Index: base/task_scheduler/worker_thread.h |
diff --git a/base/task_scheduler/worker_thread.h b/base/task_scheduler/worker_thread.h |
new file mode 100644 |
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+++ b/base/task_scheduler/worker_thread.h |
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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_WORKER_THREAD_H_ |
+#define BASE_TASK_SCHEDULER_WORKER_THREAD_H_ |
+ |
+#include <iosfwd> |
+ |
+#include "base/atomicops.h" |
+#include "base/base_export.h" |
+#include "base/callback.h" |
+#include "base/macros.h" |
+#include "base/memory/ref_counted.h" |
+#include "base/memory/scoped_ptr.h" |
+#include "base/single_thread_task_runner.h" |
+#include "base/synchronization/waitable_event.h" |
+#include "base/task_scheduler/priority_queue.h" |
+#include "base/task_scheduler/sequence.h" |
+#include "base/task_scheduler/task_traits.h" |
+#include "base/threading/platform_thread.h" |
+ |
+namespace base { |
+namespace internal { |
+ |
+class TaskTracker; |
+ |
+// A thread that runs Tasks from a shared and a single-threaded PriorityQueue. |
+// |
+// There is no guarantee that a WorkerThread will run work from its shared |
+// PriorityQueue unless WakeUp() is called after the work is added. This allows |
+// a ThreadPool to choose which WorkerThread should run the new work. On the |
+// other hand, a WorkerThread is woken up automatically when Tasks are added to |
+// its single-threaded PriorityQueue. |
+// |
+// This class is thread-safe. |
+class BASE_EXPORT WorkerThread : public PlatformThread::Delegate { |
+ public: |
+ // Possible states for a WorkerThread. |
+ enum class State { |
+ BUSY, |
+ IDLE, |
+ }; |
+ |
+ // Callback invoked to indicate that a shared |sequence| is not empty after |
+ // |worker_thread| has popped a Task from it. |
+ using SharedSequenceStillHasTasksCallback = |
+ Callback<void(const WorkerThread* worker_thread, |
+ scoped_refptr<Sequence> sequence)>; |
+ |
+ // Callback invoked when the state of |worker_thread| becomes |state|. |
+ using StateChangedCallback = |
+ Callback<void(WorkerThread* worker_thread, State state)>; |
+ |
+ // Creates a WorkerThread with priority |thread_priority| that runs Tasks from |
+ // its single-threaded PriorityQueue and from |shared_priority_queue|. |
robliao
2016/03/24 23:03:26
Nit: |single_thread_priority_queue_| and from |sha
fdoray
2016/03/29 18:33:34
The intent of this comment is to describe the argu
|
+ // |shared_sequence_still_has_tasks_callback| is invoked when a Sequence |
+ // extracted from |shared_priority_queue| isn't empty after the WorkerThread |
+ // has popped a task from it. |state_changed_callback| is invoked when the |
+ // WorkerThread becomes IDLE or BUSY. |task_tracker| is used to handle |
+ // shutdown behavior of Tasks. |
+ static scoped_ptr<WorkerThread> CreateWorkerThread( |
+ ThreadPriority thread_priority, |
+ PriorityQueue* shared_priority_queue, |
+ const SharedSequenceStillHasTasksCallback& |
+ shared_sequence_still_has_tasks_callback, |
+ const StateChangedCallback& state_changed_callback, |
+ TaskTracker* task_tracker); |
+ |
+ // Destroying a WorkerThread in production is not allowed. In tests, it can |
robliao
2016/03/24 23:03:26
How are we planning on reclaiming WorkerThreads in
fdoray
2016/03/29 18:33:34
Once a WorkerThread has been created in production
robliao
2016/03/30 00:42:42
I think this will be hard to determine until we ac
|
+ // only be destroyed after JoinForTesting() has returned. |
+ ~WorkerThread() override; |
+ |
+ // Wakes up this WorkerThread. When this is called, this WorkerThread will run |
+ // until both its PriorityQueues become empty. |
+ void WakeUp(); |
+ |
+ // Returns a SingleThreadTaskRunner whose PostTask invocations will result in |
+ // scheduling Tasks with |traits| on this WorkerThread. |
+ scoped_refptr<SingleThreadTaskRunner> CreateTaskRunnerWithTraits( |
+ const TaskTraits& traits); |
+ |
+ // Joins this WorkerThread. If a Task is already running, it will be allowed |
+ // to complete its execution. This can only be called once. |
+ void JoinForTesting(); |
+ |
+ private: |
+ WorkerThread(ThreadPriority thread_priority, |
+ PriorityQueue* shared_priority_queue, |
+ const SharedSequenceStillHasTasksCallback& |
+ shared_sequence_still_has_tasks_callback, |
+ const StateChangedCallback& state_changed_callback, |
+ TaskTracker* task_tracker); |
+ |
+ // Extracts the Sequence with the highest priority from |
+ // |shared_priority_queue_| or |single_thread_priority_queue_|. |
+ // |is_single_threaded| is set to true if the returned Sequence comes from |
+ // |single_thread_priority_queue_|. |
+ scoped_refptr<Sequence> GetWork(bool* is_single_threaded); |
+ |
+ // Sets the state of this WorkerThread. |
+ void SetState(State state); |
+ |
+ // PlatformThread::Delegate: |
+ void ThreadMain() override; |
+ |
+ bool should_exit_for_testing() const { |
+ base::subtle::MemoryBarrier(); |
+ return should_exit_for_testing_; |
+ } |
+ |
+ // Platform thread managed by this WorkerThread. |
+ PlatformThreadHandle thread_handle_; |
+ |
+ // Current state of this WorkerThread. |
+ State state_ = State::BUSY; |
+ |
+ // Event signaled to wake up this WorkerThread. |
+ WaitableEvent wake_up_event_; |
+ |
+ // The single-threaded PriorityQueue from which this WorkerThread gets work. |
+ PriorityQueue single_thread_priority_queue_; |
+ |
+ // The shared PriorityQueue from which this WorkerThread gets work. |
+ PriorityQueue* const shared_priority_queue_; |
+ |
+ const SharedSequenceStillHasTasksCallback |
+ shared_sequence_still_has_tasks_callback_; |
+ const StateChangedCallback state_changed_callback_; |
+ TaskTracker* const task_tracker_; |
+ |
+ // True once JoinForTesting() has been called. |
+ bool should_exit_for_testing_ = false; |
+ |
+ DISALLOW_COPY_AND_ASSIGN(WorkerThread); |
+}; |
+ |
+BASE_EXPORT std::ostream& operator<<(std::ostream& os, |
+ WorkerThread::State state); |
+ |
+} // namespace internal |
+} // namespace base |
+ |
+#endif // BASE_TASK_SCHEDULER_WORKER_THREAD_H_ |