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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 #include "base/task_scheduler/worker_thread.h" | |
6 | |
7 #include <ostream> | |
8 #include <utility> | |
9 | |
10 #include "base/bind.h" | |
11 #include "base/logging.h" | |
12 #include "base/task_scheduler/task_tracker.h" | |
13 #include "base/task_scheduler/utils.h" | |
14 #include "base/time/time.h" | |
15 | |
16 namespace base { | |
17 namespace internal { | |
18 | |
19 namespace { | |
20 | |
21 class SchedulerSingleThreadTaskRunner : public SingleThreadTaskRunner { | |
22 public: | |
23 SchedulerSingleThreadTaskRunner(const TaskTraits& traits, | |
24 PriorityQueue* single_thread_priority_queue, | |
25 TaskTracker* task_tracker); | |
26 | |
27 // SingleThreadTaskRunner: | |
28 bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here, | |
29 const Closure& task, | |
30 TimeDelta delay) override; | |
31 bool PostDelayedTask(const tracked_objects::Location& from_here, | |
32 const Closure& closure, | |
33 TimeDelta delay) override; | |
34 bool RunsTasksOnCurrentThread() const override; | |
35 | |
36 private: | |
37 ~SchedulerSingleThreadTaskRunner() override; | |
38 | |
39 const TaskTraits traits_; | |
40 const scoped_refptr<Sequence> sequence_; | |
41 PriorityQueue* const priority_queue_; | |
42 TaskTracker* const task_tracker_; | |
43 | |
44 DISALLOW_COPY_AND_ASSIGN(SchedulerSingleThreadTaskRunner); | |
45 }; | |
46 | |
47 SchedulerSingleThreadTaskRunner::SchedulerSingleThreadTaskRunner( | |
48 const TaskTraits& traits, | |
49 PriorityQueue* single_thread_priority_queue, | |
50 TaskTracker* task_tracker) | |
51 : traits_(traits), | |
52 sequence_(new Sequence), | |
53 priority_queue_(single_thread_priority_queue), | |
54 task_tracker_(task_tracker) {} | |
55 | |
56 bool SchedulerSingleThreadTaskRunner::PostDelayedTask( | |
57 const tracked_objects::Location& from_here, | |
58 const Closure& closure, | |
59 TimeDelta delay) { | |
60 // TODO(fdoray): Support delayed tasks. | |
61 DCHECK(delay.is_zero()); | |
62 PostTaskHelper(make_scoped_ptr(new Task(from_here, closure, traits_)), | |
63 sequence_, priority_queue_, task_tracker_); | |
64 return true; | |
65 } | |
66 | |
67 bool SchedulerSingleThreadTaskRunner::RunsTasksOnCurrentThread() const { | |
68 // TODO(fdoray): Return true only if tasks posted may actually run on the | |
69 // current thread. It is valid, but not ideal, to always return true. | |
70 return true; | |
71 } | |
72 | |
73 bool SchedulerSingleThreadTaskRunner::PostNonNestableDelayedTask( | |
74 const tracked_objects::Location& from_here, | |
75 const Closure& task, | |
76 TimeDelta delay) { | |
77 // Tasks are never nested on WorkerThread. | |
78 return PostDelayedTask(from_here, task, delay); | |
79 } | |
80 | |
81 SchedulerSingleThreadTaskRunner::~SchedulerSingleThreadTaskRunner() = default; | |
82 | |
83 // Extracts the Sequence with the highest priority from |shared_transaction| or | |
84 // |single_thread_transaction|. |is_single_threaded| is set to true if the | |
85 // returned Sequence comes from |single_thread_transaction|. | |
86 scoped_refptr<Sequence> GetWork( | |
87 PriorityQueue::Transaction* shared_transaction, | |
88 PriorityQueue::Transaction* single_thread_transaction, | |
89 bool* is_single_threaded) { | |
90 DCHECK(shared_transaction); | |
91 DCHECK(single_thread_transaction); | |
92 DCHECK(is_single_threaded); | |
robliao
2016/03/30 00:42:42
Done as in DCHECK necessary or DCHECK unnecessary?
