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Dominique Goncalves wrote:
> Hi,
>
> I run FreeBSD 7.1-PRERELEASE and with a Perl GTK2 application, Perl
> hang in umtxn state:
>
> PID USERNAME THR PRI NICE SIZE RES STATE TIME WCPU COMMAND
> 76288 dom 1 53 0 67860K 46080K umtxn 0:02 0.00% perl5.8.8
>
> And the only way to stop the application is kill -9
>
> I tried to use ktrace/kdump and ktrace.out show "_umtx_op"
>
> $ kdump -f ktrace.out
> [...]
> 13199 perl5.8.8 RET lstat 0
> 13199 perl5.8.8 CALL gettimeofday(0xbfbfb144,0)
> 13199 perl5.8.8 RET gettimeofday 0
> 13199 perl5.8.8 CALL _umtx_op(0xbfbfd18c,0x3,0x1,0,0)
> 13199 perl5.8.8 RET _umtx_op 0
> 13199 perl5.8.8 CALL sigprocmask(SIG_BLOCK,0xbfbfd120,0x8121490)
> 13199 perl5.8.8 RET sigprocmask 0
> 13199 perl5.8.8 CALL _umtx_op(0x287fb8a0,0x5,0,0,0)
> 13199 perl5.8.8 RET _umtx_op RESTART
> 13199 perl5.8.8 PSIG SIGKILL SIG_DFL
>
>
> How to debug this hang? (btw I'm not a developer)

You can try rebuilding perl with debugging information. I am not sure
this is the best way but I have used this in my /etc/make.conf:

# Disable binaries stripping.
STRIP=
# Add debugging info to binaries.
CFLAGS?=
CFLAGS+= -g3 -ggdb
CXXFLAGS?=
CXXFLAGS+= -g3 -ggdb

When you have that, try running your test case again. When it blocks
again, attach GDB to the hung process: gdb -p PID `which perl`. And then
obtain the call stack: (gdb) bt.

I suspect there will be some pthreads call on top of the stack. I am not
FreeBSD developer but this seems really similar to situations reported
in thread "umtxn and Apache 2.2" and mine "Process in "uwait" state".

>
> $ uname -a
> FreeBSD freebsd7 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #15 r184123:
> Tue Oct 21 16:24:59 CEST 2008
> root@freebsd7:/usr/obj/usr/src/sys/GENERIC i386
>
> Thanks for your help,
> Regards.
>


- --
VH
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