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From: Robert Watson <rwatson@freebsd.org>
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To: Michael Nottebrock <michaelnottebrock@gmx.net>
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Subject: Re: crashdumps not working
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On Wed, 8 Dec 2004, Robert Watson wrote:

> On Tue, 7 Dec 2004, Michael Nottebrock wrote:
> 
> > I recently enabled SW_WATCHDOG in my kernel, but when watchdog triggers
> > a panic, no crashdump is taken although dumps are enabled. What could be
> > causing this? 
> 
> If you drop to the debugger by using the debug.kdb.enter sysctl, and do
> "call doadump", followed by a reset, does a dump get generated
> successfully?  I.e., are they completely broken on your system, or is
> this somehow a property of the particular hang you're seeing.  (Do the
> above with caution and in a situation where you don't mind fscking,
> needless to say). 

It this is an SMP box, you might also try setting debug.kdb.stop_cpus to
0.  Normally when entering the debugger, the processor entering the
debugger will send an IPI to the other CPUs to stop them in order to
quiesce the system state a bit.  If one or more processors are in a state
where processing the top IPI isn't possible, the procesor entering the
debugger will wait for them to stop ... potentially for a very long time,
and in a tight loop.  Changing the setting to 0 might improve the chances
of getting into the debugger (etc).

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Principal Research Scientist, McAfee Research