Re: Apache Children Stuck on futex

On 29/10/11 22:43, Torsten Förtsch wrote:
> On Wednesday, 26 October 2011 05:56:49 Max Barry wrote:
>> $ strace -p 24133
>> Process 24133 attached - interrupt to quit
>> read(5, "!", 1)                         = 1
>> tgkill(24133, 24164, SIGHUP)            = 0
>> tgkill(24133, 24164, SIG_0)             = 0
>> --- SIGTERM (Terminated) @ 0 (0) ---
>> rt_sigreturn(0xf)                       = 0
>> select(0, NULL, NULL, NULL, {0, 500000}) = 0 (Timeout)
>> tgkill(24133, 24140, SIGUSR1)           = 0
>> futex(0x7f9904f4e9d0, FUTEX_WAIT, 24140, NULL
> 
> It would be interesting to see which futex it is blocked on. One way to 
> check that is perhaps to allow core dumps in the apache config and then 
> to send a core dump signal like SEGV, BUS or similar when the process 
> hangs. Use the dump file then to get a stack trace.
> 
> Torsten Förtsch

Thank you very much for the reply! Here is the result:

http://pastebin.com/YDbmq84w

This shows me:
* running the Apache benchmarking utility to generate lots of requests
* identifying a process hung in 'futex_wait' (11447)
* killing it with SEGV
* obtaining a stack trace

Max.