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Side by Side Diff: base/task_scheduler/scheduler_thread_pool.h

Issue 1708773002: TaskScheduler [7] SchedulerThreadPool (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@s_5_worker_thread
Patch Set: Wake up a thread explicitly when a Sequence is added in a PQ. Created 4 years, 8 months ago
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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_SCHEDULER_THREAD_POOL_H_
6 #define BASE_TASK_SCHEDULER_SCHEDULER_THREAD_POOL_H_
7
8 #include <stddef.h>
9
10 #include <memory>
11 #include <stack>
12 #include <vector>
13
14 #include "base/base_export.h"
15 #include "base/callback.h"
16 #include "base/macros.h"
17 #include "base/memory/ref_counted.h"
18 #include "base/synchronization/condition_variable.h"
19 #include "base/task_runner.h"
20 #include "base/task_scheduler/priority_queue.h"
21 #include "base/task_scheduler/scheduler_lock.h"
22 #include "base/task_scheduler/scheduler_task_executor.h"
23 #include "base/task_scheduler/scheduler_worker_thread.h"
24 #include "base/task_scheduler/sequence.h"
25 #include "base/task_scheduler/task.h"
26 #include "base/task_scheduler/task_traits.h"
27 #include "base/threading/platform_thread.h"
28
29 namespace base {
30 namespace internal {
31
32 struct SequenceSortKey;
33 class TaskTracker;
34
35 // A pool of threads that run Tasks. This class is thread-safe.
36 class BASE_EXPORT SchedulerThreadPool : public SchedulerTaskExecutor {
37 public:
38 // Callback invoked when a Sequence isn't empty after a worker thread pops a
39 // Task from it.
40 using EnqueueSequenceCallback = Callback<void(scoped_refptr<Sequence>)>;
41
42 // Creates a SchedulerThreadPool with up to |max_threads| threads of priority
43 // |thread_priority|. |enqueue_sequence_callback| will be invoked after a
44 // thread of this thread pool tries to run a Task. |task_tracker| is used to
45 // handle shutdown behavior of Tasks. Returns nullptr on failure to create a
46 // thread pool with at least one thread.
47 static std::unique_ptr<SchedulerThreadPool> CreateThreadPool(
48 ThreadPriority thread_priority,
49 size_t max_threads,
50 const EnqueueSequenceCallback& enqueue_sequence_callback,
51 TaskTracker* task_tracker);
52
53 // Destroying a SchedulerThreadPool returned by CreateThreadPool() is not
54 // allowed in production; it is always leaked. In tests, it can only be
55 // destroyed after JoinForTesting() has returned.
56 ~SchedulerThreadPool() override;
robliao 2016/04/13 20:50:55 Nit: This should go above the static function abov
fdoray 2016/04/13 23:13:12 Done.
57
58 // Returns a TaskRunner whose PostTask invocations will result in scheduling
59 // Tasks with |traits| and |execution_mode| in this thread pool.
60 scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
61 const TaskTraits& traits,
62 ExecutionMode execution_mode);
63
64 // Inserts |sequence| into this thread pool's shared priority queue with
65 // |sequence_sort_key|. Must only be called from a worker thread to put
66 // |sequence| back into a PriorityQueue after running a Task from it. The
67 // worker thread doesn't have to belong to this thread pool.
68 void EnqueueSequence(scoped_refptr<Sequence> sequence,
69 const SequenceSortKey& sequence_sort_key);
70
71 // Waits until all threads are idle.
72 void WaitForAllWorkerThreadsIdleForTesting();
73
74 // Joins all threads of this thread pool. Tasks that are already running are
75 // allowed to complete their execution. This can only be called once.
76 void JoinForTesting();
77
78 private:
79 class SchedulerWorkerThreadDelegateImpl;
80
81 SchedulerThreadPool(const EnqueueSequenceCallback& enqueue_sequence_callback,
82 TaskTracker* task_tracker);
83
84 bool Initialize(ThreadPriority thread_priority, size_t max_threads);
85
86 // Wakes up the last thread from this thread pool to go idle, if any.
87 void WakeUpOneThread();
88
89 // Adds |worker_thread| to |idle_worker_threads_stack_|.
90 void AddToIdleWorkerThreadsStack(SchedulerWorkerThread* worker_thread);
91
92 // SchedulerTaskExecutor:
93 void PostTaskNow(std::unique_ptr<Task> task,
94 scoped_refptr<Sequence> sequence) override;
95
96 // PriorityQueue from which all threads of this thread pool get work.
97 PriorityQueue shared_priority_queue_;
98
99 // All worker threads owned by this thread pool. Is only modified during
robliao 2016/04/13 20:50:55 Nit: "It is only modified" or "Only modified"
fdoray 2016/04/13 23:13:12 Done.
100 // initialization of the thread pool.
101 std::vector<std::unique_ptr<SchedulerWorkerThread>> worker_threads_;
102
103 // Synchronizes access to |idle_worker_threads_stack_| and
104 // |idle_worker_threads_stack_cv_for_testing_|. Has |shared_priority_queue_|'s
105 // lock as its predecessor so that a thread can be pushed to
106 // |idle_worker_threads_stack_| within the scope of a Transaction (more
107 // details in GetWork()).
108 SchedulerLock idle_worker_threads_stack_lock_;
109
110 // Stack of idle worker threads.
111 std::stack<SchedulerWorkerThread*> idle_worker_threads_stack_;
112
113 // Signaled when all worker threads become idle.
114 std::unique_ptr<ConditionVariable> idle_worker_threads_stack_cv_for_testing_;
115
116 // Signaled once JoinForTesting() has returned.
117 WaitableEvent join_for_testing_returned_;
118
119 // Delegate for all worker threads in this pool.
120 std::unique_ptr<SchedulerWorkerThread::Delegate> worker_thread_delegate_;
121
122 TaskTracker* const task_tracker_;
123
124 DISALLOW_COPY_AND_ASSIGN(SchedulerThreadPool);
125 };
126
127 } // namespace internal
128 } // namespace base
129
130 #endif // BASE_TASK_SCHEDULER_SCHEDULER_THREAD_POOL_H_
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