| // 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_SCHEDULER_WORKER_THREAD_H_ |
| #define BASE_TASK_SCHEDULER_SCHEDULER_WORKER_THREAD_H_ |
| |
| #include <memory> |
| |
| #include "base/base_export.h" |
| #include "base/macros.h" |
| #include "base/memory/ref_counted.h" |
| #include "base/synchronization/waitable_event.h" |
| #include "base/task_scheduler/scheduler_lock.h" |
| #include "base/task_scheduler/sequence.h" |
| #include "base/threading/platform_thread.h" |
| |
| namespace base { |
| namespace internal { |
| |
| class TaskTracker; |
| |
| // A thread that runs Tasks from Sequences returned by a delegate. |
| // |
| // A SchedulerWorkerThread starts out sleeping. It is woken up by a call to |
| // WakeUp(). After a wake-up, a SchedulerWorkerThread runs Tasks from Sequences |
| // returned by the GetWork() method of its delegate as long as it doesn't return |
| // nullptr. It also periodically checks with its TaskTracker whether shutdown |
| // has completed and exits when it has. |
| // |
| // This class is thread-safe. |
| class BASE_EXPORT SchedulerWorkerThread : public PlatformThread::Delegate { |
| public: |
| // Delegate interface for SchedulerWorkerThread. The methods are always called |
| // from the thread managed by the SchedulerWorkerThread instance. |
| class Delegate { |
| public: |
| virtual ~Delegate() = default; |
| |
| // Called by |worker_thread| when it enters its main function. |
| virtual void OnMainEntry(SchedulerWorkerThread* worker_thread) = 0; |
| |
| // Called by |worker_thread| to get a Sequence from which to run a Task. |
| virtual scoped_refptr<Sequence> GetWork( |
| SchedulerWorkerThread* worker_thread) = 0; |
| |
| // Called when |sequence| isn't empty after the SchedulerWorkerThread pops a |
| // Task from it. |sequence| is the last Sequence returned by GetWork(). |
| virtual void ReEnqueueSequence(scoped_refptr<Sequence> sequence) = 0; |
| }; |
| |
| // Creates a SchedulerWorkerThread with priority |thread_priority| that runs |
| // Tasks from Sequences returned by |delegate|. |task_tracker| is used to |
| // handle shutdown behavior of Tasks. Returns nullptr if creating the |
| // underlying platform thread fails. |
| static std::unique_ptr<SchedulerWorkerThread> Create( |
| ThreadPriority thread_priority, |
| std::unique_ptr<Delegate> delegate, |
| TaskTracker* task_tracker); |
| |
| // Destroying a SchedulerWorkerThread in production is not allowed; it is |
| // always leaked. In tests, it can only be destroyed after JoinForTesting() |
| // has returned. |
| ~SchedulerWorkerThread() override; |
| |
| // Wakes up this SchedulerWorkerThread if it wasn't already awake. After this |
| // is called, this SchedulerWorkerThread will run Tasks from Sequences |
| // returned by the GetWork() method of its delegate until it returns nullptr. |
| void WakeUp(); |
| |
| SchedulerWorkerThread::Delegate* delegate() { return delegate_.get(); } |
| |
| // Joins this SchedulerWorkerThread. If a Task is already running, it will be |
| // allowed to complete its execution. This can only be called once. |
| void JoinForTesting(); |
| |
| private: |
| SchedulerWorkerThread(ThreadPriority thread_priority, |
| std::unique_ptr<Delegate> delegate, |
| TaskTracker* task_tracker); |
| |
| // PlatformThread::Delegate: |
| void ThreadMain() override; |
| |
| bool ShouldExitForTesting() const; |
| |
| // Platform thread managed by this SchedulerWorkerThread. |
| PlatformThreadHandle thread_handle_; |
| |
| // Event signaled to wake up this SchedulerWorkerThread. |
| WaitableEvent wake_up_event_; |
| |
| const std::unique_ptr<Delegate> delegate_; |
| TaskTracker* const task_tracker_; |
| |
| // Synchronizes access to |should_exit_for_testing_|. |
| mutable SchedulerLock should_exit_for_testing_lock_; |
| |
| // True once JoinForTesting() has been called. |
| bool should_exit_for_testing_ = false; |
| |
| DISALLOW_COPY_AND_ASSIGN(SchedulerWorkerThread); |
| }; |
| |
| } // namespace internal |
| } // namespace base |
| |
| #endif // BASE_TASK_SCHEDULER_SCHEDULER_WORKER_THREAD_H_ |