Thanks for your response, Gilles.

i modified the code to use semaphore instead of mutex, which worked fine.
Attached is a compilation of some latency figures and system loading figures
(using lmbench)
that i obtained from my proprietary ARM-9 board, using Xenomai-2.5.2.

Any comments are welcome. TIY.


On Sat, Jun 19, 2010 at 1:15 AM, Gilles Chanteperdrix <
gilles.chanteperdrix@xenomai.org> wrote:

> Gilles Chanteperdrix wrote:
> > Nero Fernandez wrote:
> >> On Fri, Jun 18, 2010 at 7:42 PM, Gilles Chanteperdrix
> >> <gilles.chanteperdrix@xenomai.org
> >> <mailto:gilles.chanteperdrix@xenomai.org>> wrote:
> >>
> >>     Nero Fernandez wrote:
> >>     > Hi,
> >>     >
> >>     > Please find an archive attached, containing :
> >>     >  - a program for testing context-switch-latency using posix-APIs
> >>     >    for native linux kernel and xenomai-posix-skin (userspace).
> >>     >  - Makefile to build it using xenomai
> >>
> >>     Your program is very long to tell fast. But it seems you are using
> the
> >>     mutex as if they were recursive. Xenomai posix skin mutexes used to
> be
> >>     recursive by default, but no longer are.
> >>
> >>     Also note that your code does not check the return value of the
> posix
> >>     skin services, which is a really bad idea.
> >>
> >>     --
> >>                                                Gilles.
> >>
> >>
> >> Thanks for the prompt response.
> >>
> >> Could you explain  'recursive usage of mutex' a little further?
> >> Are the xenomai pthread-mutexes very different in behaviour than regular
> >> posix mutexes?
> >
> > The posix specification does not define the default type of a mutex. So,
> >  in short, the behaviour of a "regular posix mutex" is unspecified.
> > However, following the principle of least surprise, Xenomai chose, like
> > Linux, to use the "normal" type by default.
> >
> > What is the type of a posix mutex is explained in many places, starting
> > with Xenomai API documentation. So, no, I will not repeat it here.
>
> Actually, that is not your problem. However, you do not check the return
> value of posix services, which is a bad idea. And indeed, if you check
> it you will find your error: a thread which does not own a mutex tries
> to unlock it.
>
> Sorry, mutex are not semaphore, this is invalid, and Xenomai returns an
> error in such a case.
>
> --
>                                             Gilles.
>