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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "base/timer/timer.h" | 5 #include "base/timer/timer.h" |
6 | 6 |
7 #include <stddef.h> | 7 #include <stddef.h> |
8 | 8 |
9 #include <utility> | 9 #include <utility> |
10 | 10 |
11 #include "base/logging.h" | 11 #include "base/logging.h" |
12 #include "base/memory/ptr_util.h" | 12 #include "base/memory/ptr_util.h" |
13 #include "base/memory/ref_counted.h" | 13 #include "base/memory/ref_counted.h" |
14 #include "base/single_thread_task_runner.h" | 14 #include "base/sequenced_task_runner.h" |
15 #include "base/threading/platform_thread.h" | 15 #include "base/threading/sequenced_task_runner_handle.h" |
16 #include "base/threading/thread_task_runner_handle.h" | |
17 #include "base/time/tick_clock.h" | 16 #include "base/time/tick_clock.h" |
18 | 17 |
19 namespace base { | 18 namespace base { |
20 | 19 |
21 // BaseTimerTaskInternal is a simple delegate for scheduling a callback to | 20 // BaseTimerTaskInternal is a simple delegate for scheduling a callback to Timer |
vmpstr
2016/12/03 01:14:04
s/simple // :)
Can you also split up the comment
gab
2016/12/23 20:22:11
:)
| |
22 // Timer in the thread's default task runner. It also handles the following | 21 // in the destination task runner. It owns itself on the destination task |
23 // edge cases: | 22 // runner. If non-repeating, it will self-destruct when it fires otherwise it |
24 // - deleted by the task runner. | 23 // will re-enqueue until abandoned. If non-repeating it will also invoke |
25 // - abandoned (orphaned) by Timer. | 24 // |stop_callback| on |origin_task_runner| *before* running |task|. The WeakPtr |
26 class BaseTimerTaskInternal { | 25 // ensures that the task to trigger a self-destruction cancels all others. As |
26 // such, cancellation is racing with the scheduled delayed Run() task but so | |
vmpstr
2016/12/03 01:14:04
By race here, do you mean that either Abandon will
gab
2016/12/23 20:22:11
I mean that Abandon() is not a delayed task while
| |
27 // would any other cancellation method (e.g. using locks and sharing state with | |
28 // the origin task runner). An invariant assumed below is that there always is | |
29 // exactly one pending Run() task associated with this BaseTimerTaskInternal, as | |
30 // such only Run() needs to repost itself to maintain that invariant until self- | |
31 // destruction. | |
32 // | |
33 // Note: Timer and BaseTimerTaskInternal try to communicate synchronously when | |
34 // possible (i.e. when SetTaskRunner() wasn't used, which they can verify | |
35 // through RunsTasksOnCurrentThread()). Timer must also always use asynchronous | |
36 // calls when invoking Abandon() to avoid calling "delete this" from a reentrant | |
37 // call while handling Run(). | |
38 class BaseTimerTaskInternal : public SupportsWeakPtr<BaseTimerTaskInternal> { | |
27 public: | 39 public: |
28 explicit BaseTimerTaskInternal(Timer* timer) | 40 // A helper which invokes a Closure when destroyed. Required to notify |
29 : timer_(timer) { | 41 // BaseTimerTaskInternal when its Run() task is suppressed before it's |
30 } | 42 // scheduled (e.g. because the sequence is shutdown). Note: such cleanups |
31 | 43 // can't be bound directly to ~BaseTimerTaskInternal() as it owns itself (its |
32 ~BaseTimerTaskInternal() { | 44 // tasks use WeakPtrs and deleting them won't trigger |
33 // This task may be getting cleared because the task runner has been | 45 // ~BaseTimerTaskInternal()). |
