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1 // Copyright 2013 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/message_loop/message_loop.h"
6 
7 #include <algorithm>
8 #include <utility>
9 
10 #include "base/bind.h"
11 #include "base/compiler_specific.h"
12 #include "base/lazy_instance.h"
13 #include "base/logging.h"
14 #include "base/memory/scoped_ptr.h"
15 #include "base/message_loop/message_pump_default.h"
16 #include "base/metrics/histogram.h"
17 #include "base/metrics/statistics_recorder.h"
18 #include "base/run_loop.h"
19 #include "base/thread_task_runner_handle.h"
20 #include "base/threading/thread_local.h"
21 #include "base/time/time.h"
22 #include "base/trace_event/trace_event.h"
23 #include "base/tracked_objects.h"
24 #include "build/build_config.h"
25 
26 #if defined(OS_MACOSX)
27 #include "base/message_loop/message_pump_mac.h"
28 #endif
29 #if defined(OS_POSIX) && !defined(OS_IOS)
30 #include "base/message_loop/message_pump_libevent.h"
31 #endif
32 #if defined(OS_ANDROID)
33 #include "base/message_loop/message_pump_android.h"
34 #endif
35 #if defined(USE_GLIB)
36 #include "base/message_loop/message_pump_glib.h"
37 #endif
38 
39 namespace base {
40 
41 namespace {
42 
43 // A lazily created thread local storage for quick access to a thread's message
44 // loop, if one exists.  This should be safe and free of static constructors.
45 LazyInstance<base::ThreadLocalPointer<MessageLoop> >::Leaky lazy_tls_ptr =
46     LAZY_INSTANCE_INITIALIZER;
47 
48 // Logical events for Histogram profiling. Run with --message-loop-histogrammer
49 // to get an accounting of messages and actions taken on each thread.
50 const int kTaskRunEvent = 0x1;
51 #if !defined(OS_NACL)
52 const int kTimerEvent = 0x2;
53 
54 // Provide range of message IDs for use in histogramming and debug display.
55 const int kLeastNonZeroMessageId = 1;
56 const int kMaxMessageId = 1099;
57 const int kNumberOfDistinctMessagesDisplayed = 1100;
58 
59 // Provide a macro that takes an expression (such as a constant, or macro
60 // constant) and creates a pair to initialize an array of pairs.  In this case,
61 // our pair consists of the expressions value, and the "stringized" version
62 // of the expression (i.e., the expression put in quotes).  For example, if
63 // we have:
64 //    #define FOO 2
65 //    #define BAR 5
66 // then the following:
67 //    VALUE_TO_NUMBER_AND_NAME(FOO + BAR)
68 // will expand to:
69 //   {7, "FOO + BAR"}
70 // We use the resulting array as an argument to our histogram, which reads the
71 // number as a bucket identifier, and proceeds to use the corresponding name
72 // in the pair (i.e., the quoted string) when printing out a histogram.
73 #define VALUE_TO_NUMBER_AND_NAME(name) {name, #name},
74 
75 const LinearHistogram::DescriptionPair event_descriptions_[] = {
76   // Provide some pretty print capability in our histogram for our internal
77   // messages.
78 
79   // A few events we handle (kindred to messages), and used to profile actions.
80   VALUE_TO_NUMBER_AND_NAME(kTaskRunEvent)
81   VALUE_TO_NUMBER_AND_NAME(kTimerEvent)
82 
83   {-1, NULL}  // The list must be null-terminated, per API to histogram.
