Re: [Xenomai-help] RT Task RPC over a POSIX/Native Queue

[Guvenc Gulce <gulceg@domain.hid>]

Gilles Thanks.. I will look into the nomac possibility in rtnet..

And Jan.. your comments here brings me back to my original 
post in this topic where I said:


>I was thinking about a generic library/framework which would allow an Xenomai 
>RT Task call a Linux API 
>function which would be then marshalled over a Posix/Native Queue to another 
>Xenomai RT Task which then 
>would do the dirty job of calling Linux functions.

and when we are at it why not to make a generic thing from 
this low prio proxy RT Task <-> RT Task communicate with each other with IPC 
and low prio RT Task does the dirty job of calling Linux API idea.. such a 
thing may be needed for other Linux APIs and not only for the network part..

I will try to develop this idea and prepare some test code maybe the 
community is also interested to have it in Xenomai tree.. more 
comments are also welcome..

Thanks & Regards

Guvenc 




----- Original Message ----
From: Jan Kiszka <jan.kiszka@domain.hid>
To: Guvenc Gulce <gulceg@domain.hid>
Cc: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>; xenomai@xenomai.org
Sent: Wednesday, September 9, 2009 12:12:29 PM
Subject: Re: RT Task RPC over a POSIX/Native Queue

Guvenc Gulce wrote:
> rt_net is nice but then all network participants have to use rt_net otherwise 
> the realtime communication is not guaranteed on the wire.. in some cases 
> the real-timeliness on the wire may not be needed but the determinism 
> of the rt-task may still be an issue..
> 
> I think it is a great flexibility to give an rt task the chance to communicate 
> with non rt_net clients and servers in the network without worrying about 
> losing its determinism. 

To achieve this, you just need to set up a low-prio Xenomai server task
that accepts to-be-transmitted data from the RT task sends it out,
collects replies and dispatches them back to the sender. You may use
queues or shared memory as IPC mechanisms for the RT<->proxy
communication. They just have to be Xenomai provided. The effect will be
that the proxy is switching back and forth between primary (Xenomai) and
secondary (Linux) mode, but your RT task will stay in primary mode.

As you do not care about determinism of the network communication, you
also do not need RTnet. It would only introduce the risk that non-RT
network participant overload your box. And this load would show up in
the RT domain because RTnet would have to handle it.

Jan

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