34 // destructed. If so, don't leave Timer with a dangling pointer | 46 class CleanupTrigger { |
vmpstr
2016/12/03 01:14:04
Consider adding RunOnDestroy type of class to base
gab
2016/12/23 20:22:11
Whereelse? Tried to code search for it and didn't
| |
35 // to this. | 47 public: |
36 if (timer_) | 48 ~CleanupTrigger() { std::move(on_destruction_).Run(); } |
37 timer_->StopAndAbandon(); | 49 |
38 } | 50 private: |
39 | 51 friend class BaseTimerTaskInternal; |
40 void Run() { | 52 CleanupTrigger(OnceClosure on_destruction) |
41 // timer_ is NULL if we were abandoned. | 53 : on_destruction_(std::move(on_destruction)) {} |
42 if (!timer_) | 54 |
55 OnceClosure on_destruction_; | |
56 | |
57 DISALLOW_COPY_AND_ASSIGN(CleanupTrigger); | |
58 }; | |
59 | |
60 BaseTimerTaskInternal(const tracked_objects::Location& posted_from, | |
61 const Closure& task, | |
62 TimeDelta delay, | |
63 bool is_repeating, | |
64 TickClock* tick_clock, | |
65 scoped_refptr<SequencedTaskRunner> origin_task_runner, | |
66 const Closure& stop_callback) | |
67 : posted_from_(posted_from), | |
68 task_(task), | |
69 delay_(delay), | |
70 is_repeating_(is_repeating), | |
71 tick_clock_(tick_clock), | |
72 desired_run_time_(Now()), | |
73 origin_task_runner_(std::move(origin_task_runner)), | |
74 stop_callback_(stop_callback) { | |
75 destination_sequence_checker_.DetachFromSequence(); | |
vmpstr
2016/12/03 01:14:04
Can you comment that we need to detatch to ensure
gab
2016/12/23 20:22:11
Right, already have a comment to that effect on |d
| |
76 } | |
77 | |
78 ~BaseTimerTaskInternal() = default; | |
79 | |
80 void Run(std::unique_ptr<CleanupTrigger> cleanup_trigger) { | |
81 DCHECK(destination_sequence_checker_.CalledOnValidSequence()); | |
82 | |
83 const TimeDelta delay_remaining = desired_run_time_ - Now(); | |
84 if (delay_remaining > TimeDelta::FromMicroseconds(0)) { | |
85 #if DCHECK_IS_ON() | |
86 DCHECK(was_reset_) << delay_remaining; | |
87 #endif | |
88 SequencedTaskRunnerHandle::Get()->PostDelayedTask( | |
89 posted_from_, base::Bind(&BaseTimerTaskInternal::Run, AsWeakPtr(), | |
90 Passed(std::move(cleanup_trigger))), | |
91 delay_remaining); | |
43 return; | 92 return; |
44 | 93 } |
45 // *this will be deleted by the task runner, so Timer needs to | 94 |
46 // forget us: | 95 // Trigger cleanup before running the |task_|. e.g. to Stop() OneShotTimers |
47 timer_->scheduled_task_ = NULL; | 96 // so that anything posted from the task runs in the context of a stopped |
48 | 97 // timer as expected. |
49 // Although Timer should not call back into *this, let's clear | 98 if (!is_repeating_) |
50 // the timer_ member first to be pedantic. | 99 cleanup_trigger.reset(); |
51 Timer* timer = timer_; | 100 |
52 timer_ = NULL; | 101 task_.Run(); |
53 timer->RunScheduledTask(); | 102 |
54 } | 103 if (is_repeating_) { |
55 | 104 // TODO(gab): Currently rebasing on Now() to match prior status quo but |
vmpstr
2016/12/03 01:14:04
Can you file a bug for this and reference it here?
gab
2016/12/23 20:22:10
Done.
| |
56 // The task remains in the MessageLoop queue, but nothing will happen when it | 105 // think it would be better to merely |+= delay_| here to avoid the timer |
57 // runs. | 106 // drifting with the delayed task overhead. |
107 desired_run_time_ = Now() + delay_; | |
108 SequencedTaskRunnerHandle::Get()->PostDelayedTask( | |
109 posted_from_, base::Bind(&BaseTimerTaskInternal::Run, AsWeakPtr(), | |
110 Passed(std::move(cleanup_trigger))), | |
111 delay_); | |
vmpstr
2016/12/03 01:14:04
was_reset_ = false?