84 };
85 #endif  // !defined(OS_NACL)
86 
87 bool enable_histogrammer_ = false;
88 
89 MessageLoop::MessagePumpFactory* message_pump_for_ui_factory_ = NULL;
90 
91 #if defined(OS_IOS)
92 typedef MessagePumpIOSForIO MessagePumpForIO;
93 #elif defined(OS_NACL_SFI)
94 typedef MessagePumpDefault MessagePumpForIO;
95 #elif defined(OS_POSIX)
96 typedef MessagePumpLibevent MessagePumpForIO;
97 #endif
98 
99 #if !defined(OS_NACL_SFI)
ToPumpIO(MessagePump * pump)100 MessagePumpForIO* ToPumpIO(MessagePump* pump) {
101   return static_cast<MessagePumpForIO*>(pump);
102 }
103 #endif  // !defined(OS_NACL_SFI)
104 
ReturnPump(scoped_ptr<MessagePump> pump)105 scoped_ptr<MessagePump> ReturnPump(scoped_ptr<MessagePump> pump) {
106   return pump;
107 }
108 
109 }  // namespace
110 
111 //------------------------------------------------------------------------------
112 
TaskObserver()113 MessageLoop::TaskObserver::TaskObserver() {
114 }
115 
~TaskObserver()116 MessageLoop::TaskObserver::~TaskObserver() {
117 }
118 
~DestructionObserver()119 MessageLoop::DestructionObserver::~DestructionObserver() {
120 }
121 
122 //------------------------------------------------------------------------------
123 
MessageLoop(Type type)124 MessageLoop::MessageLoop(Type type)
125     : MessageLoop(type, MessagePumpFactoryCallback()) {
126   BindToCurrentThread();
127 }
128 
MessageLoop(scoped_ptr<MessagePump> pump)129 MessageLoop::MessageLoop(scoped_ptr<MessagePump> pump)
130     : MessageLoop(TYPE_CUSTOM, Bind(&ReturnPump, Passed(&pump))) {
131   BindToCurrentThread();
132 }
133 
~MessageLoop()134 MessageLoop::~MessageLoop() {
135   // If |pump_| is non-null, this message loop has been bound and should be the
136   // current one on this thread. Otherwise, this loop is being destructed before
137   // it was bound to a thread, so a different message loop (or no loop at all)
138   // may be current.
139   DCHECK((pump_ && current() == this) || (!pump_ && current() != this));
140 
141   // iOS just attaches to the loop, it doesn't Run it.
142   // TODO(stuartmorgan): Consider wiring up a Detach().
143 #if !defined(OS_IOS)
144   DCHECK(!run_loop_);
145 #endif
146 
147 #if defined(OS_WIN)
148   if (in_high_res_mode_)
149     Time::ActivateHighResolutionTimer(false);
150 #endif
151   // Clean up any unprocessed tasks, but take care: deleting a task could
152   // result in the addition of more tasks (e.g., via DeleteSoon).  We set a
153   // limit on the number of times we will allow a deleted task to generate more
154   // tasks.  Normally, we should only pass through this loop once or twice.  If
155   // we end up hitting the loop limit, then it is probably due to one task that
156   // is being stubborn.  Inspect the queues to see who is left.
157   bool did_work;
158   for (int i = 0; i < 100; ++i) {
159     DeletePendingTasks();
160     ReloadWorkQueue();
161     // If we end up with empty queues, then break out of the loop.
162     did_work = DeletePendingTasks();
163     if (!did_work)
164       break;
165   }
166   DCHECK(!did_work);
167 
168   // Let interested parties have one last shot at accessing this.
169   FOR_EACH_OBSERVER(DestructionObserver, destruction_observers_,
170                     WillDestroyCurrentMessageLoop());
171 
172   thread_task_runner_handle_.reset();
173 
174   // Tell the incoming queue that we are dying.
175   incoming_task_queue_->WillDestroyCurrentMessageLoop();
176   incoming_task_queue_ = NULL;
177   unbound_task_runner_ = NULL;
178   task_runner_ = NULL;
179 
180   // OK, now make it so that no one can find us.
181   if (current() == this)
182     lazy_tls_ptr.Pointer()->Set(nullptr);
183 }
184 
185 // static
current()186 MessageLoop* MessageLoop::current() {
187   // TODO(darin): sadly, we cannot enable this yet since people call us even
188   // when they have no intention of using us.
