Hmm, I guess you're talking about a software based solution. But the the 
Soekris boards have a hardware watchdog, which perhaps works the other way 
round:
Kernel talks with it's driver to the hardware. If the kernel freezes the 
hardware chip resets the machine because it doesn't get "pings" by the kernel 
anymore.

This would be more logical to me, but I really don't know ;-)


On Wed, 14 Jan 2009 18:08:14 -0500
"Michael Proto" <[email protected]> wrote:

> I'm no authority on the subject (I've learned most of what I know simply by
> lurking this list and reading PHK's posts), but there are two pieces to
> watchdog-- the kernel-side piece and a userland daemon that acts as a dead
> man's switch. The userland watchdogd (or whatever linux's equivalent)
> enables the kernel bits and sends a "I'm still running" message to the
> kernel every few seconds. If the kernel doesn't get that message, it assumes
> userland is broken and institutes a reboot. This is why you can test with a
> kill -9 to the watchdogd program-- it doesn't have time to deactivate the
> in-kernel watchdog component before it dies.
> 
> 
> -Proto
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