watchdog
The Linux software watchdog is a timer that continuously counts down from a specified start value. Once it reaches zero a function named “watchdog_fire” is called that logs the event and initiates a hard reset. A watchdog daemon is therefore needed to refresh the timer. As long as the daemon is present the timer will never fire, but if the daemon stops working for some reason, the timer will fire and reboot the machine. However, with no additional hardware, the watchdog is not able to recover from every possible hang up. For instance, if the interrupt system itself hangs up, the software watchdog is no cure at all.
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