189   // DCHECK(loop) << "Ouch, did you forget to initialize me?";
190   return lazy_tls_ptr.Pointer()->Get();
191 }
192 
193 // static
EnableHistogrammer(bool enable)194 void MessageLoop::EnableHistogrammer(bool enable) {
195   enable_histogrammer_ = enable;
196 }
197 
198 // static
InitMessagePumpForUIFactory(MessagePumpFactory * factory)199 bool MessageLoop::InitMessagePumpForUIFactory(MessagePumpFactory* factory) {
200   if (message_pump_for_ui_factory_)
201     return false;
202 
203   message_pump_for_ui_factory_ = factory;
204   return true;
205 }
206 
207 // static
CreateMessagePumpForType(Type type)208 scoped_ptr<MessagePump> MessageLoop::CreateMessagePumpForType(Type type) {
209 // TODO(rvargas): Get rid of the OS guards.
210 #if defined(USE_GLIB) && !defined(OS_NACL)
211   typedef MessagePumpGlib MessagePumpForUI;
212 #elif defined(OS_LINUX) && !defined(OS_NACL)
213   typedef MessagePumpLibevent MessagePumpForUI;
214 #endif
215 
216 #if defined(OS_IOS) || defined(OS_MACOSX)
217 #define MESSAGE_PUMP_UI scoped_ptr<MessagePump>(MessagePumpMac::Create())
218 #elif defined(OS_NACL)
219 // Currently NaCl doesn't have a UI MessageLoop.
220 // TODO(abarth): Figure out if we need this.
221 #define MESSAGE_PUMP_UI scoped_ptr<MessagePump>()
222 #else
223 #define MESSAGE_PUMP_UI scoped_ptr<MessagePump>(new MessagePumpForUI())
224 #endif
225 
226 #if defined(OS_MACOSX)
227   // Use an OS native runloop on Mac to support timer coalescing.
228   #define MESSAGE_PUMP_DEFAULT \
229       scoped_ptr<MessagePump>(new MessagePumpCFRunLoop())
230 #else
231   #define MESSAGE_PUMP_DEFAULT scoped_ptr<MessagePump>(new MessagePumpDefault())
232 #endif
233 
234   if (type == MessageLoop::TYPE_UI) {
235     if (message_pump_for_ui_factory_)
236       return message_pump_for_ui_factory_();
237     return MESSAGE_PUMP_UI;
238   }
239   if (type == MessageLoop::TYPE_IO)
240     return scoped_ptr<MessagePump>(new MessagePumpForIO());
241 
242 #if defined(OS_ANDROID)
243   if (type == MessageLoop::TYPE_JAVA)
244     return scoped_ptr<MessagePump>(new MessagePumpForUI());
245 #endif
246 
247   DCHECK_EQ(MessageLoop::TYPE_DEFAULT, type);
248   return MESSAGE_PUMP_DEFAULT;
249 }
250 
AddDestructionObserver(DestructionObserver * destruction_observer)251 void MessageLoop::AddDestructionObserver(
252     DestructionObserver* destruction_observer) {
253   DCHECK_EQ(this, current());
254   destruction_observers_.AddObserver(destruction_observer);
255 }
256 
RemoveDestructionObserver(DestructionObserver * destruction_observer)257 void MessageLoop::RemoveDestructionObserver(
258     DestructionObserver* destruction_observer) {
259   DCHECK_EQ(this, current());
260   destruction_observers_.RemoveObserver(destruction_observer);
261 }
262 
PostTask(const tracked_objects::Location & from_here,const Closure & task)263 void MessageLoop::PostTask(
264     const tracked_objects::Location& from_here,
265     const Closure& task) {
266   task_runner_->PostTask(from_here, task);
267 }
268 
PostDelayedTask(const tracked_objects::Location & from_here,const Closure & task,TimeDelta delay)269 void MessageLoop::PostDelayedTask(
270     const tracked_objects::Location& from_here,
271     const Closure& task,
