chromium/base/task/sequence_manager/work_deduplicator.h

// 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_SEQUENCE_MANAGER_WORK_DEDUPLICATOR_H_
#define BASE_TASK_SEQUENCE_MANAGER_WORK_DEDUPLICATOR_H_

#include <atomic>

#include "base/base_export.h"
#include "base/task/sequence_manager/associated_thread_id.h"

namespace base {
namespace sequence_manager {
namespace internal {

// This class's job is to prevent redundant DoWorks being posted, which are
// expensive. The idea is a DoWork will (maybe) run a task before computing the
// delay till the next task. If the task run posts another task, we don't want
// it to schedule work because the DoWork will post a continuation as needed
// with the latest state taken into consideration (fences, enable / disable
// queue, task cancellation, etc...) Other threads can also post DoWork at any
// time, including while we're computing the delay till the next task. To
// account for that, we have split a DoWork up into two sections:
// [OnWorkStarted .. WillCheckForMoreWork] and
// [WillCheckForMoreWork .. DidCheckForMoreWork] where DidCheckForMoreWork
// detects if another thread called OnWorkRequested.
//
// Nesting is assumed to be dealt with by the ThreadController.
//
// Most methods are thread-affine except for On(Delayed)WorkRequested which are
// is thread-safe.
class BASE_EXPORT WorkDeduplicator { … };

}  // namespace internal
}  // namespace sequence_manager
}  // namespace base

#endif  // BASE_TASK_SEQUENCE_MANAGER_WORK_DEDUPLICATOR_H_