gab
2016/12/23 20:22:10
Done.
| |
112 } else { | |
113 delete this; | |
114 } | |
115 } | |
116 | |
117 // Postpones the |desired_run_time_| by |delay_|. | |
118 void Reset() { | |
119 DCHECK(destination_sequence_checker_.CalledOnValidSequence()); | |
120 DCHECK(!delay_.is_zero()); | |
121 | |
122 // Since this message is sent asynchronously, a few things might occur: | |
123 // - This is a one-shot timer and Run() hasn't occurred: | |
124 // postpone |desired_run_time_|, Run() will postpone itself when it | |
125 // runs. | |
126 // - This is a one-shot timer and Run() already occurred: | |
127 // Reset() came in too late and will be canceled via the WeakPtr. | |
128 // - This is a repeating timer and Run() has occurred zero to many times: | |
129 // postpone the next |desired_run_time_|. | |
130 // So overall, either the Reset() came in too late and will be canceled or | |
vmpstr
2016/12/03 01:14:04
This comment is a bit confusing to me. So does thi
gab
2016/12/23 20:22:11
This whole comment is just meant to say that altho
| |
131 // the |desired_run_time_| merely needs to be postponed. | |
132 | |
133 desired_run_time_ = Now() + delay_; | |
134 | |
135 #if DCHECK_IS_ON() | |
136 was_reset_ = true; | |
137 #endif | |
138 } | |
139 | |
58 void Abandon() { | 140 void Abandon() { |
59 timer_ = NULL; | 141 DCHECK(destination_sequence_checker_.CalledOnValidSequence()); |
142 | |
143 // Delete self, invalidating WeakPtrs and as such, pending Run()/Reset() | |
vmpstr
2016/12/03 01:14:04
Here as well, what's a reset task here?
gab
2016/12/23 20:22:11
Actually it can only cancel "the pending Run() tas
| |
144 // tasks. | |
145 delete this; | |
146 } | |
147 | |
148 std::unique_ptr<CleanupTrigger> GetCleanupTrigger() { | |
vmpstr
2016/12/03 01:14:04
nit: CreateCleanupTrigger
gab
2016/12/23 20:22:10
Done.
| |
149 // Note: it's important that CleanupTrigger's Closure be bound to a WeakPtr | |
150 // so that it only triggers if the Run() task is suppressed from its | |
151 // sequence while it was live (i.e. it shouldn't trigger when the task is | |
152 // destroyed because the WeakPtr was invalid when an abandoned Run() task | |
153 // was scheduled). | |
154 return WrapUnique( | |
155 new CleanupTrigger(Bind(&BaseTimerTaskInternal::Cleanup, AsWeakPtr()))); | |
60 } | 156 } |
61 | 157 |
62 private: | 158 private: |
63 Timer* timer_; | 159 TimeTicks Now() const { |
160 return tick_clock_ ? tick_clock_->NowTicks() : TimeTicks::Now(); | |
161 } | |
162 | |
163 // Cleans up state on the Timer side when this BaseTimerTaskInternal is done | |
164 // with its role. | |
165 void Cleanup() { | |
166 DCHECK(destination_sequence_checker_.CalledOnValidSequence()); | |
167 | |
168 if (origin_task_runner_->RunsTasksOnCurrentThread()) { | |
169 stop_callback_.Run(); | |
170 } else { | |
171 origin_task_runner_->PostTask(FROM_HERE, stop_callback_); | |
172 } | |
173 } | |
174 | |
175 const tracked_objects::Location posted_from_; | |
176 const Closure task_; | |
177 const TimeDelta delay_; | |
178 const bool is_repeating_; | |
179 | |
180 TickClock* tick_clock_; | |
181 TimeTicks desired_run_time_; | |
182 | |
183 const scoped_refptr<SequencedTaskRunner> origin_task_runner_; | |
184 const Closure stop_callback_; | |
185 | |
186 // Verifies that every operation (but construction) happens on the sequence | |