272     TimeDelta delay) {
273   task_runner_->PostDelayedTask(from_here, task, delay);
274 }
275 
PostNonNestableTask(const tracked_objects::Location & from_here,const Closure & task)276 void MessageLoop::PostNonNestableTask(
277     const tracked_objects::Location& from_here,
278     const Closure& task) {
279   task_runner_->PostNonNestableTask(from_here, task);
280 }
281 
PostNonNestableDelayedTask(const tracked_objects::Location & from_here,const Closure & task,TimeDelta delay)282 void MessageLoop::PostNonNestableDelayedTask(
283     const tracked_objects::Location& from_here,
284     const Closure& task,
285     TimeDelta delay) {
286   task_runner_->PostNonNestableDelayedTask(from_here, task, delay);
287 }
288 
Run()289 void MessageLoop::Run() {
290   DCHECK(pump_);
291   RunLoop run_loop;
292   run_loop.Run();
293 }
294 
RunUntilIdle()295 void MessageLoop::RunUntilIdle() {
296   DCHECK(pump_);
297   RunLoop run_loop;
298   run_loop.RunUntilIdle();
299 }
300 
QuitWhenIdle()301 void MessageLoop::QuitWhenIdle() {
302   DCHECK_EQ(this, current());
303   if (run_loop_) {
304     run_loop_->quit_when_idle_received_ = true;
305   } else {
306     NOTREACHED() << "Must be inside Run to call Quit";
307   }
308 }
309 
QuitNow()310 void MessageLoop::QuitNow() {
311   DCHECK_EQ(this, current());
312   if (run_loop_) {
313     pump_->Quit();
314   } else {
315     NOTREACHED() << "Must be inside Run to call Quit";
316   }
317 }
318 
IsType(Type type) const319 bool MessageLoop::IsType(Type type) const {
320   return type_ == type;
321 }
322 
QuitCurrentWhenIdle()323 static void QuitCurrentWhenIdle() {
324   MessageLoop::current()->QuitWhenIdle();
325 }
326 
327 // static
QuitWhenIdleClosure()328 Closure MessageLoop::QuitWhenIdleClosure() {
329   return Bind(&QuitCurrentWhenIdle);
330 }
331 
SetNestableTasksAllowed(bool allowed)332 void MessageLoop::SetNestableTasksAllowed(bool allowed) {
333   if (allowed) {
334     // Kick the native pump just in case we enter a OS-driven nested message
335     // loop.
336     pump_->ScheduleWork();
337   }
338   nestable_tasks_allowed_ = allowed;
339 }
340 
NestableTasksAllowed() const341 bool MessageLoop::NestableTasksAllowed() const {
342   return nestable_tasks_allowed_;
343 }
344 
IsNested()345 bool MessageLoop::IsNested() {
346   return run_loop_->run_depth_ > 1;
347 }
348 
AddTaskObserver(TaskObserver * task_observer)349 void MessageLoop::AddTaskObserver(TaskObserver* task_observer) {
350   DCHECK_EQ(this, current());
351   task_observers_.AddObserver(task_observer);
352 }
353 
RemoveTaskObserver(TaskObserver * task_observer)354 void MessageLoop::RemoveTaskObserver(TaskObserver* task_observer) {
355   DCHECK_EQ(this, current());
356   task_observers_.RemoveObserver(task_observer);
357 }
358 
is_running() const359 bool MessageLoop::is_running() const {
360   DCHECK_EQ(this, current());
361   return run_loop_ != NULL;
362 }
363 
HasHighResolutionTasks()364 bool MessageLoop::HasHighResolutionTasks() {
365   return incoming_task_queue_->HasHighResolutionTasks();
366 }
367 
IsIdleForTesting()368 bool MessageLoop::IsIdleForTesting() {
369   // We only check the incoming queue, since we don't want to lock the work
370   // queue.
