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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 "base/debug/trace_event.h"
#include "base/location.h"
#include "base/message_loop/message_loop.h"
#include "base/synchronization/waitable_event.h"
namespace base {
namespace internal {
IncomingTaskQueue::IncomingTaskQueue(MessageLoop* message_loop)
: message_loop_(message_loop),
next_sequence_num_(0) {
}
bool IncomingTaskQueue::AddToIncomingQueue(
const tracked_objects::Location& from_here,
const Closure& task,
TimeDelta delay,
bool nestable) {
AutoLock locked(incoming_queue_lock_);
PendingTask pending_task(
from_here, task, CalculateDelayedRuntime(delay), nestable);
return PostPendingTask(&pending_task);
}
bool IncomingTaskQueue::TryAddToIncomingQueue(
const tracked_objects::Location& from_here,
const Closure& task) {
if (!incoming_queue_lock_.Try()) {
// Reset |task|.
Closure local_task = task;
return false;
}
AutoLock locked(incoming_queue_lock_, AutoLock::AlreadyAcquired());
PendingTask pending_task(
from_here, task, CalculateDelayedRuntime(TimeDelta()), true);
return PostPendingTask(&pending_task);
}
bool IncomingTaskQueue::IsHighResolutionTimerEnabledForTesting() {
#if defined(OS_WIN)
return !high_resolution_timer_expiration_.is_null();
#else
return true;
#endif
}
bool IncomingTaskQueue::IsIdleForTesting() {
AutoLock lock(incoming_queue_lock_);
return incoming_queue_.empty();
}
void IncomingTaskQueue::LockWaitUnLockForTesting(WaitableEvent* caller_wait,
WaitableEvent* caller_signal) {
AutoLock lock(incoming_queue_lock_);
caller_wait->Signal();
caller_signal->Wait();
}
void 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())
incoming_queue_.Swap(work_queue); // Constant time
DCHECK(incoming_queue_.empty());
}
void IncomingTaskQueue::WillDestroyCurrentMessageLoop() {
#if defined(OS_WIN)
// If we left the high-resolution timer activated, deactivate it now.
// Doing this is not-critical, it is mainly to make sure we track
// the high resolution timer activations properly in our unit tests.
if (!high_resolution_timer_expiration_.is_null()) {
Time::ActivateHighResolutionTimer(false);
high_resolution_timer_expiration_ = TimeTicks();
}
#endif
AutoLock lock(incoming_queue_lock_);
message_loop_ = NULL;
}
IncomingTaskQueue::~IncomingTaskQueue() {
// Verify that WillDestroyCurrentMessageLoop() has been called.
DCHECK(!message_loop_);
}
TimeTicks IncomingTaskQueue::CalculateDelayedRuntime(TimeDelta delay) {
TimeTicks delayed_run_time;
if (delay > TimeDelta()) {
delayed_run_time = TimeTicks::Now() + delay;
#if defined(OS_WIN)
if (high_resolution_timer_expiration_.is_null()) {
// Windows timers are granular to 15.6ms. If we only set high-res
// timers for those under 15.6ms, then a 18ms timer ticks at ~32ms,
// which as a percentage is pretty inaccurate. So enable high
// res timers for any timer which is within 2x of the granularity.
// This is a tradeoff between accuracy and power management.
bool needs_high_res_timers = delay.InMilliseconds() <
(2 * Time::kMinLowResolutionThresholdMs);
if (needs_high_res_timers) {
if (Time::ActivateHighResolutionTimer(true)) {
high_resolution_timer_expiration_ = TimeTicks::Now() +
TimeDelta::FromMilliseconds(
MessageLoop::kHighResolutionTimerModeLeaseTimeMs);
}
}
}
#endif
} else {
DCHECK_EQ(delay.InMilliseconds(), 0) << "delay should not be negative";
}
#if defined(OS_WIN)
if (!high_resolution_timer_expiration_.is_null()) {
if (TimeTicks::Now() > high_resolution_timer_expiration_) {
Time::ActivateHighResolutionTimer(false);
high_resolution_timer_expiration_ = TimeTicks();
}
}
#endif
return delayed_run_time;
}
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.
// This should only be called while the lock is taken.
incoming_queue_lock_.AssertAcquired();
if (!message_loop_) {
pending_task->task.Reset();
return false;
}
// Initialize the sequence number. The sequence number is used for delayed
// tasks (to faciliate 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_++;
TRACE_EVENT_FLOW_BEGIN0("task", "MessageLoop::PostTask",
TRACE_ID_MANGLE(message_loop_->GetTaskTraceID(*pending_task)));
bool was_empty = incoming_queue_.empty();
incoming_queue_.push(*pending_task);
pending_task->task.Reset();
// Wake up the pump.
message_loop_->ScheduleWork(was_empty);
return true;
}
} // namespace internal
} // namespace base
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