure task,
base::TimeDelta delay);
struct DeferredTask {
DeferredTask(scoped_refptr<SequencedTaskRunner> task_runner,
Location from_here,
OnceClosure task,
base::TimeDelta delay);
DeferredTask(const DeferredTask&) = delete;
DeferredTask& operator=(const DeferredTask&) = delete;
DeferredTask(DeferredTask&& task);
~DeferredTask();
scoped_refptr<SequencedTaskRunner> task_runner;
Location from_here;
OnceClosure task;
base::TimeDelta delay;
};
std::vector<DeferredTask> deferred_tasks_;
// Scopes can be nested (e.g. ScheduleWork inside PostTasks can post a task
// to another task runner), so we want to know whether the scope is top-level
// or not.
bool top_level_scope_ = false;
};
} // namespace base
#endif // BASE_TASK_COMMON_SCOPED_DEFER_TASK_POSTING_H_
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