fdoray
2016/03/30 18:44:49
I removed it in patch set 11... and I re-added it
| |
93 | |
94 *is_single_threaded = false; | |
95 | |
96 const PriorityQueue::SequenceAndSortKey shared_sequence = | |
97 shared_transaction->Peek(); | |
98 const PriorityQueue::SequenceAndSortKey single_thread_sequence = | |
99 single_thread_transaction->Peek(); | |
100 | |
101 if (single_thread_sequence.is_null() && shared_sequence.is_null()) | |
102 return scoped_refptr<Sequence>(); | |
103 | |
104 if (single_thread_sequence.is_null() || | |
105 (!shared_sequence.is_null() && | |
106 single_thread_sequence.sort_key < shared_sequence.sort_key)) { | |
107 shared_transaction->Pop(); | |
108 return shared_sequence.sequence; | |
109 } | |
110 | |
111 DCHECK(!single_thread_sequence.is_null()); | |
112 single_thread_transaction->Pop(); | |
113 *is_single_threaded = true; | |
114 return single_thread_sequence.sequence; | |
115 } | |
116 | |
117 } // namespace | |
118 | |
119 scoped_ptr<WorkerThread> WorkerThread::CreateWorkerThread( | |
120 ThreadPriority thread_priority, | |
121 PriorityQueue* shared_priority_queue, | |
122 const SharedSequenceStillHasTasksCallback& | |
123 shared_sequence_still_has_tasks_callback, | |
124 const StateChangedCallback& state_changed_callback, | |
125 TaskTracker* task_tracker) { | |
126 scoped_ptr<WorkerThread> worker_thread( | |
127 new WorkerThread(thread_priority, shared_priority_queue, | |
128 shared_sequence_still_has_tasks_callback, | |
129 state_changed_callback, task_tracker)); | |
130 | |
131 if (worker_thread->thread_handle_.is_null()) | |
132 return scoped_ptr<WorkerThread>(); | |
133 return worker_thread; | |
134 } | |
135 | |
136 WorkerThread::~WorkerThread() { | |
137 DCHECK(should_exit_for_testing()); | |
138 } | |
139 | |
140 void WorkerThread::WakeUp() { | |
141 wake_up_event_.Signal(); | |
142 } | |
143 | |
144 scoped_refptr<SingleThreadTaskRunner> WorkerThread::CreateTaskRunnerWithTraits( | |
145 const TaskTraits& traits) { | |
146 // A WorkerThread is never destroyed, except in tests in which we don't use | |
147 // task runners after their WorkerThread has been destroyed. Because of that, | |
148 // it is correct to keep pointers to WorkerThread members in the constructed | |
149 // task runner. | |
150 return scoped_refptr<SingleThreadTaskRunner>( | |
151 new SchedulerSingleThreadTaskRunner( | |
152 traits, &single_thread_priority_queue_, task_tracker_)); | |
153 } | |
154 | |
155 void WorkerThread::JoinForTesting() { | |
156 should_exit_for_testing_ = true; | |
157 base::subtle::MemoryBarrier(); | |
158 WakeUp(); | |
159 PlatformThread::Join(thread_handle_); | |
160 } | |
161 | |
162 WorkerThread::WorkerThread(ThreadPriority thread_priority, | |
163 PriorityQueue* shared_priority_queue, | |
164 const SharedSequenceStillHasTasksCallback& | |
165 shared_sequence_still_has_tasks_callback, | |
166 const StateChangedCallback& state_changed_callback, | |
167 TaskTracker* task_tracker) | |
168 : wake_up_event_(false, false), | |
169 single_thread_priority_queue_( | |
170 Bind(&WorkerThread::WakeUp, Unretained(this)), | |
171 shared_priority_queue), | |
172 shared_priority_queue_(shared_priority_queue), | |
173 shared_sequence_still_has_tasks_callback_( | |
174 shared_sequence_still_has_tasks_callback), | |
175 state_changed_callback_(state_changed_callback), | |
176 task_tracker_(task_tracker) { | |
177 DCHECK(shared_priority_queue_); | |
178 DCHECK(!shared_sequence_still_has_tasks_callback_.is_null()); | |
179 DCHECK(!state_changed_callback_.is_null()); | |
180 DCHECK(task_tracker_); | |
181 | |
182 static const size_t kDefaultStackSize = 0; | |
183 PlatformThread::CreateWithPriority(kDefaultStackSize, this, &thread_handle_, | |
