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| 1 // Copyright 2017 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef MEDIA_MIDI_TASK_SERVICE_H_ |
| 6 #define MEDIA_MIDI_TASK_SERVICE_H_ |
| 7 |
| 8 #include "base/callback_forward.h" |
| 9 #include "base/macros.h" |
| 10 #include "base/memory/ref_counted.h" |
| 11 #include "base/single_thread_task_runner.h" |
| 12 #include "base/synchronization/lock.h" |
| 13 #include "base/threading/thread.h" |
| 14 #include "base/time/time.h" |
| 15 #include "media/midi/midi_export.h" |
| 16 |
| 17 namespace midi { |
| 18 |
| 19 // TaskService manages TaskRunners that can be used in midi and provides |
| 20 // functionalities to ensure thread safety. |
| 21 class MIDI_EXPORT TaskService final { |
| 22 public: |
| 23 using RunnerId = size_t; |
| 24 using InstanceId = int; |
| 25 |
| 26 static constexpr RunnerId kDefaultRunnerId = 0; |
| 27 |
| 28 TaskService(); |
| 29 ~TaskService(); |
| 30 |
| 31 // Issues an InstanceId internally to post tasks via PostBoundTask() and |
| 32 // PostDelayedBoundTask() with the InstanceId. Once UnbindInstance() is |
| 33 // called, tasks posted via these methods with unbind InstanceId won't be |
| 34 // invoked any more. |
| 35 // Returns true if call is bound or unbound correctly. Otherwise returns |
| 36 // false, that happens when the BindInstance() is called twice without |
| 37 // unbinding the previous instance. |
| 38 bool BindInstance(); |
| 39 bool UnbindInstance(); |
| 40 |
| 41 // Posts a task to run on a specified TaskRunner. |runner_id| should be |
| 42 // kDefaultRunnerId or a positive number. If kDefaultRunnerId is specified |
| 43 // the task runs on the thread on which BindInstance() is called. Other number |
| 44 // will run the task on a dedicated thread that is bound to the |runner_id|. |
| 45 void PostStaticTask(RunnerId runner_id, base::OnceClosure task); |
| 46 |
| 47 // Posts a task to run on a specified TaskRunner, and ensures that the bound |
| 48 // instance should not quit UnbindInstance() while a bound task is running. |
| 49 // See PostStaticTask() for |runner_id|. |
| 50 void PostBoundTask(RunnerId runner, base::OnceClosure task); |
| 51 void PostBoundDelayedTask(RunnerId runner_id, |
| 52 base::OnceClosure task, |
| 53 base::TimeDelta delay); |
| 54 |
| 55 private: |
| 56 // Returns a SingleThreadTaskRunner reference. Each TaskRunner will be |
| 57 // constructed on demand. |
| 58 scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner(RunnerId runner_id); |
| 59 |
| 60 // Helps to run a posted bound task on TaskRunner safely. |
| 61 void RunTask(InstanceId instance_id, |
| 62 RunnerId runner_id, |
| 63 base::OnceClosure task); |
| 64 |
| 65 // Keeps a TaskRunner for the thread that calls BindInstance() as a default |
| 66 // task runner to run posted tasks. |
| 67 scoped_refptr<base::SingleThreadTaskRunner> default_task_runner_; |
| 68 |
| 69 // Holds threads to host SingleThreadTaskRunners. |
| 70 std::vector<std::unique_ptr<base::Thread>> threads_; |
| 71 |
| 72 // Holds lock objects to ensure that tasks run while the instance is bound. |
| 73 std::vector<std::unique_ptr<base::Lock>> thread_task_locks_; |
| 74 |
| 75 // Holds InstanceId for the next bound instance. |
| 76 InstanceId next_instance_id_; |
| 77 |
| 78 // Holds InstanceId for the current bound instance. |
| 79 InstanceId bound_instance_id_; |
| 80 |
| 81 // Protects |next_instance_id_| and |bound_instance_id_|. |
| 82 base::Lock instance_lock_; |
| 83 |
| 84 // Protects all other members. |
| 85 base::Lock lock_; |
| 86 |
| 87 // If multiple locks should be obtained simultaneously, we should acquire them |
| 88 // in the order below so to avoid deadklocks. |
| 89 // |instance_lock_| -> |lock_| -> |(one of) thread_task_locks_|. |
| 90 |
| 91 DISALLOW_COPY_AND_ASSIGN(TaskService); |
| 92 }; |
| 93 |
| 94 }; // namespace midi |
| 95 |
| 96 #endif // MEDIA_MIDI_TASK_SERVICE_H_ |
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