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From: Robert Watson <rwatson@FreeBSD.org>
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To: Mikhail Teterin <mi+mill@aldan.algebra.com>
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Cc: Kris Kennaway <kris@FreeBSD.org>, questions@FreeBSD.org,
	Jeremy Chadwick <koitsu@FreeBSD.org>, stable@FreeBSD.org
Subject: Re: "sleeping without queue" ?
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On Tue, 22 Jul 2008, Mikhail Teterin wrote:

> Kris Kennaway ???????(??):
>> Mikhail Teterin wrote:
>>> Kris Kennaway ???????(??):
>>>> Well, I mean kernel backtrace.
>>> Can I obtain that remotely and without restarting/panicking the box? 
>>> Thanks,
>> kgdb on /dev/mem or procstat
>   root@aldan:~ (107) kgdb /boot/kernel/kernel /dev/mem
>   [...]
>   (kgdb) bt
>   #0  0x0000000000000000 in ?? ()
>   Error accessing memory address 0x0: Bad address.
>
> Even less luck with procstat:
>
>   root@aldan:~ (108) locate procstat
>   root@aldan:~ (109) procstat
>   procstat: ???????? ???????.
>   root@aldan:~ (110) man procstat
>   No manual entry for procstat
>
> I'm sorry, but you'll need to be more specific. What should I type? Thanks,

Assuming you're using 7.0 or an older 7-STABLE: procstat(1) appeared after 7.0 
was released, but should be there if you slide forward on 7-STABLE.  You can 
use "procstat -k pid" to see kernel stack traces for kernel threads working on 
behalf of the process.  Depending on the level of detail you require, you can 
use -kk to also list function offsets inside the kernel, but the results are a 
bit harder to read.

Robert N M Watson
Computer Laboratory
University of Cambridge