How to find the cause of a hang
ltning at anduin.net
Tue Aug 17 22:31:17 PDT 2004
On 14. Aug 2004, at 22:50, Julian Elischer wrote:
> Eirik Øverby wrote:
>> Hi all,
>> I'm currently experiencing frequent (about once per week) hangs of a
>> server that is about 1500 kilometers away from me. I have a serial
>> cable on the box, and using minicom on the neighbor box I am now in
>> the kernel debugger - but I'm at a complete loss as to what to do to
>> figure out what is, in fact, wrong.
>> Calling panic or boot doesn't work - it just stops at "syncing
>> disks..." and never actually reboots. I suspect something fishy going
>> on with disk I/O, but I can't be certain of that.
>> The box responds to ping - until I call panic or boot - but no other
>> services are working.
> try capture a stack trace "tr"
Looks like the box is "idle"
> if you have KTR enabled do "show ktr"
This is 4.x... As my follow-up msg on current@ indicated (yes i posted
to the wrong list initially ;)
> do "ps"
An insane number of cron processes.. Is it trying to run scheduled jobs
and fails because of the hang?
> do show pcpu
> show witness
> show locks
No workie on 4.x...
> if you have a dump device define..
> call doadump
No dump device here (if disk is the problem, it would be of no use I
guess), and i get undefined symbol anyway.
> then to reboot..
> "call cpu_reset"
Now that one is handy. ;)
> The dump will appear after the next boot in /var/crash
> if it's not big enough for a complete ram dump, symlink it to
> somewhere where there is enough room.
> when you have all that.. let us know :-)
I have what I have. See
(it is too long to include in a mail...
Got any clues for me?
>> What can I do? I'm now at the db> prompt ... Help :)
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