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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/message_loop/incoming_task_queue.h"
#include <limits>
#include <utility>
#include "base/location.h"
#include "base/message_loop/message_loop.h"
#include "base/synchronization/waitable_event.h"
#include "base/time/time.h"
#include "build/build_config.h"
namespace base {
namespace internal {
namespace {
#if DCHECK_IS_ON()
// Delays larger than this are often bogus, and a warning should be emitted in
// debug builds to warn developers. http://crbug.com/450045
const int kTaskDelayWarningThresholdInSeconds =
14 * 24 * 60 * 60; // 14 days.
#endif
// Returns true if MessagePump::ScheduleWork() must be called one
// time for every task that is added to the MessageLoop incoming queue.
bool AlwaysNotifyPump(MessageLoop::Type type) {
#if defined(OS_ANDROID)
// The Android UI message loop needs to get notified each time a task is
// added
// to the incoming queue.
return type == MessageLoop::TYPE_UI || type == MessageLoop::TYPE_JAVA;
#else
return false;
#endif
}
TimeTicks CalculateDelayedRuntime(TimeDelta delay) {
TimeTicks delayed_run_time;
if (delay > TimeDelta())
delayed_run_time = TimeTicks::Now() + delay;
else
DCHECK_EQ(delay.InMilliseconds(), 0) << "delay should not be negative";
return delayed_run_time;
}
} // namespace
IncomingTaskQueue::IncomingTaskQueue(MessageLoop* message_loop)
: high_res_task_count_(0),
message_loop_(message_loop),
next_sequence_num_(0),
message_loop_scheduled_(false),
always_schedule_work_(AlwaysNotifyPump(message_loop_->type())),
is_ready_for_scheduling_(false) {
}
bool IncomingTaskQueue::AddToIncomingQueue(
const tracked_objects::Location& from_here,
OnceClosure task,
TimeDelta delay,
bool nestable) {
DCHECK(task);
DLOG_IF(WARNING,
delay.InSeconds() > kTaskDelayWarningThresholdInSeconds)
<< "Requesting super-long task delay period of " << delay.InSeconds()
<< " seconds from here: " << from_here.ToString();
PendingTask pending_task(from_here, std::move(task),
CalculateDelayedRuntime(delay), nestable);
#if defined(OS_WIN)
// We consider the task needs a high resolution timer if the delay is
// more than 0 and less than 32ms. This caps the relative error to
// less than 50% : a 33ms wait can wake at 48ms since the default
// resolution on Windows is between 10 and 15ms.
if (delay > TimeDelta() &&
delay.InMilliseconds() < (2 * Time::kMinLowResolutionThresholdMs)) {
pending_task.is_high_res = true;
}
#endif
return PostPendingTask(&pending_task);
}
bool IncomingTaskQueue::HasHighResolutionTasks() {
AutoLock lock(incoming_queue_lock_);
return high_res_task_count_ > 0;
}
bool IncomingTaskQueue::IsIdleForTesting() {
AutoLock lock(incoming_queue_lock_);
return incoming_queue_.empty();
}
int IncomingTaskQueue::ReloadWorkQueue(TaskQueue* work_queue) {
// Make sure no tasks are lost.
DCHECK(work_queue->empty());
// Acquire all we can from the inter-thread queue with one lock acquisition.
AutoLock lock(incoming_queue_lock_);
if (incoming_queue_.empty()) {
// If the loop attempts to reload but there are no tasks in the incoming
// queue, that means it will go to sleep waiting for more work. If the
// incoming queue becomes nonempty we need to schedule it again.
message_loop_scheduled_ = false;
} else {
incoming_queue_.swap(*work_queue);
}
// Reset the count of high resolution tasks since our queue is now empty.
int high_res_tasks = high_res_task_count_;
high_res_task_count_ = 0;
return high_res_tasks;
}
void IncomingTaskQueue::WillDestroyCurrentMessageLoop() {
base::subtle::AutoWriteLock lock(message_loop_lock_);
message_loop_ = NULL;
}
void IncomingTaskQueue::StartScheduling() {
bool schedule_work;
{
AutoLock lock(incoming_queue_lock_);
DCHECK(!is_ready_for_scheduling_);
DCHECK(!message_loop_scheduled_);
is_ready_for_scheduling_ = true;
schedule_work = !incoming_queue_.empty();
}
if (schedule_work) {
DCHECK(message_loop_);
// Don't need to lock |message_loop_lock_| here because this function is
// called by MessageLoop on its thread.
message_loop_->ScheduleWork();
}
}
IncomingTaskQueue::~IncomingTaskQueue() {
// Verify that WillDestroyCurrentMessageLoop() has been called.
DCHECK(!message_loop_);
}
bool IncomingTaskQueue::PostPendingTask(PendingTask* pending_task) {
// Warning: Don't try to short-circuit, and handle this thread's tasks more
// directly, as it could starve handling of foreign threads. Put every task
// into this queue.
// Ensures |message_loop_| isn't destroyed while running.
base::subtle::AutoReadLock hold_message_loop(message_loop_lock_);
if (!message_loop_) {
pending_task->task.Reset();
return false;
}
bool schedule_work = false;
{
AutoLock hold(incoming_queue_lock_);
#if defined(OS_WIN)
if (pending_task->is_high_res)
++high_res_task_count_;
#endif
// Initialize the sequence number. The sequence number is used for delayed
// tasks (to facilitate FIFO sorting when two tasks have the same
// delayed_run_time value) and for identifying the task in about:tracing.
pending_task->sequence_num = next_sequence_num_++;
message_loop_->task_annotator()->DidQueueTask("MessageLoop::PostTask",
*pending_task);
bool was_empty = incoming_queue_.empty();
incoming_queue_.push(std::move(*pending_task));
if (is_ready_for_scheduling_ &&
(always_schedule_work_ || (!message_loop_scheduled_ && was_empty))) {
schedule_work = true;
// After we've scheduled the message loop, we do not need to do so again
// until we know it has processed all of the work in our queue and is
// waiting for more work again. The message loop will always attempt to
// reload from the incoming queue before waiting again so we clear this
// flag in ReloadWorkQueue().
message_loop_scheduled_ = true;
}
}
// Wake up the message loop and schedule work. This is done outside
// |incoming_queue_lock_| because signaling the message loop may cause this
// thread to be switched. If |incoming_queue_lock_| is held, any other thread
// that wants to post a task will be blocked until this thread switches back
// in and releases |incoming_queue_lock_|.
if (schedule_work)
message_loop_->ScheduleWork();
return true;
}
} // namespace internal
} // namespace base
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