Re: [Xenomai-help] Maximum number of realtime tasks

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

Daniel Schnell wrote:
> Gilles Chanteperdrix wrote:
> 
> 
>>Setting the stack size with pthread_attr_setstacksize seems to allow
>>a stack greater than the limit fixed by ulimit, but I do not think it
>>is wise to rely on such a behaviour.  
> 
> 
> If one wants to have always the same stack size for every thread than
> ulimit -s would be probably the way to go. But often in Realtime
> applications it is the preferred way of setting  the stack size
> individually, so one doesn't waste too much memory. A mixture of both
> seems to be tempting: setting a general stack size and individually
> change it. So why not rely on this ? Which part in the system actually
> creates the stack for a Xenomai task and how is the interaction between
> Linux and Xenomai to derive the general system wide stack limit to a
> Xenomai task ?

The way I understand ulimit (or the setrlimit syscall), it should be
used to set a maximum limit, so the fact that pthread_attr_setstacksize
allow to bypass this limit may be a bug that may be corrected one day.
So, I repeat, I would not rely on this behaviour.

> 
> Is there a way to find out, which thread has which stack size ?

Each thread stack is set up as a mapping in /proc/pid/maps, so if you
know one address on each stack, you may find out which thread has
which stack. Ok, it is not easy, but I know no other way.

-- 
                                                  Gilles Chanteperdrix