Subject: Re: watchdog timer
To: Simon Burge <>
From: Andrew Brown <>
List: netbsd-users
Date: 04/06/2003 21:32:58
>> Is there some built-in software watchdog timer?  wdogctl(8) on 1.6
>> implies that there is; running wdogctl says that nothing is configured.
>> A quick grep didn't turn anything up, but it's a fairly obvious feature
>> to want -- am I missing something?  (Or is that a hint that I should
>> write such a driver?)
>The wdogctl interface is meant for hardware watchdog timers.  This is
>what wdogctl reports on a IBM PowerPC 405GP box:
>	walnut# wdogctl
>	Available watchdog timers:
>		wdog0, 5 second period

fwiw, the weasel card also provides a hardware watchdog to the
operating system.

>Setting the timer and disabling the tickle results in the CPU itself
>doing a hardware reset after the specified time.
>I'm not sure how you'd define a software watchdog timer (since by
>definition if the software is hosed it wont be able to tickle the
>software timer(!)), unless you mean you want something for userland

a watchdog implemented completely in software might be useful for
those situations where something wedges the top half of the kernel,
but he bottom half still runs.  ie, you can ping the machine, and
telnet to open tcp ports (or get resets from the closed ones), but the
userland application that's accepting the connections never runs

|-----< "CODE WARRIOR" >-----|             * "ah!  i see you have the internet (Andrew Brown)                that goes *ping*!"       * "information is power -- share the wealth."