371   return incoming_task_queue_->IsIdleForTesting();
372 }
373 
374 //------------------------------------------------------------------------------
375 
376 // static
CreateUnbound(Type type,MessagePumpFactoryCallback pump_factory)377 scoped_ptr<MessageLoop> MessageLoop::CreateUnbound(
378     Type type, MessagePumpFactoryCallback pump_factory) {
379   return make_scoped_ptr(new MessageLoop(type, pump_factory));
380 }
381 
MessageLoop(Type type,MessagePumpFactoryCallback pump_factory)382 MessageLoop::MessageLoop(Type type, MessagePumpFactoryCallback pump_factory)
383     : type_(type),
384 #if defined(OS_WIN)
385       pending_high_res_tasks_(0),
386       in_high_res_mode_(false),
387 #endif
388       nestable_tasks_allowed_(true),
389 #if defined(OS_WIN)
390       os_modal_loop_(false),
391 #endif  // OS_WIN
392       pump_factory_(pump_factory),
393       message_histogram_(NULL),
394       run_loop_(NULL),
395       incoming_task_queue_(new internal::IncomingTaskQueue(this)),
396       unbound_task_runner_(
397           new internal::MessageLoopTaskRunner(incoming_task_queue_)),
398       task_runner_(unbound_task_runner_) {
399   // If type is TYPE_CUSTOM non-null pump_factory must be given.
400   DCHECK_EQ(type_ == TYPE_CUSTOM, !pump_factory_.is_null());
401 }
402 
BindToCurrentThread()403 void MessageLoop::BindToCurrentThread() {
404   DCHECK(!pump_);
405   if (!pump_factory_.is_null())
406     pump_ = pump_factory_.Run();
407   else
408     pump_ = CreateMessagePumpForType(type_);
409 
410   DCHECK(!current()) << "should only have one message loop per thread";
411   lazy_tls_ptr.Pointer()->Set(this);
412 
413   incoming_task_queue_->StartScheduling();
414   unbound_task_runner_->BindToCurrentThread();
415   unbound_task_runner_ = nullptr;
416   SetThreadTaskRunnerHandle();
417 }
418 
SetTaskRunner(scoped_refptr<SingleThreadTaskRunner> task_runner)419 void MessageLoop::SetTaskRunner(
420     scoped_refptr<SingleThreadTaskRunner> task_runner) {
421   DCHECK_EQ(this, current());
422   DCHECK(task_runner->BelongsToCurrentThread());
423   DCHECK(!unbound_task_runner_);
424   task_runner_ = std::move(task_runner);
425   SetThreadTaskRunnerHandle();
426 }
427 
SetThreadTaskRunnerHandle()428 void MessageLoop::SetThreadTaskRunnerHandle() {
429   DCHECK_EQ(this, current());
430   // Clear the previous thread task runner first, because only one can exist at
431   // a time.
432   thread_task_runner_handle_.reset();
433   thread_task_runner_handle_.reset(new ThreadTaskRunnerHandle(task_runner_));
434 }
435 
RunHandler()436 void MessageLoop::RunHandler() {
437   DCHECK_EQ(this, current());
438 
439   StartHistogrammer();
440 
441 #if defined(OS_WIN)
442   if (run_loop_->dispatcher_ && type() == TYPE_UI) {
443     static_cast<MessagePumpForUI*>(pump_.get())->
444         RunWithDispatcher(this, run_loop_->dispatcher_);
445     return;
446   }
447 #endif
448 
449   pump_->Run(this);
450 }
451 
ProcessNextDelayedNonNestableTask()452 bool MessageLoop::ProcessNextDelayedNonNestableTask() {
453   if (run_loop_->run_depth_ != 1)
454     return false;
455 
456   if (deferred_non_nestable_work_queue_.empty())
457     return false;
458 
459   PendingTask pending_task = deferred_non_nestable_work_queue_.front();
460   deferred_non_nestable_work_queue_.pop();
461 
462   RunTask(pending_task);
463   return true;
464 }
465 
RunTask(const PendingTask & pending_task)466 void MessageLoop::RunTask(const PendingTask& pending_task) {
467   DCHECK(nestable_tasks_allowed_);
468 
469 #if defined(OS_WIN)
470   if (pending_task.is_high_res) {
471     pending_high_res_tasks_--;
472     CHECK_GE(pending_high_res_tasks_, 0);
473   }
474 #endif
475 
476   // Execute the task and assume the worst: It is probably not reentrant.
