On Wed, Jan 14, 2009 at 3:38 PM, Thorsten Mühlfelder <[email protected]>wrote:
> So I need a damon, too? I thought it's a kernel only thing because there is > extra hardware for this task. > dmesg gives me: > sc520_wdt: WDT driver for SC520 initialised. timeout=30 sec (nowayout=0) > > > On Wed, 14 Jan 2009 15:29:40 -0500 > "Michael Proto" <[email protected]> wrote: > > > On Wed, Jan 14, 2009 at 3:10 PM, Thorsten Mühlfelder <[email protected] > >wrote: > > > > > Hi > > > As far as I know the net4501 watchdog should reboot the machine when > the > > > kernel hangs. How can I test this with Linux? > > > _______________________________________________ > > > Soekris-tech mailing list > > > [email protected] > > > http://lists.soekris.com/mailman/listinfo/soekris-tech > > > > > > > > > > > I can't speak for the linux version as I run FreeBSD on my ALIX and > Net4501 > > boards, but I can kill -9 my watchdogd process and the box will reboot > > within about 15 seconds. I suspect a similar test could be performed > under > > Linux. > > > > > > -Proto > 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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