Apache-worker stuck at 100% CPU

[Ivan Voras]

2008/9/13 Alfred Perlstein <alfred at freebsd.org>:

>> Yes, it's multithreaded apache. This did help somewhat - when I show threads in top
>> 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).
>>
>>   PID USERNAME PRI NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
>>  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.

It didn't help. Exactly the same symptom happened again. It looks like
it happens a few days after the last system reboot. After it happens
the first time, restarting Apache immediately produces one such
"stuck" thread - it looks like some system state gets corrupted over
time.

>> How do I pick what thread to backtrace in gdb?
>
> i think the command is 'info threads' or 'show
> threads' then i think you just type
> 'thread FOO' to select the thread.

Both commands don't work / don't exist. Any others?

(background: apache22-worker port, no mod_php, on 7.0 and 7-STABLE
suddenly gets stuck at 100% CPU; the same setup worked on 6-STABLE.
I'm looking for ideas)