477   nestable_tasks_allowed_ = false;
478 
479   HistogramEvent(kTaskRunEvent);
480 
481   TRACE_TASK_EXECUTION("MessageLoop::RunTask", pending_task);
482 
483   FOR_EACH_OBSERVER(TaskObserver, task_observers_,
484                     WillProcessTask(pending_task));
485   task_annotator_.RunTask("MessageLoop::PostTask", pending_task);
486   FOR_EACH_OBSERVER(TaskObserver, task_observers_,
487                     DidProcessTask(pending_task));
488 
489   nestable_tasks_allowed_ = true;
490 }
491 
DeferOrRunPendingTask(const PendingTask & pending_task)492 bool MessageLoop::DeferOrRunPendingTask(const PendingTask& pending_task) {
493   if (pending_task.nestable || run_loop_->run_depth_ == 1) {
494     RunTask(pending_task);
495     // Show that we ran a task (Note: a new one might arrive as a
496     // consequence!).
497     return true;
498   }
499 
500   // We couldn't run the task now because we're in a nested message loop
501   // and the task isn't nestable.
502   deferred_non_nestable_work_queue_.push(pending_task);
503   return false;
504 }
505 
AddToDelayedWorkQueue(const PendingTask & pending_task)506 void MessageLoop::AddToDelayedWorkQueue(const PendingTask& pending_task) {
507   // Move to the delayed work queue.
508   delayed_work_queue_.push(pending_task);
509 }
510 
DeletePendingTasks()511 bool MessageLoop::DeletePendingTasks() {
512   bool did_work = !work_queue_.empty();
513   while (!work_queue_.empty()) {
514     PendingTask pending_task = work_queue_.front();
515     work_queue_.pop();
516     if (!pending_task.delayed_run_time.is_null()) {
517       // We want to delete delayed tasks in the same order in which they would
518       // normally be deleted in case of any funny dependencies between delayed
519       // tasks.
520       AddToDelayedWorkQueue(pending_task);
521     }
522   }
523   did_work |= !deferred_non_nestable_work_queue_.empty();
524   while (!deferred_non_nestable_work_queue_.empty()) {
525     deferred_non_nestable_work_queue_.pop();
526   }
527   did_work |= !delayed_work_queue_.empty();
528 
529   // Historically, we always delete the task regardless of valgrind status. It's
530   // not completely clear why we want to leak them in the loops above.  This
531   // code is replicating legacy behavior, and should not be considered
532   // absolutely "correct" behavior.  See TODO above about deleting all tasks
533   // when it's safe.
534   while (!delayed_work_queue_.empty()) {
535     delayed_work_queue_.pop();
536   }
537   return did_work;
538 }
539 
ReloadWorkQueue()540 void MessageLoop::ReloadWorkQueue() {
541   // We can improve performance of our loading tasks from the incoming queue to
542   // |*work_queue| by waiting until the last minute (|*work_queue| is empty) to
543   // load. That reduces the number of locks-per-task significantly when our
544   // queues get large.
545   if (work_queue_.empty()) {
546 #if defined(OS_WIN)
547     pending_high_res_tasks_ +=
548         incoming_task_queue_->ReloadWorkQueue(&work_queue_);
549 #else
550     incoming_task_queue_->ReloadWorkQueue(&work_queue_);
551 #endif
552   }
553 }
554 
ScheduleWork()555 void MessageLoop::ScheduleWork() {
556   pump_->ScheduleWork();
557 }
558 
559 //------------------------------------------------------------------------------
560 // Method and data for histogramming events and actions taken by each instance
561 // on each thread.
562 
StartHistogrammer()563 void MessageLoop::StartHistogrammer() {
564 #if !defined(OS_NACL)  // NaCl build has no metrics code.
565   if (enable_histogrammer_ && !message_histogram_
566       && StatisticsRecorder::IsActive()) {
567     DCHECK(!thread_name_.empty());
568     message_histogram_ = LinearHistogram::FactoryGetWithRangeDescription(
569         "MsgLoop:" + thread_name_,
570         kLeastNonZeroMessageId, kMaxMessageId,
571         kNumberOfDistinctMessagesDisplayed,
572         HistogramBase::kHexRangePrintingFlag,
573         event_descriptions_);
574   }
575 #endif
576 }
577 
HistogramEvent(int event)578 void MessageLoop::HistogramEvent(int event) {
579 #if !defined(OS_NACL)
580   if (message_histogram_)
581     message_histogram_->Add(event);
582 #endif
583 }
584 
DoWork()585 bool MessageLoop::DoWork() {
586   if (!nestable_tasks_allowed_) {
587     // Task can't be executed right now.
