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Date: Fri, 12 Sep 2008 09:58:09 -0700
From: Alfred Perlstein <alfred@freebsd.org>
To: Ivan Voras <ivoras@freebsd.org>
Message-ID: <20080912165808.GE16977@elvis.mu.org>
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Cc: freebsd-threads@freebsd.org
Subject: Re: Apache-worker stuck at 100% CPU
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* Ivan Voras <ivoras@freebsd.org> [080912 04:09] wrote:
> Hi,
> 
> I'm running apache2.2.9-worker without mod_php (with mod_fcgid and PHP
> as FastCGI) and a process or a thread repeatedly gets stuck:
> 
>   PID USERNAME  THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
>  5503 www        41  96    0 50820K 30960K umtxn  0 722:42 99.32% httpd
> 
> It doesn't use sys time and ktrace doesn't record anything.
> 
> Any clues where to dig next?
> 
> I'm not using any unusual modules for apache, and the same configuration
> worked in 6.3 (this system was upgraded from 6.3 to 7.0-R - I checked
> that all apache dependancies are compiled for 7.0).

Try using "pstack" a few times.  It's in ports.

Also, gcore(1) might help.

You can also try to attach using gdb.

Basically, one of these tools should give you a stack trace which
can help.

It's interesting that the process is in "umtxn" though, is it
multithreaded apache?  Can you dump the threads?  I think top(1)
has an option to view each thread, how about trying that?

thank you,
-Alfred