Subj : Re: pthread_create hangs
To   : comp.programming.threads
From : gg
Date : Thu Apr 14 2005 10:38 am

gg wrote:

> 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,

Hi,

I tried to print errno with gdb at after a poll function call :
the value is 4 == EINTR : interrupted system call.
Any idea?

Thanks in advance,
Regards,

.