187 // where the task is intended to run. | |
188 SequenceChecker destination_sequence_checker_; | |
189 | |
190 #if DCHECK_IS_ON() | |
191 // Used to verify that reposts only occur when a Reset() was involved. | |
192 bool was_reset_ = false; | |
193 #endif | |
194 | |
195 DISALLOW_COPY_AND_ASSIGN(BaseTimerTaskInternal); | |
64 }; | 196 }; |
65 | 197 |
66 Timer::Timer(bool retain_user_task, bool is_repeating) | 198 Timer::Timer(bool retain_user_task, bool is_repeating) |
67 : Timer(retain_user_task, is_repeating, nullptr) {} | 199 : Timer(retain_user_task, is_repeating, nullptr) {} |
68 | 200 |
69 Timer::Timer(bool retain_user_task, bool is_repeating, TickClock* tick_clock) | 201 Timer::Timer(bool retain_user_task, bool is_repeating, TickClock* tick_clock) |
70 : scheduled_task_(nullptr), | 202 : is_repeating_(is_repeating), |
71 thread_id_(0), | |
72 is_repeating_(is_repeating), | |
73 retain_user_task_(retain_user_task), | 203 retain_user_task_(retain_user_task), |
74 tick_clock_(tick_clock), | 204 tick_clock_(tick_clock), |
75 is_running_(false) {} | 205 is_running_(false), |
206 weak_ptr_factory_(this) { | |
207 // It is safe for the timer to be created on a different thread/sequence than | |
208 // the one from which the timer APIs are called. The first call to the | |
209 // checker's CalledOnValidSequence() method will re-bind the checker, and | |
210 // later calls will verify that the same task runner is used. | |
211 origin_sequence_checker_.DetachFromSequence(); | |
212 } | |
76 | 213 |
77 Timer::Timer(const tracked_objects::Location& posted_from, | 214 Timer::Timer(const tracked_objects::Location& posted_from, |
78 TimeDelta delay, | 215 TimeDelta delay, |
79 const base::Closure& user_task, | 216 const base::Closure& user_task, |
80 bool is_repeating) | 217 bool is_repeating) |
81 : Timer(posted_from, delay, user_task, is_repeating, nullptr) {} | 218 : Timer(posted_from, delay, user_task, is_repeating, nullptr) {} |
82 | 219 |
83 Timer::Timer(const tracked_objects::Location& posted_from, | 220 Timer::Timer(const tracked_objects::Location& posted_from, |
84 TimeDelta delay, | 221 TimeDelta delay, |
85 const base::Closure& user_task, | 222 const base::Closure& user_task, |
86 bool is_repeating, | 223 bool is_repeating, |
87 TickClock* tick_clock) | 224 TickClock* tick_clock) |
88 : scheduled_task_(nullptr), | 225 : posted_from_(posted_from), |
89 posted_from_(posted_from), | |
90 delay_(delay), | 226 delay_(delay), |
91 user_task_(user_task), | 227 user_task_(user_task), |
92 thread_id_(0), | |
93 is_repeating_(is_repeating), | 228 is_repeating_(is_repeating), |
94 retain_user_task_(true), | 229 retain_user_task_(true), |
95 tick_clock_(tick_clock), | 230 tick_clock_(tick_clock), |
96 is_running_(false) {} | 231 is_running_(false), |
232 weak_ptr_factory_(this) { | |
233 // See comment in other constructor. | |
234 origin_sequence_checker_.DetachFromSequence(); | |
235 } | |
97 | 236 |
98 Timer::~Timer() { | 237 Timer::~Timer() { |
99 StopAndAbandon(); | 238 if (origin_sequence_checker_.CalledOnValidSequence()) { |
vmpstr
2016/12/03 01:14:04
This is changing code behavior based on whether DC
gab
2016/12/23 20:22:10
No it doesn't because the member is a SequenceChec
| |
239 Stop(); | |
240 } else { | |
241 // As highlighted in the constructor. It's okay to start the Timer on a | |
