CONFIG_PREEMPT_RT in real-world applications

[Sven Geggus]

Hello embedded-linux folks,

I am kind of confuded how a piece of realtime code would look like using
Ingo Molnars CONFIG_PREEMPT_RT patch.

What would I need to make a process realtime. How would I be able to
generate a somewhat exact timing, e.g. for a control circuit. From the
perspective of a normal Linux system programming guy /dev/rtc comes
to mind.

For the realtime stuff, would it be enough to just use a negative nice-level
and a SCHED_FIFO policy?

Is there any kind of realtime programming Howto which I have not found
searching the web? Or is this just an exmple of another piece of fine but
undocumented work which is quite common in the Open-Source world?

Sven

--
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/me is giggls@ircnet, http://sven.gegg.us/ on the Web

[Mile Blenton]

Sven Geggus wrote:

>
> Is there any kind of realtime programming Howto which I have not found
> searching the web? Or is this just an exmple of another piece of fine but
> undocumented work which is quite common in the Open-Source world?
>

take a look at www.rtai.org

regards,
Mario

[Sven Geggus]

Mile Blenton <nomejl@blentronix.com> wrote:

> take a look at www.rtai.org

RTAI is not what I am talking about. Its Ingo Molnars patches for the
Standard Kernel aka Realtime preemtion.

Sven

--
"Das ist halt der Unterschied: Unix ist ein Betriebssystem mit Tradition,
die anderen sind einfach von sich aus unlogisch."
(Anselm Lingnau in de.comp.os.unix.discussion)
/me ist giggls@ircnet, http://sven.gegg.us/ im WWW

[Alain Mosnier]

Hi Sven,

I don't have an answer, but:
- I guess you have read this: http://lkml.org/lkml/2005/6/7/256. If not,
the information is probably relevant to your question.
- The guys involved in that discussion should be able to answer you
(Ingo himself?).
- Maybe it's a question that can be posted on the kernel mailing list
itself (not sure about that, I haven't used it before, but I would guess
that not many embedded developpers have done what you are trying to do).
- I guess you also already know this article:
http://linuxdevices.com/articles/AT3479098230.html, but just in case...

Was just trying to help a little, since you haven't received any
relevant answer after nearly two days.

Good luck,

Regards,

Alain

[Sven Geggus]

Alain Mosnier <alain.mosnier@chello.se> wrote:

> - I guess you also already know this article:
> http://linuxdevices.com/articles/AT3479098230.html, but just in case...

I did not know it, but unfortunately it does not talk about
CONFIG_PREEMPT_RT anyway.

Sven

--
"The American news-media is no longer a news source; it is a
cheerleading squad." (unknown source)

/me is giggls@ircnet, http://sven.gegg.us/ on the Web