Re: [Xenomai] Hilscher driver for cifX boards

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2013-03-15 14:04, Jerome Poncin wrote:
> Hello Jan,
> 
> Yes you're right. I have 1 thread for test (main) application and the
> driver create one or two thread if IRQ or polling is enable.
> The driver thread are loop waiting event with delay.
> At Driver start it take few second to download firmware and configuration.
> My question is why it's a problem to have a real time that that run few
> second.
> If this task have the bigger priority, it's normal to not release hand
> and to not sleep, I'm right or not ?

Linux is not capable (yet) of handling the case that an online CPU is
100% occupied. Sooner or later, the whole (Linux) system will lock up,
also the timekeeping can be negatively affected. That's nothing Xenomai
can change.

Therefore, every real-time task has to behave properly, sleep on
asynchronous external events or suspend itself for a certain while when
there is nothing to do. In good real-time designs, that is usually no
problem, specifically if the number of tasks is moderate and the
workload is clear. I've seen less obvious problems in large
applications, but those were typically bugs as well.

Jan

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