588     return false;
589   }
590 
591   for (;;) {
592     ReloadWorkQueue();
593     if (work_queue_.empty())
594       break;
595 
596     // Execute oldest task.
597     do {
598       PendingTask pending_task = work_queue_.front();
599       work_queue_.pop();
600       if (!pending_task.delayed_run_time.is_null()) {
601         AddToDelayedWorkQueue(pending_task);
602         // If we changed the topmost task, then it is time to reschedule.
603         if (delayed_work_queue_.top().task.Equals(pending_task.task))
604           pump_->ScheduleDelayedWork(pending_task.delayed_run_time);
605       } else {
606         if (DeferOrRunPendingTask(pending_task))
607           return true;
608       }
609     } while (!work_queue_.empty());
610   }
611 
612   // Nothing happened.
613   return false;
614 }
615 
DoDelayedWork(TimeTicks * next_delayed_work_time)616 bool MessageLoop::DoDelayedWork(TimeTicks* next_delayed_work_time) {
617   if (!nestable_tasks_allowed_ || delayed_work_queue_.empty()) {
618     recent_time_ = *next_delayed_work_time = TimeTicks();
619     return false;
620   }
621 
622   // When we "fall behind", there will be a lot of tasks in the delayed work
623   // queue that are ready to run.  To increase efficiency when we fall behind,
624   // we will only call Time::Now() intermittently, and then process all tasks
625   // that are ready to run before calling it again.  As a result, the more we
626   // fall behind (and have a lot of ready-to-run delayed tasks), the more
627   // efficient we'll be at handling the tasks.
628 
629   TimeTicks next_run_time = delayed_work_queue_.top().delayed_run_time;
630   if (next_run_time > recent_time_) {
631     recent_time_ = TimeTicks::Now();  // Get a better view of Now();
632     if (next_run_time > recent_time_) {
633       *next_delayed_work_time = next_run_time;
634       return false;
635     }
636   }
637 
638   PendingTask pending_task = delayed_work_queue_.top();
639   delayed_work_queue_.pop();
640 
641   if (!delayed_work_queue_.empty())
642     *next_delayed_work_time = delayed_work_queue_.top().delayed_run_time;
643 
644   return DeferOrRunPendingTask(pending_task);
645 }
646 
DoIdleWork()647 bool MessageLoop::DoIdleWork() {
648   if (ProcessNextDelayedNonNestableTask())
649     return true;
650 
651   if (run_loop_->quit_when_idle_received_)
652     pump_->Quit();
653 
654   // When we return we will do a kernel wait for more tasks.
655 #if defined(OS_WIN)
656   // On Windows we activate the high resolution timer so that the wait
657   // _if_ triggered by the timer happens with good resolution. If we don't
658   // do this the default resolution is 15ms which might not be acceptable
659   // for some tasks.
