| // 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_H_ |
| #define BASE_TASK_SCHEDULER_TASK_SCHEDULER_H_ |
| |
| #include <memory> |
| #include <vector> |
| |
| #include "base/base_export.h" |
| #include "base/callback_forward.h" |
| #include "base/memory/ref_counted.h" |
| #include "base/sequenced_task_runner.h" |
| #include "base/single_thread_task_runner.h" |
| #include "base/task_runner.h" |
| #include "base/task_scheduler/task_traits.h" |
| |
| namespace tracked_objects { |
| class Location; |
| } |
| |
| namespace base { |
| |
| class HistogramBase; |
| class SchedulerWorkerPoolParams; |
| |
| // Interface for a task scheduler and static methods to manage the instance used |
| // by the post_task.h API. Note: all base/task_scheduler users should go through |
| // post_task.h instead of TaskScheduler except for the one callsite per process |
| // which manages the process' instance. |
| class BASE_EXPORT TaskScheduler { |
| public: |
| // 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)>; |
| |
| virtual ~TaskScheduler() = default; |
| |
| // Posts |task| with specific |traits|. |
| // For one off tasks that don't require a TaskRunner. |
| virtual void PostTaskWithTraits(const tracked_objects::Location& from_here, |
| const TaskTraits& traits, |
| const Closure& task) = 0; |
| |
| // Returns a TaskRunner whose PostTask invocations result in scheduling tasks |
| // using |traits|. Tasks may run in any order and in parallel. |
| virtual scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits( |
| const TaskTraits& traits) = 0; |
| |
| // Returns a SequencedTaskRunner whose PostTask invocations result in |
| // scheduling tasks using |traits|. Tasks run one at a time in posting order. |
| virtual scoped_refptr<SequencedTaskRunner> |
| CreateSequencedTaskRunnerWithTraits(const TaskTraits& traits) = 0; |
| |
| // Returns a SingleThreadTaskRunner whose PostTask invocations result in |
| // scheduling tasks using |traits|. Tasks run on a single thread in posting |
| // order. |
| virtual scoped_refptr<SingleThreadTaskRunner> |
| CreateSingleThreadTaskRunnerWithTraits(const TaskTraits& traits) = 0; |
| |
| // Returns a vector of all histograms available in this task scheduler. |
| virtual std::vector<const HistogramBase*> GetHistograms() const = 0; |
| |
| // Synchronously shuts down the scheduler. Once this is called, only tasks |
| // posted with the BLOCK_SHUTDOWN behavior will be run. When this returns: |
| // - All SKIP_ON_SHUTDOWN tasks that were already running have completed their |
| // execution. |
| // - All posted BLOCK_SHUTDOWN tasks have completed their execution. |
| // - CONTINUE_ON_SHUTDOWN tasks might still be running. |
| // Note that an implementation can keep threads and other resources alive to |
| // support running CONTINUE_ON_SHUTDOWN after this returns. This can only be |
| // called once. |
| virtual void Shutdown() = 0; |
| |
| // Waits until there are no pending undelayed tasks. May be called in tests |
| // to validate that a condition is met after all undelayed tasks have run. |
| // |
| // Does not wait for delayed tasks. Waits for undelayed tasks posted from |
| // other threads during the call. Returns immediately when shutdown completes. |
| virtual void FlushForTesting() = 0; |
| |
| // CreateAndSetDefaultTaskScheduler() and SetInstance() register a |
| // TaskScheduler to handle tasks posted through the post_task.h API for this |
| // process. The registered TaskScheduler will only be deleted when a new |
| // TaskScheduler is registered and is leaked on shutdown. The methods must |
| // not be called when TaskRunners created by the previous TaskScheduler are |
| // still alive. The methods are not thread-safe; proper synchronization is |
| // required to use the post_task.h API after registering a new TaskScheduler. |
| |
| // Creates and sets a default task scheduler. CHECKs on failure. |
| // |worker_pool_params_vector| 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 void CreateAndSetDefaultTaskScheduler( |
| const std::vector<SchedulerWorkerPoolParams>& worker_pool_params_vector, |
| const WorkerPoolIndexForTraitsCallback& |
| worker_pool_index_for_traits_callback); |
| |
| // Registers |task_scheduler| to handle tasks posted through the post_task.h |
| // API for this process. |
| static void SetInstance(std::unique_ptr<TaskScheduler> task_scheduler); |
| |
| // Retrieve the TaskScheduler set via CreateAndSetDefaultTaskScheduler() or |
| // SetInstance(). This should be used very rarely; most users of TaskScheduler |
| // should use the post_task.h API. |
| static TaskScheduler* GetInstance(); |
| }; |
| |
| } // namespace base |
| |
| #endif // BASE_TASK_SCHEDULER_TASK_SCHEDULER_H_ |