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// Copyright 2008, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// The Watchdog class creates a second thread that can Alarm if a specific
// duration of time passes without proper attention. The duration of time is
// specified at construction time. The Watchdog may be used many times by
// simply calling Arm() (to start timing) and Disarm() (to reset the timer).
// The Watchdog is typically used under a debugger, where the stack traces on
// other threads can be examined if/when the Watchdog alarms.
// Some watchdogs will be enabled or disabled via command line switches. To
// facilitate such code, an "enabled" argument for the constuctor can be used
// to permanently disable the watchdog. Disabled watchdogs don't even spawn
// a second thread, and their methods call (Arm() and Disarm()) return very
// quickly.
#ifndef BASE_WATCHDOG_H__
#define BASE_WATCHDOG_H__
#include <string>
#include "base/condition_variable.h"
#include "base/lock.h"
#include "base/time.h"
class Watchdog {
public:
// TODO(JAR)change default arg to required arg after all users have migrated.
// Constructor specifies how long the Watchdog will wait before alarming.
Watchdog(const TimeDelta& duration,
const std::wstring& thread_watched_name,
bool enabled = true);
virtual ~Watchdog();
// Start timing, and alarm when time expires (unless we're disarm()ed.)
void Arm(); // Arm starting now.
void ArmSomeTimeDeltaAgo(const TimeDelta& time_delta);
void ArmAtStartTime(const TimeTicks start_time);
// Reset time, and do not set off the alarm.
void Disarm();
// Alarm is called if the time expires after an Arm() without someone calling
// Disarm(). This method can be overridden to create testable classes.
virtual void Alarm() {
DLOG(INFO) << "Watchdog alarmed for " << thread_watched_name_;
}
private:
enum State {ARMED, DISARMED, SHUTDOWN };
// Windows thread start callback
static DWORD WINAPI ThreadStart(void* pThis);
// Loop and test function for our watchdog thread.
unsigned Run();
void Watchdog::SetThreadName() const;
Lock lock_; // Mutex for state_.
ConditionVariable condition_variable_;
State state_;
const TimeDelta duration_; // How long after start_time_ do we alarm?
const std::wstring thread_watched_name_;
HANDLE handle_; // Handle for watchdog thread.
DWORD thread_id_; // Also for watchdog thread.
TimeTicks start_time_; // Start of epoch, and alarm after duration_.
// When the debugger breaks (when we alarm), all the other alarms that are
// armed will expire (also alarm). To diminish this effect, we track any
// delay due to debugger breaks, and we *try* to adjust the effective start
// time of other alarms to step past the debugging break.
// Without this safety net, any alarm will typically trigger a host of follow
// on alarms from callers that specify old times.
static Lock static_lock_; // Lock for access of static data...
// When did we last alarm and get stuck (for a while) in a debugger?
static TimeTicks last_debugged_alarm_time_;
// How long did we sit on a break in the debugger?
static TimeDelta last_debugged_alarm_delay_;
DISALLOW_EVIL_CONSTRUCTORS(Watchdog);
};
#endif // BASE_WATCHDOG_H__
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