base/task_scheduler/task_scheduler_impl.h

// 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.

#ifndef BASE_TASK_SCHEDULER_TASK_SCHEDULER_IMPL_H_
#define BASE_TASK_SCHEDULER_TASK_SCHEDULER_IMPL_H_

#include <memory>
#include <vector>

#include "base/base_export.h"
#include "base/callback.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/atomic_flag.h"
#include "base/task_scheduler/scheduler_worker_pool_impl.h"
#include "base/task_scheduler/sequence.h"
#include "base/task_scheduler/task_scheduler.h"
#include "base/task_scheduler/task_tracker.h"
#include "base/task_scheduler/task_traits.h"
#include "base/threading/thread.h"
#include "build/build_config.h"

#if defined(OS_POSIX) && !defined(OS_NACL_SFI)
#include "base/task_scheduler/task_tracker_posix.h"
#endif

namespace base {

class HistogramBase;

namespace internal {

class DelayedTaskManager;
class SchedulerSingleThreadTaskRunnerManager;

// Default TaskScheduler implementation. This class is thread-safe.
class BASE_EXPORT TaskSchedulerImpl : public TaskScheduler {
 public:
  // Creates and returns an initialized TaskSchedulerImpl. CHECKs on failure.
  // |name| is used to label threads and histograms. It should identify the
  // component that creates the TaskScheduler. |init_params| contains params to
  // initialize worker pools.
  //
  // Note: The names and priority hints in |init_params| are ignored.
  // https://crbug.com/690706
  static std::unique_ptr<TaskSchedulerImpl> Create(
      const std::string& name,
      const TaskScheduler::InitParams& init_params);

  ~TaskSchedulerImpl() override;

  // TaskScheduler:
  void PostDelayedTaskWithTraits(const tracked_objects::Location& from_here,
                                 const TaskTraits& traits,
                                 OnceClosure task,
                                 TimeDelta delay) override;
  scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
      const TaskTraits& traits) override;
  scoped_refptr<SequencedTaskRunner> CreateSequencedTaskRunnerWithTraits(
      const TaskTraits& traits) override;
  scoped_refptr<SingleThreadTaskRunner> CreateSingleThreadTaskRunnerWithTraits(
      const TaskTraits& traits) override;
#if defined(OS_WIN)
  scoped_refptr<SingleThreadTaskRunner> CreateCOMSTATaskRunnerWithTraits(
      const TaskTraits& traits) override;
#endif  // defined(OS_WIN)
  std::vector<const HistogramBase*> GetHistograms() const override;
  int GetMaxConcurrentTasksWithTraitsDeprecated(
      const TaskTraits& traits) const override;
  void Shutdown() override;
  void FlushForTesting() override;
  void JoinForTesting() override;

 private:
  explicit TaskSchedulerImpl(const std::string& name);

  void Initialize(const TaskScheduler::InitParams& init_params);

  // Returns the worker pool that runs Tasks with |traits|.
  SchedulerWorkerPoolImpl* GetWorkerPoolForTraits(
      const TaskTraits& traits) const;

  // Callback invoked when a non-single-thread |sequence| isn't empty after a
  // worker pops a Task from it.
  void ReEnqueueSequenceCallback(scoped_refptr<Sequence> sequence);

  const std::string name_;
  Thread service_thread_;
#if defined(OS_POSIX) && !defined(OS_NACL_SFI)
  TaskTrackerPosix task_tracker_;
#else
  TaskTracker task_tracker_;
#endif
  std::unique_ptr<DelayedTaskManager> delayed_task_manager_;
  std::unique_ptr<SchedulerSingleThreadTaskRunnerManager>
      single_thread_task_runner_manager_;

  // There are 4 SchedulerWorkerPoolImpl in this array to match the 4
  // SchedulerWorkerPoolParams in TaskScheduler::InitParams.
  std::unique_ptr<SchedulerWorkerPoolImpl> worker_pools_[4];

#if DCHECK_IS_ON()
  // Set once JoinForTesting() has returned.
  AtomicFlag join_for_testing_returned_;
#endif

  DISALLOW_COPY_AND_ASSIGN(TaskSchedulerImpl);
};

}  // namespace internal
}  // namespace base

#endif  // BASE_TASK_SCHEDULER_TASK_SCHEDULER_IMPL_H_