Re: [Xenomai-help] POSIX skin default stacksize

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Steve Deiters wrote:
> I'm trying to determine the source of a bogus initial stack size after I
> initialize a pthread_attr_t with pthread_attr_init.  I'm using the POSIX
> skin (obviously), but I'm not quite sure if it is getting this parameter
> from Xenomai or libc.
> 
> I'm running on a custom PowerPC board with a version 2.6.24.6 kernel.  I
> get the same result using both Xenomai 2.4.10, and 2.5.0.  I noticed the
> issue after having a small program with a few number of threads that was
> crashing the system with an out of memory exception.
> 
> I have a very basic program ...
> 
> ----------------------main.c--------------------------
> #include <stdio.h>
> #include <pthread.h>
> #include <limits.h>
> 
> int main(int argc, char **argv)
> {
>    size_t s;
>    pthread_attr_t a;
> 
>    pthread_attr_init(&a);
>    pthread_attr_getstacksize(&a, &s);
> 
>    printf("PTHREAD_STACK_MIN is %d\n", PTHREAD_STACK_MIN);
>    printf("Default stack size is %d\n", s);
> 
>    return 0;
> }
> -----------------------------------------------------
> 
> For which the output is
> 
>> PTHREAD_STACK_MIN is 16384
>> Default stack size is 8388608
> 
> As you can see, the stack size after I call pthread_attr_init is a
> whopping 8 MB.
> 
> From what I can tell, it is linking against the correct library.  I can
> see the Xenomai options to the linker, with the -lpthread_rt and all
> that.
> 
> Any idea why this would occur?

We do not wrap calls to pthread_attr_init, pthread_attr_setstacksize.
What you see are glibc default for your platform. If you want a
different size, use pthread_attr_setstacksize. Glibc default are made
for general purpose application running on multi-gigas memory x86 boxes.
For other applications, you end up in endless calls to the heavy-weith
pthread interface, pthread_attr_init, pthread_attr_setstacksize,
pthread_attr_setinheritsched, pthread_attr_setschedpolicy,
pthread_attr_setschedparam, pthread_mutexatttr_init,
pthread_mutexattr_setprotocol, pthread_mutexattr_settype, etc...


> 
> Thanks
> 
> 
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-- 
					    Gilles.