debugging frequent kernel panics on 8.2-RELEASE

Andriy Gapon avg at
Mon Aug 15 12:00:06 UTC 2011

on 15/08/2011 13:34 Steven Hartland said the following:
> ----- Original Message ----- From: "Andriy Gapon" <avg at>
>> I think (not 100% sure) that with DDB in kernel we could get a better backtrace
>> here, possibly with pre-dblfault stack frames, because DDB backend is a bit more
>> smarter than the trivial stack(9) printer.
> I've added this into the the kernel on my test machine and will try
> to get it panic over the next few days. Seems to need a few days on
> uptime before the panics start happening. In addition to increasing
> KSTACK_PAGES to 12, if you believe this may be stack exhaustion, do
> you want me to remove this increase?

Yes, I think it would make sense to change KSTACK_PAGES to the default value.
But, OTOH, if you can afford to have DDB in a few more machines, then it would be
interesting to compare behavior with different stack sizes.

BTW, if you don't want your machines to sit at ddb prompt after panic, then you'd
also need either KDB_UNATTENDED option or set debug.debugger_on_panic=0.

Andriy Gapon

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