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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef GPU_COMMAND_BUFFER_SERVICE_RETAINING_ONE_SHOT_TIMER_HOLDER_H_
#define GPU_COMMAND_BUFFER_SERVICE_RETAINING_ONE_SHOT_TIMER_HOLDER_H_
#include <memory>
#include "base/functional/callback.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/lock.h"
#include "base/thread_annotations.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "gpu/command_buffer/service/gpu_command_buffer_service_export.h"
namespace base {
class SingleThreadTaskRunner;
}
namespace gpu {
// This class holds a RetainingOneShotTimer and ensures thread safety.
// The public methods are safe to call from any threads.
// Before the object is destructed, DestroyTimer() must be called to clean up.
class GPU_COMMAND_BUFFER_SERVICE_EXPORT RetainingOneShotTimerHolder
: public base::RefCountedThreadSafe<RetainingOneShotTimerHolder> {
public:
// `max_delay` and `min_delay` together specify how ResetTimerIfNecessary()
// sets up the timer to fire. Please see comments of that method.
//
// `task_runner` is the runner on which the timer operates and destructs.
// `user_task` is called on `task_runner` whenever the timer is fired.
//
// Note: To avoid race between `user_task` execution and clean up in
// DestroyTimer(), `user_task` is run while holding `lock_`. Therefore:
// - `user_task` must not call into DestroyTimer();
// - if `user_task` holds certain locks, in order to avoid lock order
// inversion, callers must not call DestroyTimer() under those locks.
RetainingOneShotTimerHolder(
base::TimeDelta max_delay,
base::TimeDelta min_delay,
scoped_refptr<base::SingleThreadTaskRunner> task_runner,
base::RepeatingClosure user_task);
RetainingOneShotTimerHolder(const RetainingOneShotTimerHolder& other) =
delete;
RetainingOneShotTimerHolder& operator=(
const RetainingOneShotTimerHolder& other) = delete;
// If the timer is already running and the remaining time is between
// `max_delay` and `min_delay`, then it is a no-op; otherwise, the timer is
// reset to first after `max_delay`.
void ResetTimerIfNecessary();
// Destroys the timer. Once the method returns, it guarantees that
// `user_task_` won't be called afterwards. This method will block if
// `user_task_` is being called.
//
// This method must be called to clean up.
void DestroyTimer() LOCKS_EXCLUDED(lock_);
private:
friend class base::RefCountedThreadSafe<RetainingOneShotTimerHolder>;
~RetainingOneShotTimerHolder();
void DestroyTimerOnTaskRunner();
void OnTimerFired() LOCKS_EXCLUDED(lock_);
const base::TimeDelta min_delay_;
scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
mutable base::Lock lock_;
base::RepeatingClosure user_task_ GUARDED_BY(lock_);
// Operates exclusively on `task_runner_`.
std::unique_ptr<base::RetainingOneShotTimer> timer_;
};
} // namespace gpu
#endif // GPU_COMMAND_BUFFER_SERVICE_RETAINING_ONE_SHOT_TIMER_HOLDER_H_
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