Apache-worker stuck at 100% CPU

Alfred Perlstein alfred at freebsd.org
Fri Sep 12 22:52:52 UTC 2008

* Ivan Voras <ivoras at freebsd.org> [080912 14:45] wrote:
> 2008/9/12 Alfred Perlstein <alfred at freebsd.org>:
> > Try using "pstack" a few times.  It's in ports.
> >
> > Also, gcore(1) might help.
> Will try.
> > You can also try to attach using gdb.
> I did, but either I'm missing something or I'm not using it well,
> because I can't get a backtrace. How do I select threads to backtrace?
> How do I pick what thread to backtrace?
i think the command is 'info threads' or 'show
threads' then i think you just type 
'thread FOO' to select the thread.

> > 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?
> Yes, it's multithreaded apache. This did help somewhat - when I do it
> I see that it's not actually stuck in umtxn - there's one thread that
> consumes the CPU and it's apparently always running (in state CPUx).
>  7212 www      103    0 30340K  7932K CPU2   2 444:23 99.02% httpd
> I'm currently upgrading the system to 7-STABLE, to see if it helps.

yeah its stuck in userspace doing something..

- Alfred Perlstein

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