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1 // Copyright 2016 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 BASE_TASK_SCHEDULER_THREAD_POOL_H_ | |
6 #define BASE_TASK_SCHEDULER_THREAD_POOL_H_ | |
7 | |
8 #include <stddef.h> | |
9 | |
10 #include <stack> | |
11 #include <vector> | |
12 | |
13 #include "base/base_export.h" | |
14 #include "base/macros.h" | |
15 #include "base/memory/ref_counted.h" | |
16 #include "base/memory/scoped_ptr.h" | |
17 #include "base/synchronization/condition_variable.h" | |
18 #include "base/task_runner.h" | |
19 #include "base/task_scheduler/priority_queue.h" | |
20 #include "base/task_scheduler/scheduler_lock.h" | |
21 #include "base/task_scheduler/scheduler_worker_thread.h" | |
22 #include "base/task_scheduler/sequence.h" | |
23 #include "base/task_scheduler/task_traits.h" | |
24 #include "base/threading/platform_thread.h" | |
25 #include "base/threading/thread_local.h" | |
26 | |
27 namespace base { | |
28 namespace internal { | |
29 | |
30 struct SequenceSortKey; | |
31 class TaskTracker; | |
32 | |
33 // A pool of threads that run Tasks. This class is thread-safe. | |
34 class BASE_EXPORT ThreadPool { | |
35 public: | |
36 // Creates a ThreadPool with |num_threads| threads of priority | |
37 // |thread_priority|. |ran_task_from_sequence_callback| is invoked after a | |
38 // thread of this ThreadPool tries to run a Task from a Sequence. | |
39 // |task_tracker| is used to handle shutdown behavior of Tasks. Returns | |
40 // nullptr if when it fails to create a ThreadPool with at least one thread. | |
41 static scoped_ptr<ThreadPool> CreateThreadPool( | |
42 ThreadPriority thread_priority, | |
43 size_t num_threads, | |
44 const SchedulerWorkerThread::RanTaskFromSequenceCallback& | |
45 ran_task_from_sequence_callback, | |
46 TaskTracker* task_tracker); | |
47 | |
48 // Destroying a ThreadPool in production is not allowed; it is always leaked. | |
49 // In tests, it can only be destroyed after JoinForTesting() has returned. | |
50 ~ThreadPool(); | |
51 | |
52 // Returns a TaskRunner whose PostTask invocations will result in scheduling | |
53 // Tasks with |traits| and |execution_mode| in this ThreadPool. | |
54 scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits( | |
55 const TaskTraits& traits, | |
56 ExecutionMode execution_mode); | |
57 | |
58 // Reinserts |sequence| in |shared_priority_queue_| with |sequence_sort_key| | |
59 // after |worker_thread| has run a Task from it. Note that |worker_thread| | |
robliao
2016/03/31 22:48:56
The second part of this is an implementation detai
fdoray
2016/04/01 16:02:52
Done.
robliao
2016/04/01 19:14:49
Looking at the code side-by-side, do we need worke
fdoray
2016/04/01 20:16:45
Removed it.
| |
60 // doesn't necessarily belong to this ThreadPool. | |
61 void ReinsertSequence(const SchedulerWorkerThread* worker_thread, | |
62 scoped_refptr<Sequence> sequence, | |
63 const SequenceSortKey& sequence_sort_key); | |
64 | |
65 // Waits until all threads are idle. | |
66 void WaitForAllWorkerThreadsIdleForTesting(); | |
67 | |
68 // Joins all threads of this ThreadPool. Tasks that are already running are | |
69 // allowed to complete their execution. This can only be called once. | |
70 void JoinForTesting(); | |
71 | |
72 private: | |
73 ThreadPool(ThreadPriority thread_priority, | |
74 size_t num_threads, | |
75 const SchedulerWorkerThread::RanTaskFromSequenceCallback& | |
76 ran_task_from_sequence_callback, | |
77 TaskTracker* task_tracker); | |
78 | |
79 // Wakes up one thread from this ThreadPool if they aren't all busy. | |
80 void WakeUpOneThread(); | |
81 | |
82 // Adds |worker_thread| to |idle_worker_threads_stack_|. | |
83 void AddToIdleSchedulerWorkerThreadsStack( | |
84 SchedulerWorkerThread* worker_thread); | |
85 | |
86 // Invoked when a sequence is inserted in |shared_priority_queue_|. | |
87 void SequenceInsertedInSharedPriorityQueueCallback(); | |
88 | |
89 // Invoked when the main function of a worker thread is entered. | |
90 void MainEntryCallback() const; | |
91 | |
92 // Invoked by a worker thread to get a Sequence from which to run a Task. | |
93 scoped_refptr<Sequence> GetWorkCallback(SchedulerWorkerThread* worker_thread); | |
94 | |
95 // PriorityQueue from which all threads of this ThreadPool get work. | |
96 PriorityQueue shared_priority_queue_; | |
97 | |
98 // All worker threads owned by this ThreadPool. This is only modified by the | |
99 // constructor. | |
100 std::vector<scoped_ptr<SchedulerWorkerThread>> worker_threads_; | |
101 | |
102 // True if WakeUpOneThread() shouldn't be called when a Sequence is inserted | |
103 // in |shared_priority_queue_| by a given thread. | |
104 ThreadLocalBoolean no_wake_up_on_sequence_insertion_; | |
105 | |
106 // Synchronizes access to |idle_worker_threads_stack_| and | |
107 // |idle_worker_threads_cv_|. | |
108 SchedulerLock idle_worker_threads_stack_lock_; | |
109 | |
110 // Stack of idle worker threads. The last worker thread that became idle is on | |
111 // top of the stack. | |
112 std::stack<SchedulerWorkerThread*> idle_worker_threads_stack_; | |
113 | |
114 // Signaled when all worker threads become idle. | |
115 scoped_ptr<ConditionVariable> idle_worker_threads_stack_cv_; | |
116 | |
117 // Synchronizes access to |join_for_testing_returned_|. | |
118 SchedulerLock join_for_testing_returned_lock_; | |
119 | |
120 // True once JoinForTesting() has returned. | |
121 bool join_for_testing_returned_ = false; | |
122 | |
123 TaskTracker* const task_tracker_; | |
124 | |
125 DISALLOW_COPY_AND_ASSIGN(ThreadPool); | |
126 }; | |
127 | |
128 } // namespace internal | |
129 } // namespace base | |
130 | |
131 #endif // BASE_TASK_SCHEDULER_THREAD_POOL_H_ | |
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