184 thread_priority); | |
185 } | |
186 | |
187 void WorkerThread::SetState(State state) { | |
188 DCHECK_NE(state_, state); | |
189 shared_priority_queue_->container_lock()->AssertAcquired(); | |
190 state_ = state; | |
191 state_changed_callback_.Run(this, state); | |
robliao
2016/03/30 00:42:42
I'm not sure I like this callback as we're holding
robliao
2016/03/30 00:47:28
This also means that the threadpool will have to m
fdoray
2016/03/30 18:44:49
I like the idea of delegating GetWork() to the Thr
| |
192 } | |
193 | |
194 void WorkerThread::ThreadMain() { | |
195 while (!task_tracker_->shutdown_completed() && !should_exit_for_testing()) { | |
196 // Get the sequence containing the next task to execute. | |
197 bool sequence_is_single_threaded = false; | |
198 scoped_refptr<Sequence> sequence; | |
199 { | |
200 scoped_ptr<PriorityQueue::Transaction> shared_transaction( | |
201 shared_priority_queue_->BeginTransaction()); | |
202 scoped_ptr<PriorityQueue::Transaction> single_thread_transaction( | |
203 single_thread_priority_queue_.BeginTransaction()); | |
204 sequence = | |
205 GetWork(shared_transaction.get(), single_thread_transaction.get(), | |
206 &sequence_is_single_threaded); | |
207 single_thread_transaction.reset(); | |
208 | |
209 if (!sequence) { | |
210 // Mark this WorkerThread as IDLE. This must be done within the scope of | |
211 // a |shared_priority_queue_| Transaction and |shared_priority_queue_| | |
212 // must be empty. | |
213 SetState(State::IDLE); | |
214 shared_transaction.reset(); | |
215 | |
216 // Wait for a wake-up. | |
217 wake_up_event_.Wait(); | |
robliao
2016/03/30 00:42:42
Between shared_transaction.reset and wake_up_event
fdoray
2016/03/30 18:44:49
Why is it problematic? What shouldn't happen betwe
robliao
2016/03/30 19:38:26
Previously, we had a CV do the work here so we cou
fdoray
2016/03/30 19:56:37
ok, I agree.
| |
218 | |
219 // Mark this WorkerThread as BUSY. This must be done within the scope of | |
220 // a |shared_priority_queue_| Transaction. | |
221 shared_transaction = shared_priority_queue_->BeginTransaction(); | |
222 SetState(State::BUSY); | |
223 | |
224 // Try to get work again. | |
225 continue; | |
226 } | |
227 } | |
228 | |
229 DCHECK_EQ(state_, State::BUSY); | |
230 | |
231 // Peek the next task in |sequence| and run it. | |
232 task_tracker_->RunTask(sequence->PeekTask()); | |
233 | |
234 // Pop a task from |sequence|. Reinsert it in the appropriate PriorityQueue | |
235 // if it's not empty. | |
236 if (!sequence->PopTask()) { | |
237 if (sequence_is_single_threaded) { | |
238 const SequenceSortKey sort_key = sequence->GetSortKey(); | |
239 single_thread_priority_queue_.BeginTransaction()->Push( | |
240 make_scoped_ptr(new PriorityQueue::SequenceAndSortKey( | |
241 std::move(sequence), sort_key))); | |
242 } else { | |
243 shared_sequence_still_has_tasks_callback_.Run(this, | |
244 std::move(sequence)); | |
245 } | |
246 } | |
247 | |
248 // Reset |wake_up_event_| to avoid an extra loop iteration before going to | |
249 // sleep if the PriorityQueues are empty. This WorkerThread will check its | |
250 // PriorityQueues and exit conditions at least once before going to sleep | |
251 // despite the fact that the event is reset here. | |
252 wake_up_event_.Reset(); | |
253 } | |
254 } | |
255 | |
256 std::ostream& operator<<(std::ostream& os, WorkerThread::State state) { | |
257 switch (state) { | |
258 case WorkerThread::State::BUSY: | |
259 os << "BUSY"; | |
260 break; | |
261 case WorkerThread::State::IDLE: | |
262 os << "IDLE"; | |
263 break; | |
264 } | |
265 return os; | |
266 } | |
267 | |
268 } // namespace internal | |
269 } // namespace base | |
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