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// 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 <stddef.h>
#include <memory>
#include <string>
#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/waitable_event.h"
#include "base/task_runner.h"
#include "base/task_scheduler/delayed_task_manager.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"
namespace base {
namespace internal {
class SchedulerServiceThread;
// Default TaskScheduler implementation. This class is thread-safe.
class BASE_EXPORT TaskSchedulerImpl : public TaskScheduler {
public:
struct WorkerPoolCreationArgs {
// Name of the pool. Used to label the pool's threads.
std::string name;
// Priority of the pool's threads.
ThreadPriority thread_priority;
// Whether I/O is allowed in the pool.
SchedulerWorkerPoolImpl::IORestriction io_restriction;
// Maximum number of threads in the pool.
size_t max_threads;
};
// Returns the index of the worker pool in which a task with |traits| should
// run. This should be coded in a future-proof way: new traits should
// gracefully map to a default pool.
using WorkerPoolIndexForTraitsCallback =
Callback<size_t(const TaskTraits& traits)>;
// Creates and returns an initialized TaskSchedulerImpl. CHECKs on failure.
// |worker_pools| describes the worker pools to create.
// |worker_pool_index_for_traits_callback| returns the index in |worker_pools|
// of the worker pool in which a task with given traits should run.
static std::unique_ptr<TaskSchedulerImpl> Create(
const std::vector<WorkerPoolCreationArgs>& worker_pools,
const WorkerPoolIndexForTraitsCallback&
worker_pool_index_for_traits_callback);
// Destroying a TaskSchedulerImpl is not allowed in production; it is always
// leaked. In tests, it can only be destroyed after JoinForTesting() has
// returned.
~TaskSchedulerImpl() override;
// TaskScheduler:
void PostTaskWithTraits(const tracked_objects::Location& from_here,
const TaskTraits& traits,
const Closure& task) override;
scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
const TaskTraits& traits,
ExecutionMode execution_mode) override;
void Shutdown() override;
// Joins all threads of this scheduler. Tasks that are already running are
// allowed to complete their execution. This can only be called once.
void JoinForTesting();
private:
TaskSchedulerImpl(const WorkerPoolIndexForTraitsCallback&
worker_pool_index_for_traits_callback);
void Initialize(const std::vector<WorkerPoolCreationArgs>& worker_pools);
// Returns the worker pool that runs Tasks with |traits|.
SchedulerWorkerPool* GetWorkerPoolForTraits(const TaskTraits& traits);
// 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);
// Callback invoked when the delayed run time is changed from the
// DelayedTaskManager.
void OnDelayedRunTimeUpdated();
TaskTracker task_tracker_;
DelayedTaskManager delayed_task_manager_;
const WorkerPoolIndexForTraitsCallback worker_pool_index_for_traits_callback_;
std::vector<std::unique_ptr<SchedulerWorkerPoolImpl>> worker_pools_;
std::unique_ptr<SchedulerServiceThread> service_thread_;
#if DCHECK_IS_ON()
// Signaled once JoinForTesting() has returned.
WaitableEvent join_for_testing_returned_;
#endif
DISALLOW_COPY_AND_ASSIGN(TaskSchedulerImpl);
};
} // namespace internal
} // namespace base
#endif // BASE_TASK_SCHEDULER_TASK_SCHEDULER_IMPL_H_
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