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/incoming_task_queue.h"
6
7 #include "base/debug/trace_event.h"
8 #include "base/location.h"
9 #include "base/message_loop/message_loop.h"
10 #include "base/synchronization/waitable_event.h"
11
12 namespace base {
13 namespace internal {
14
IncomingTaskQueue(MessageLoop * message_loop)15 IncomingTaskQueue::IncomingTaskQueue(MessageLoop* message_loop)
16 : message_loop_(message_loop),
17 next_sequence_num_(0) {
18 }
19
AddToIncomingQueue(const tracked_objects::Location & from_here,const Closure & task,TimeDelta delay,bool nestable)20 bool IncomingTaskQueue::AddToIncomingQueue(
21 const tracked_objects::Location& from_here,
22 const Closure& task,
23 TimeDelta delay,
24 bool nestable) {
25 AutoLock locked(incoming_queue_lock_);
26 PendingTask pending_task(
27 from_here, task, CalculateDelayedRuntime(delay), nestable);
28 return PostPendingTask(&pending_task);
29 }
30
IsHighResolutionTimerEnabledForTesting()31 bool IncomingTaskQueue::IsHighResolutionTimerEnabledForTesting() {
32 #if defined(OS_WIN)
33 return !high_resolution_timer_expiration_.is_null();
34 #else
35 return true;
36 #endif
37 }
38
IsIdleForTesting()39 bool IncomingTaskQueue::IsIdleForTesting() {
40 AutoLock lock(incoming_queue_lock_);
41 return incoming_queue_.empty();
42 }
43
ReloadWorkQueue(TaskQueue * work_queue)44 void IncomingTaskQueue::ReloadWorkQueue(TaskQueue* work_queue) {
45 // Make sure no tasks are lost.
46 DCHECK(work_queue->empty());
47
48 // Acquire all we can from the inter-thread queue with one lock acquisition.
49 AutoLock lock(incoming_queue_lock_);
50 if (!incoming_queue_.empty())
51 incoming_queue_.Swap(work_queue); // Constant time
52
53 DCHECK(incoming_queue_.empty());
54 }
55
WillDestroyCurrentMessageLoop()56 void IncomingTaskQueue::WillDestroyCurrentMessageLoop() {
57 #if defined(OS_WIN)
58 // If we left the high-resolution timer activated, deactivate it now.
59 // Doing this is not-critical, it is mainly to make sure we track
60 // the high resolution timer activations properly in our unit tests.
61 if (!high_resolution_timer_expiration_.is_null()) {
62 Time::ActivateHighResolutionTimer(false);
63 high_resolution_timer_expiration_ = TimeTicks();
64 }
65 #endif
66
67 AutoLock lock(incoming_queue_lock_);
68 message_loop_ = NULL;
69 }
70
~IncomingTaskQueue()71 IncomingTaskQueue::~IncomingTaskQueue() {
72 // Verify that WillDestroyCurrentMessageLoop() has been called.
73 DCHECK(!message_loop_);
74 }
75
CalculateDelayedRuntime(TimeDelta delay)76 TimeTicks IncomingTaskQueue::CalculateDelayedRuntime(TimeDelta delay) {
77 TimeTicks delayed_run_time;
78 if (delay > TimeDelta()) {
79 delayed_run_time = TimeTicks::Now() + delay;
80
81 #if defined(OS_WIN)
82 if (high_resolution_timer_expiration_.is_null()) {
83 // Windows timers are granular to 15.6ms. If we only set high-res
84 // timers for those under 15.6ms, then a 18ms timer ticks at ~32ms,
85 // which as a percentage is pretty inaccurate. So enable high
86 // res timers for any timer which is within 2x of the granularity.
87 // This is a tradeoff between accuracy and power management.
88 bool needs_high_res_timers = delay.InMilliseconds() <
89 (2 * Time::kMinLowResolutionThresholdMs);
90 if (needs_high_res_timers) {
91 if (Time::ActivateHighResolutionTimer(true)) {
92 high_resolution_timer_expiration_ = TimeTicks::Now() +
93 TimeDelta::FromMilliseconds(
94 MessageLoop::kHighResolutionTimerModeLeaseTimeMs);
95 }
96 }
97 }
98 #endif
99 } else {
100 DCHECK_EQ(delay.InMilliseconds(), 0) << "delay should not be negative";
101 }
102
103 #if defined(OS_WIN)
104 if (!high_resolution_timer_expiration_.is_null()) {
105 if (TimeTicks::Now() > high_resolution_timer_expiration_) {
106 Time::ActivateHighResolutionTimer(false);
107 high_resolution_timer_expiration_ = TimeTicks();
108 }
109 }
110 #endif
111
112 return delayed_run_time;
113 }
114
PostPendingTask(PendingTask * pending_task)115 bool IncomingTaskQueue::PostPendingTask(PendingTask* pending_task) {
116 // Warning: Don't try to short-circuit, and handle this thread's tasks more
117 // directly, as it could starve handling of foreign threads. Put every task
118 // into this queue.
119
120 // This should only be called while the lock is taken.
121 incoming_queue_lock_.AssertAcquired();
122
123 if (!message_loop_) {
124 pending_task->task.Reset();
125 return false;
126 }
127
128 // Initialize the sequence number. The sequence number is used for delayed
129 // tasks (to faciliate FIFO sorting when two tasks have the same
130 // delayed_run_time value) and for identifying the task in about:tracing.
131 pending_task->sequence_num = next_sequence_num_++;
132
133 TRACE_EVENT_FLOW_BEGIN0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
134 "MessageLoop::PostTask",
135 TRACE_ID_MANGLE(message_loop_->GetTaskTraceID(*pending_task)));
136
137 bool was_empty = incoming_queue_.empty();
138 incoming_queue_.push(*pending_task);
139 pending_task->task.Reset();
140
141 // Wake up the pump.
142 message_loop_->ScheduleWork(was_empty);
143
144 return true;
145 }
146
147 } // namespace internal
148 } // namespace base
149