RE: [Xenomai-help] Strange behaviour w/mutex&semaphore

[Philippe Gerum <rpm@xenomai.org>]

On Thu, 2006-07-20 at 13:17 +0200, ROSSIER Daniel wrote:
> 
> > -----Message d'origine-----
> > De : jan.kiszka@domain.hid [mailto:jan.kiszka@domain.hid]
> > Envoyé : jeudi, 20. juillet 2006 13:03
> > À : ROSSIER Daniel
> > Cc : xenomai@xenomai.org
> > Objet : Re: [Xenomai-help] Strange behaviour w/mutex&semaphore
> > 
> > ROSSIER Daniel wrote:
> > > Hi all,
> > >
> > > I've a strange behaviour with the attached piece of code.
> > > It's really simple: there are 3 tasks and we're spinning within the task
> > in order
> > > to simulate task load.
> > >
> > > It's a pure academic exercice, so don't try to think about the
> > usefulness of this code ;-)
> > >
> > >
> > > Actually, after insmod'ing the code into the kernel, the system freezes
> > and
> > > the "meteoDataAcquisition" task is suspended runaway by the internal
> > xenomai watchdog.
> > >
> > > Why?
> > >
> > > Anything wrong in this code?
> > 
> > Check the values you assign to rt_task_set_periodic. Kind of... fast?
> 
> No, with at these frequencies, there is no problem (the jiffy is at 1ms). Actually, putting TM_NOW in the rt_task_set_periodic() instead of 18 as it is, we noticed that it works.
> Removing the mutex & semaphore stuff, with the delay in set_periodic(), does not change the behaviour.
> We came up with this issue after another one, actually, with a more sophisticated code showing a priority inversion. We reduce the code, and then find this issue. I do not know it both issues are related, but I'd like
> to solve this one first.
> 

-  rt_task_set_periodic(&meteoDataAcquisitionTask, 18, 1000);
+  rt_task_set_periodic(&meteoDataAcquisitionTask, rt_timer_read() + 18,
1000);

The current call should return with -ETIMEDOUT, in which case, the
associated acquisition thread would enter a runaway loop, with
rt_task_wait_period() systematically bailing out upon the same error,
which in turn makes the task sucking all the available CPU. Then came
the relentless watchdog...

> > 
> > >
> > > Thanks for any advice.
> > >
> > > Daniel
> > >
> > >
> > >
> > > ------------------------------------------------------------------------
> > >
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> > > Xenomai-help@domain.hid
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> > 
> 
> 
> 
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-- 
Philippe.