660   bool high_res = pending_high_res_tasks_ > 0;
661   if (high_res != in_high_res_mode_) {
662     in_high_res_mode_ = high_res;
663     Time::ActivateHighResolutionTimer(in_high_res_mode_);
664   }
665 #endif
666   return false;
667 }
668 
DeleteSoonInternal(const tracked_objects::Location & from_here,void (* deleter)(const void *),const void * object)669 void MessageLoop::DeleteSoonInternal(const tracked_objects::Location& from_here,
670                                      void(*deleter)(const void*),
671                                      const void* object) {
672   PostNonNestableTask(from_here, Bind(deleter, object));
673 }
674 
ReleaseSoonInternal(const tracked_objects::Location & from_here,void (* releaser)(const void *),const void * object)675 void MessageLoop::ReleaseSoonInternal(
676     const tracked_objects::Location& from_here,
677     void(*releaser)(const void*),
678     const void* object) {
679   PostNonNestableTask(from_here, Bind(releaser, object));
680 }
681 
682 #if !defined(OS_NACL)
683 //------------------------------------------------------------------------------
684 // MessageLoopForUI
685 
686 #if defined(OS_ANDROID)
Start()687 void MessageLoopForUI::Start() {
688   // No Histogram support for UI message loop as it is managed by Java side
689   static_cast<MessagePumpForUI*>(pump_.get())->Start(this);
690 }
691 #endif
692 
693 #if defined(OS_IOS)
Attach()694 void MessageLoopForUI::Attach() {
695   static_cast<MessagePumpUIApplication*>(pump_.get())->Attach(this);
696 }
697 #endif
698 
699 #if defined(USE_OZONE) || (defined(USE_X11) && !defined(USE_GLIB))
WatchFileDescriptor(int fd,bool persistent,MessagePumpLibevent::Mode mode,MessagePumpLibevent::FileDescriptorWatcher * controller,MessagePumpLibevent::Watcher * delegate)700 bool MessageLoopForUI::WatchFileDescriptor(
701     int fd,
702     bool persistent,
703     MessagePumpLibevent::Mode mode,
704     MessagePumpLibevent::FileDescriptorWatcher *controller,
705     MessagePumpLibevent::Watcher *delegate) {
706   return static_cast<MessagePumpLibevent*>(pump_.get())->WatchFileDescriptor(
707       fd,
708       persistent,
709       mode,
710       controller,
711       delegate);
712 }
713 #endif
714 
715 #endif  // !defined(OS_NACL)
716 
717 //------------------------------------------------------------------------------
718 // MessageLoopForIO
719 
MessageLoopForIO()720 MessageLoopForIO::MessageLoopForIO() : MessageLoop(TYPE_IO) {}
721 
722 #if !defined(OS_NACL_SFI)
AddIOObserver(MessageLoopForIO::IOObserver * io_observer)723 void MessageLoopForIO::AddIOObserver(
724     MessageLoopForIO::IOObserver* io_observer) {
725   ToPumpIO(pump_.get())->AddIOObserver(io_observer);
726 }
727 
RemoveIOObserver(MessageLoopForIO::IOObserver * io_observer)728 void MessageLoopForIO::RemoveIOObserver(
729     MessageLoopForIO::IOObserver* io_observer) {
730   ToPumpIO(pump_.get())->RemoveIOObserver(io_observer);
731 }
732 
733 #if defined(OS_WIN)
RegisterIOHandler(HANDLE file,IOHandler * handler)734 void MessageLoopForIO::RegisterIOHandler(HANDLE file, IOHandler* handler) {
735   ToPumpIO(pump_.get())->RegisterIOHandler(file, handler);
736 }
737 
RegisterJobObject(HANDLE job,IOHandler * handler)738 bool MessageLoopForIO::RegisterJobObject(HANDLE job, IOHandler* handler) {
739   return ToPumpIO(pump_.get())->RegisterJobObject(job, handler);
740 }
741 
WaitForIOCompletion(DWORD timeout,IOHandler * filter)742 bool MessageLoopForIO::WaitForIOCompletion(DWORD timeout, IOHandler* filter) {
743   return ToPumpIO(pump_.get())->WaitForIOCompletion(timeout, filter);
744 }
745 #elif defined(OS_POSIX)
WatchFileDescriptor(int fd,bool persistent,Mode mode,FileDescriptorWatcher * controller,Watcher * delegate)746 bool MessageLoopForIO::WatchFileDescriptor(int fd,
747                                            bool persistent,
748                                            Mode mode,
749                                            FileDescriptorWatcher* controller,
750                                            Watcher* delegate) {
751   return ToPumpIO(pump_.get())->WatchFileDescriptor(
752       fd,
753       persistent,
754       mode,
755       controller,
756       delegate);
757 }
758 #endif
759 
760 #endif  // !defined(OS_NACL_SFI)
761 
762 }  // namespace base
763