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// Copyright (c) 2010 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/threading/watchdog.h"
#include "base/compiler_specific.h"
#include "base/logging.h"
#include "base/threading/platform_thread.h"
namespace base {
// Start thread running in a Disarmed state.
Watchdog::Watchdog(const TimeDelta& duration,
const std::string& thread_watched_name,
bool enabled)
: init_successful_(false),
lock_(),
condition_variable_(&lock_),
state_(DISARMED),
duration_(duration),
thread_watched_name_(thread_watched_name),
ALLOW_THIS_IN_INITIALIZER_LIST(delegate_(this)) {
if (!enabled)
return; // Don't start thread, or doing anything really.
init_successful_ = PlatformThread::Create(0, // Default stack size.
&delegate_,
&handle_);
DCHECK(init_successful_);
}
// Notify watchdog thread, and wait for it to finish up.
Watchdog::~Watchdog() {
if (!init_successful_)
return;
{
AutoLock lock(lock_);
state_ = SHUTDOWN;
}
condition_variable_.Signal();
PlatformThread::Join(handle_);
}
void Watchdog::Arm() {
ArmAtStartTime(TimeTicks::Now());
}
void Watchdog::ArmSomeTimeDeltaAgo(const TimeDelta& time_delta) {
ArmAtStartTime(TimeTicks::Now() - time_delta);
}
// Start clock for watchdog.
void Watchdog::ArmAtStartTime(const TimeTicks start_time) {
{
AutoLock lock(lock_);
start_time_ = start_time;
state_ = ARMED;
}
// Force watchdog to wake up, and go to sleep with the timer ticking with the
// proper duration.
condition_variable_.Signal();
}
// Disable watchdog so that it won't do anything when time expires.
void Watchdog::Disarm() {
AutoLock lock(lock_);
state_ = DISARMED;
// We don't need to signal, as the watchdog will eventually wake up, and it
// will check its state and time, and act accordingly.
}
void Watchdog::Alarm() {
DVLOG(1) << "Watchdog alarmed for " << thread_watched_name_;
}
//------------------------------------------------------------------------------
// Internal private methods that the watchdog thread uses.
void Watchdog::ThreadDelegate::ThreadMain() {
SetThreadName();
TimeDelta remaining_duration;
while (1) {
AutoLock lock(watchdog_->lock_);
while (DISARMED == watchdog_->state_)
watchdog_->condition_variable_.Wait();
if (SHUTDOWN == watchdog_->state_)
return;
DCHECK(ARMED == watchdog_->state_);
remaining_duration = watchdog_->duration_ -
(TimeTicks::Now() - watchdog_->start_time_);
if (remaining_duration.InMilliseconds() > 0) {
// Spurios wake? Timer drifts? Go back to sleep for remaining time.
watchdog_->condition_variable_.TimedWait(remaining_duration);
continue;
}
// We overslept, so this seems like a real alarm.
// Watch out for a user that stopped the debugger on a different alarm!
{
AutoLock static_lock(static_lock_);
if (last_debugged_alarm_time_ > watchdog_->start_time_) {
// False alarm: we started our clock before the debugger break (last
// alarm time).
watchdog_->start_time_ += last_debugged_alarm_delay_;
if (last_debugged_alarm_time_ > watchdog_->start_time_)
// Too many alarms must have taken place.
watchdog_->state_ = DISARMED;
continue;
}
}
watchdog_->state_ = DISARMED; // Only alarm at most once.
TimeTicks last_alarm_time = TimeTicks::Now();
watchdog_->Alarm(); // Set a break point here to debug on alarms.
TimeDelta last_alarm_delay = TimeTicks::Now() - last_alarm_time;
if (last_alarm_delay <= TimeDelta::FromMilliseconds(2))
continue;
// Ignore race of two alarms/breaks going off at roughly the same time.
AutoLock static_lock(static_lock_);
// This was a real debugger break.
last_debugged_alarm_time_ = last_alarm_time;
last_debugged_alarm_delay_ = last_alarm_delay;
}
}
void Watchdog::ThreadDelegate::SetThreadName() const {
std::string name = watchdog_->thread_watched_name_ + " Watchdog";
PlatformThread::SetName(name.c_str());
DVLOG(1) << "Watchdog active: " << name;
}
// static
void Watchdog::ResetStaticData() {
AutoLock lock(static_lock_);
last_debugged_alarm_time_ = TimeTicks();
last_debugged_alarm_delay_ = TimeDelta();
}
// static
Lock Watchdog::static_lock_; // Lock for access of static data...
// static
TimeTicks Watchdog::last_debugged_alarm_time_ = TimeTicks();
// static
TimeDelta Watchdog::last_debugged_alarm_delay_;
} // namespace base
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