Subj : Re: pthread_create hangs
To   : comp.programming.threads
From : gg
Date : Wed Apr 13 2005 11:52 am

gg wrote:

> Hi,
> 
> I'm developping a multi-thread application on debian sarge, kernel 2.4.28.
> When I do heavy-load tests, pthread_create sometimes hangs and
> __pthread_manager thread takes all CPU (R status) :
> top :
>    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>   6909 vocal     16   0 17404  16m  15m R 18.4  3.4   0:53.32 cvfmon
> 
> __pthread_manager thread :
> (gdb) bt
> #0  0x4054385a in poll () from /lib/libc.so.6
> #1  0x40429b50 in __pthread_manager () from /lib/libpthread.so.0
> #2  0x4054c69a in clone () from /lib/libc.so.6
> 
> pthread_create thread :
> 
> #0  0x4042c604 in __pthread_sigsuspend () from /lib/libpthread.so.0
> #1  0x4042c3c8 in __pthread_wait_for_restart_signal () from
> /lib/libpthread.so.0
> #2  0x4042bc42 in pthread_create@@GLIBC_2.1 () from /lib/libpthread.so.0
> #3  0x0805abb2 in cvfmon_pthread_create (id=0x80959f0, bool_joinable=1,
> init=0xfffffffc, arg=0xfffffffc, fct_appelante=0x808746c "babySitter")
> at commun.c:1653
> #4  0x08061540 in babySitter () at canal.c:2490
> #5  0x40429e51 in pthread_start_thread () from /lib/libpthread.so.0
> #6  0x4054c69a in clone () from /lib/libc.so.6
> 
> I haven't been able to make simpler test programs that reproduce this
> problem.
> Any idea?
> 
> Thanx in advance.
> 
> Regards,

Hi,


I had a look at __pthread_manager code, it seems to be a loop, that calls
the poll function on a pipe (__pthread_manager_reader file descripteur) in
order to wait for pthread_create request. 

A problem with the pipe could be the origin of my "pthread_create hangs" and
"R status for __pthread_manager" problems. 

If the pipe is out of order, the poll function call fails, the request can't
be read from the pipe, and the pthread_manager thread loops without
sleeping.

What can be the problem with the pipe?
What do you think about this hypothesis?

Thanks in advance,
Regards,

.