base/message_loop/incoming_task_queue.cc

   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 <limits>
   8
   9 #include "base/location.h"
  10 #include "base/message_loop/message_loop.h"
  11 #include "base/metrics/histogram.h"
  12 #include "base/synchronization/waitable_event.h"
  13 #include "base/time/time.h"
  14
  15 namespace base {
  16 namespace internal {
  17
  18 namespace {
  19
  20 #ifndef NDEBUG
  21 // Delays larger than this are often bogus, and a warning should be emitted in
  22 // debug builds to warn developers.  http://crbug.com/450045
  23 const int kTaskDelayWarningThresholdInSeconds =
  24     14 * 24 * 60 * 60;  // 14 days.
  25 #endif
  26
  27 // Returns true if MessagePump::ScheduleWork() must be called one
  28 // time for every task that is added to the MessageLoop incoming queue.
  29 bool AlwaysNotifyPump(MessageLoop::Type type) {
  30 #if defined(OS_ANDROID)
  31   // The Android UI message loop needs to get notified each time a task is
  32   // added
  33   // to the incoming queue.
  34   return type == MessageLoop::TYPE_UI || type == MessageLoop::TYPE_JAVA;
  35 #else
  36   return false;
  37 #endif
  38 }
  39
  40 }  // namespace
  41
  42 IncomingTaskQueue::IncomingTaskQueue(MessageLoop* message_loop)
  43     : high_res_task_count_(0),
  44       message_loop_(message_loop),
  45       next_sequence_num_(0),
  46       message_loop_scheduled_(false),
  47       always_schedule_work_(AlwaysNotifyPump(message_loop_->type())) {
  48 }
  49
  50 bool IncomingTaskQueue::AddToIncomingQueue(
  51     const tracked_objects::Location& from_here,
  52     const Closure& task,
  53     TimeDelta delay,
  54     bool nestable) {
  55   DLOG_IF(WARNING,
  56           delay.InSeconds() > kTaskDelayWarningThresholdInSeconds)
  57       << "Requesting super-long task delay period of " << delay.InSeconds()
  58       << " seconds from here: " << from_here.ToString();
  59
  60   AutoLock locked(incoming_queue_lock_);
  61   PendingTask pending_task(
  62       from_here, task, CalculateDelayedRuntime(delay), nestable);
  63 #if defined(OS_WIN)
  64   // We consider the task needs a high resolution timer if the delay is
  65   // more than 0 and less than 32ms. This caps the relative error to
  66   // less than 50% : a 33ms wait can wake at 48ms since the default
  67   // resolution on Windows is between 10 and 15ms.
  68   if (delay > TimeDelta() &&
  69       delay.InMilliseconds() < (2 * Time::kMinLowResolutionThresholdMs)) {
  70     ++high_res_task_count_;
  71     pending_task.is_high_res = true;
  72   }
  73 #endif
  74   return PostPendingTask(&pending_task);
  75 }
  76
  77 bool IncomingTaskQueue::HasHighResolutionTasks() {
  78   AutoLock lock(incoming_queue_lock_);
  79   return high_res_task_count_ > 0;
  80 }
  81
  82 bool IncomingTaskQueue::IsIdleForTesting() {
  83   AutoLock lock(incoming_queue_lock_);
  84   return incoming_queue_.empty();
  85 }
  86
  87 int IncomingTaskQueue::ReloadWorkQueue(TaskQueue* work_queue) {
  88   // Make sure no tasks are lost.
  89   DCHECK(work_queue->empty());
  90
  91   // Acquire all we can from the inter-thread queue with one lock acquisition.
  92   AutoLock lock(incoming_queue_lock_);
  93   if (incoming_queue_.empty()) {
  94     // If the loop attempts to reload but there are no tasks in the incoming
  95     // queue, that means it will go to sleep waiting for more work. If the
  96     // incoming queue becomes nonempty we need to schedule it again.
  97     message_loop_scheduled_ = false;
  98   } else {
  99     incoming_queue_.Swap(work_queue);
 100   }
 101   // Reset the count of high resolution tasks since our queue is now empty.
 102   int high_res_tasks = high_res_task_count_;
 103   high_res_task_count_ = 0;
 104   return high_res_tasks;
 105 }
 106
 107 void IncomingTaskQueue::WillDestroyCurrentMessageLoop() {
 108   AutoLock lock(incoming_queue_lock_);
 109   message_loop_ = NULL;
 110 }
 111
 112 IncomingTaskQueue::~IncomingTaskQueue() {
 113   // Verify that WillDestroyCurrentMessageLoop() has been called.
 114   DCHECK(!message_loop_);
 115 }
 116
 117 TimeTicks IncomingTaskQueue::CalculateDelayedRuntime(TimeDelta delay) {
 118   TimeTicks delayed_run_time;
 119   if (delay > TimeDelta())
 120     delayed_run_time = TimeTicks::Now() + delay;
 121   else
 122     DCHECK_EQ(delay.InMilliseconds(), 0) << "delay should not be negative";
 123   return delayed_run_time;
 124 }
 125
 126 bool IncomingTaskQueue::PostPendingTask(PendingTask* pending_task) {
 127   // Warning: Don't try to short-circuit, and handle this thread's tasks more
 128   // directly, as it could starve handling of foreign threads.  Put every task
 129   // into this queue.
 130
 131   // This should only be called while the lock is taken.
 132   incoming_queue_lock_.AssertAcquired();
 133
 134   if (!message_loop_) {
 135     pending_task->task.Reset();
 136     return false;
 137   }
 138
 139   // Initialize the sequence number. The sequence number is used for delayed
 140   // tasks (to faciliate FIFO sorting when two tasks have the same
 141   // delayed_run_time value) and for identifying the task in about:tracing.
 142   pending_task->sequence_num = next_sequence_num_++;
 143
 144   message_loop_->task_annotator()->DidQueueTask("MessageLoop::PostTask",
 145                                                 *pending_task);
 146
 147   bool was_empty = incoming_queue_.empty();
 148   incoming_queue_.push(*pending_task);
 149   pending_task->task.Reset();
 150
 151   if (always_schedule_work_ || (!message_loop_scheduled_ && was_empty)) {
 152     // Wake up the message loop.
 153     message_loop_->ScheduleWork();
 154     // After we've scheduled the message loop, we do not need to do so again
 155     // until we know it has processed all of the work in our queue and is
 156     // waiting for more work again. The message loop will always attempt to
 157     // reload from the incoming queue before waiting again so we clear this flag
 158     // in ReloadWorkQueue().
 159     message_loop_scheduled_ = true;
 160   }
 161
 162   return true;
 163 }
 164
 165 }  // namespace internal
 166 }  // namespace base