242 // different sequence but it must then be sequentially stopped on that | |
243 // sequence as well before it can be deleted on its original sequence. | |
244 DCHECK(!is_running_); | |
245 } | |
100 } | 246 } |
101 | 247 |
102 bool Timer::IsRunning() const { | 248 bool Timer::IsRunning() const { |
249 DCHECK(origin_sequence_checker_.CalledOnValidSequence()); | |
103 return is_running_; | 250 return is_running_; |
104 } | 251 } |
105 | 252 |
106 TimeDelta Timer::GetCurrentDelay() const { | 253 TimeDelta Timer::GetCurrentDelay() const { |
254 DCHECK(origin_sequence_checker_.CalledOnValidSequence()); | |
107 return delay_; | 255 return delay_; |
108 } | 256 } |
109 | 257 |
110 void Timer::SetTaskRunner(scoped_refptr<SingleThreadTaskRunner> task_runner) { | 258 void Timer::SetTaskRunner(scoped_refptr<SequencedTaskRunner> task_runner) { |
111 // Do not allow changing the task runner once something has been scheduled. | 259 DCHECK(origin_sequence_checker_.CalledOnValidSequence()); |
112 DCHECK_EQ(thread_id_, 0); | 260 |
113 task_runner_.swap(task_runner); | 261 // Do not allow changing the task runner while something is been scheduled. |
vmpstr
2016/12/03 01:14:04
s/been //
gab
2016/12/23 20:22:11
Done.
| |
262 DCHECK(!is_running_); | |
263 destination_task_runner_ = std::move(task_runner); | |
114 } | 264 } |
115 | 265 |
116 void Timer::Start(const tracked_objects::Location& posted_from, | 266 void Timer::Start(const tracked_objects::Location& posted_from, |
117 TimeDelta delay, | 267 TimeDelta delay, |
118 const base::Closure& user_task) { | 268 const base::Closure& user_task) { |
269 DCHECK(origin_sequence_checker_.CalledOnValidSequence()); | |
270 | |
271 // Do a best-effort to cancel the previous task, it may still racily fire | |
272 // though. | |
273 AbandonScheduledTask(); | |
274 | |
119 SetTaskInfo(posted_from, delay, user_task); | 275 SetTaskInfo(posted_from, delay, user_task); |
120 Reset(); | 276 Reset(); |
vmpstr
2016/12/03 01:14:04
Is this call always just PostNewScheduledTask?
gab
2016/12/23 20:22:11
Actually yes it is, inlined that instead and added
| |
121 } | 277 } |
122 | 278 |
123 void Timer::Stop() { | 279 void Timer::Stop() { |
124 is_running_ = false; | 280 DCHECK(origin_sequence_checker_.CalledOnValidSequence()); |
281 | |
282 AbandonScheduledTask(); | |
125 if (!retain_user_task_) | 283 if (!retain_user_task_) |
126 user_task_.Reset(); | 284 user_task_.Reset(); |
127 } | 285 } |
128 | 286 |
129 void Timer::Reset() { | 287 void Timer::Reset() { |
288 DCHECK(origin_sequence_checker_.CalledOnValidSequence()); | |
130 DCHECK(!user_task_.is_null()); | 289 DCHECK(!user_task_.is_null()); |
131 | 290 |
132 // If there's no pending task, start one up and return. | 291 if (is_running_) { |
133 if (!scheduled_task_) { | 292 if (destination_task_runner_) { |
293 destination_task_runner_->PostTask( | |
294 FROM_HERE, | |
295 base::Bind(&BaseTimerTaskInternal::Reset, scheduled_task_weak_ref_)); | |
296 } else { | |
297 // |is_running_| guarantees a valid pointer when not using an external | |
298 // |destination_task_runner_|. | |
299 DCHECK(scheduled_task_weak_ref_); | |
300 scheduled_task_weak_ref_->Reset(); | |
301 } | |
302 } else { | |
134 PostNewScheduledTask(delay_); | 303 PostNewScheduledTask(delay_); |
vmpstr
