Date: Mon, 30 May 2005 20:37:51 +0200 (METDST)
From: Esben Nielsen <simlo@phys.au.dk>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: kus Kusche Klaus <kus@keba.com>, James Bruce <bruce@andrew.cmu.edu>,
       "Bill Huey (hui)" <bhuey@lnxw.com>, Andi Kleen <ak@muc.de>,
       Sven-Thorsten Dietrich <sdietrich@mvista.com>,
       Ingo Molnar <mingo@elte.hu>, dwalker@mvista.com, hch@infradead.org,
       akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: RT patch acceptance
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Message-Id: <Pine.OSF.4.05.10505301934001.31148-100000@da410.phys.au.dk>
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On Mon, 30 May 2005, Nick Piggin wrote:

> Esben Nielsen wrote:
> 
> > I do like the idea of guest kernels - especially the ability to enforce a
> > strict seperation of RT and non-RT. But you can't use _any_ part of the
> > Linux kernel in your RT application - not even drivers. I know a lot of
> 
> If you can't use the drivers, then presumably they're no good
> to be used as they are for realtime in Linux either, though :(
>
The driver is probably good enough but because you have to call into the
Linux kernel to use them. With a guest kernel setup  you can forget about
realtime then. With PREEMPT_RT you get hard realtime behaviour out of the
box.

Ofcourse, there is a lot of buts to that. You have to check that the
driver doesn't take a call path which is nontermnistic in special cases
and the path between your application and the driver is deterministic.
A static code checker would be nice...

Esben

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