Re: [Xenomai-help] How to use Xenomai libraries with "normal" (non Xenomai) linux processes ?

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

roderik.wildenburg@domain.hid wrote:
>>> Please correct me if I am wrong: In your replacement 
>>> pthread_getschedparam would read scheduling parameters which
>>> should have been set with sched_setscheduler before(!) your
>> replacement gets
>>> active. Is this possible at all ? Wouldn´t I have to call 
>>> sched_setscheduler (in "sysup") before I fork? And if calling
>>> after the fork it realy would be racy. So this isn´t a very
>>> feasible solution, isn´t it? Changing the scheduling paramters of
>>> a running Xenoami task probably isn´t possible (probably there is
>>> nothing to recognize the change ?)?
>> You are just repeating what I said. So, I have not much more to
>> say.
>> 
> 
> Yes, but with my own words, so you can tell me whether I understood
> you or not ;-).

Yes you understood.

> 
>>> Linux and Linux is the lowest priority task in Xenomai. So, as
>>> soon as a task is in secondary mode every(!) Xenomai primary mode
>>> task would be scheduled in front of a secondary mode task, I
>>> thought. So, if your statement is right, I can´t see the
>>> difference between primary and secondary mode any more as a
>>> higher prioritized task obviously allways(!?) runs in front of a
>>> lower prioritized one independend whether it runs in primary or
>>> secondary mode? Is there some documenation I could read for
>>> better understanding ? Is this behaviour connected to the Xenomai
>>> "priority coupling" option?
>> Yes, it is what priority coupling means. But it really is the most
>> sane behaviour: you choose a priority and both Linux and Xenomai
>> schedulers cooperate to enfore this priority.
> 
> How are Linux tasks treated which are not linked with any Xenomay
> library, but whose scheduling is set to SCHED_FIFO and whose priority
> is set to some value higher than a Xenomai tasks (with
> sched_setscheduler). When do they run ?

They can prevent a Xenomai task running in secondary mode from running,
but not a Xenomai task running in primary mode.

-- 
                                                 Gilles.