2016/12/03 01:14:04
It's unclear to me if there other call sites other
gab
2016/12/23 20:22:11
The API is a bit of a mess but yes this is require
| |
135 return; | |
136 } | 304 } |
137 | |
138 // Set the new desired_run_time_. | |
139 if (delay_ > TimeDelta::FromMicroseconds(0)) | |
140 desired_run_time_ = Now() + delay_; | |
141 else | |
142 desired_run_time_ = TimeTicks(); | |
143 | |
144 // We can use the existing scheduled task if it arrives before the new | |
145 // desired_run_time_. | |
146 if (desired_run_time_ >= scheduled_run_time_) { | |
147 is_running_ = true; | |
148 return; | |
149 } | |
150 | |
151 // We can't reuse the scheduled_task_, so abandon it and post a new one. | |
152 AbandonScheduledTask(); | |
153 PostNewScheduledTask(delay_); | |
154 } | 305 } |
155 | 306 |
156 TimeTicks Timer::Now() const { | 307 TimeTicks Timer::Now() const { |
157 return tick_clock_ ? tick_clock_->NowTicks() : TimeTicks::Now(); | 308 return tick_clock_ ? tick_clock_->NowTicks() : TimeTicks::Now(); |
158 } | 309 } |
159 | 310 |
160 void Timer::SetTaskInfo(const tracked_objects::Location& posted_from, | 311 void Timer::SetTaskInfo(const tracked_objects::Location& posted_from, |
161 TimeDelta delay, | 312 TimeDelta delay, |
162 const base::Closure& user_task) { | 313 const base::Closure& user_task) { |
314 DCHECK(origin_sequence_checker_.CalledOnValidSequence()); | |
315 DCHECK(!is_running_); | |
316 | |
163 posted_from_ = posted_from; | 317 posted_from_ = posted_from; |
164 delay_ = delay; | 318 delay_ = delay; |
165 user_task_ = user_task; | 319 user_task_ = user_task; |
166 } | 320 } |
167 | 321 |
168 void Timer::PostNewScheduledTask(TimeDelta delay) { | 322 void Timer::PostNewScheduledTask(TimeDelta delay) { |
169 DCHECK(scheduled_task_ == NULL); | 323 DCHECK(origin_sequence_checker_.CalledOnValidSequence()); |
324 DCHECK(SequencedTaskRunnerHandle::IsSet()); | |
325 | |
326 scoped_refptr<SequencedTaskRunner> destination_task_runner = | |
327 destination_task_runner_ ? destination_task_runner_ | |
328 : SequencedTaskRunnerHandle::Get(); | |
329 | |
170 is_running_ = true; | 330 is_running_ = true; |
171 scheduled_task_ = new BaseTimerTaskInternal(this); | 331 BaseTimerTaskInternal* scheduled_task = new BaseTimerTaskInternal( |
172 if (delay > TimeDelta::FromMicroseconds(0)) { | 332 posted_from_, user_task_, delay, is_repeating_, tick_clock_, |
173 GetTaskRunner()->PostDelayedTask(posted_from_, | 333 SequencedTaskRunnerHandle::Get(), |
174 base::Bind(&BaseTimerTaskInternal::Run, base::Owned(scheduled_task_)), | 334 base::Bind(&Timer::Stop, weak_ptr_factory_.GetWeakPtr())); |
175 delay); | 335 scheduled_task_weak_ref_ = scheduled_task->AsWeakPtr(); |
176 scheduled_run_time_ = desired_run_time_ = Now() + delay; | 336 destination_task_runner->PostDelayedTask( |
177 } else { | 337 posted_from_, |
178 GetTaskRunner()->PostTask(posted_from_, | 338 base::Bind(&BaseTimerTaskInternal::Run, scheduled_task_weak_ref_, |
179 base::Bind(&BaseTimerTaskInternal::Run, base::Owned(scheduled_task_))); | 339 Passed(scheduled_task->GetCleanupTrigger())), |
180 scheduled_run_time_ = desired_run_time_ = TimeTicks(); | 340 delay); |
181 } | |
182 // Remember the thread ID that posts the first task -- this will be verified | |
183 // later when the task is abandoned to detect misuse from multiple threads. | |
184 if (!thread_id_) | |
185 thread_id_ = static_cast<int>(PlatformThread::CurrentId()); | |
186 } | |
187 | |
188 scoped_refptr<SingleThreadTaskRunner> Timer::GetTaskRunner() { | |
189 return task_runner_.get() ? task_runner_ : ThreadTaskRunnerHandle::Get(); | |
190 } | 341 } |
191 | 342 |
192 void Timer::AbandonScheduledTask() { | 343 void Timer::AbandonScheduledTask() { |
193 DCHECK(thread_id_ == 0 || | 344 DCHECK(origin_sequence_checker_.CalledOnValidSequence()); |
194 thread_id_ == static_cast<int>(PlatformThread::CurrentId())); | 345 |
195 if (scheduled_task_) { | 346 if (is_running_) { |
196 scheduled_task_->Abandon(); | 347 // Toggle |is_running| first to be reentrancy safe, just in case. |
197 scheduled_task_ = NULL; | 348 is_running_ = false; |
349 | |
350 const Closure abandon = | |
351 base::Bind(&BaseTimerTaskInternal::Abandon, scheduled_task_weak_ref_); | |
352 if (destination_task_runner_) { | |
353 destination_task_runner_->PostTask(FROM_HERE, abandon); | |
354 } else if (SequencedTaskRunnerHandle::IsSet()) { | |
355 // Post Abandon() as an asynchronous call to avoid deleting | |
356 // BaseTimerTaskInternal while it handles Run() (reentrancy is possible, | |
357 // e.g. when the task itself deletes the Timer or when a OneShotTimer's | |
358 // BaseTimerTaskInternal::Run() invoked its |stop_callback_|). | |
359 SequencedTaskRunnerHandle::Get()->PostTask(FROM_HERE, abandon); | |
360 } else { | |
361 // |is_running_| guarantees a valid pointer when not using an external | |
362 // |destination_task_runner_|. | |
363 DCHECK(scheduled_task_weak_ref_); | |
364 // The reentrancy situations described above happen while Run() is active | |
365 // which implies SequencedTaskRunnerHandle::IsSet(). | |
366 // SequencedTaskRunnerHandle not being set typically means this | |
367 // AbandonScheduledTask() was triggered by ~Timer() on shutdown in which | |
368 // case it's safe to synchronously abandon on sequence. | |
369 scheduled_task_weak_ref_->Abandon(); | |
370 } | |
371 scheduled_task_weak_ref_ = nullptr; | |
198 } | 372 } |
199 } | 373 } |
200 | 374 |
201 void Timer::RunScheduledTask() { | |
202 // Task may have been disabled. | |
203 if (!is_running_) | |
204 return; | |
205 | |
206 // First check if we need to delay the task because of a new target time. | |
207 if (desired_run_time_ > scheduled_run_time_) { | |
208 // Now() can be expensive, so only call it if we know the user has changed | |
209 // the desired_run_time_. | |
210 TimeTicks now = Now(); | |
211 // Task runner may have called us late anyway, so only post a continuation | |
212 // task if the desired_run_time_ is in the future. | |
213 if (desired_run_time_ > now) { | |
214 // Post a new task to span the remaining time. | |
215 PostNewScheduledTask(desired_run_time_ - now); | |
216 return; | |
217 } | |
218 } | |
219 | |
220 // Make a local copy of the task to run. The Stop method will reset the | |
221 // user_task_ member if retain_user_task_ is false. | |
222 base::Closure task = user_task_; | |
223 | |
224 if (is_repeating_) | |
225 PostNewScheduledTask(delay_); | |
226 else | |
227 Stop(); | |
228 | |
229 task.Run(); | |
230 | |
231 // No more member accesses here: *this could be deleted at this point. | |
232 } | |
233 | |
234 } // namespace base | 375 } // namespace base |
OLD | NEW |