Re: [PATCH] [request for inclusion] Realtime LSM

Nick Piggin
2005-01-14T03:33:36Z

On Fri, 2005-01-14 at 14:18 +1100, Con Kolivas wrote:
> Andrew Morton wrote:
> > Paul Davis <paul@linuxaudiosystems.com> wrote:
> >
> >>>SCHED_FIFO and SCHED_RR are definitely privileged operations and you
> >>
> >>this is the crux of what this whole debate is about. for all of you
> >>people who think about linux on multi-user systems with network
> >>connectivity, running servers and so forth, this is clearly a given.
> >>
> >>but there is large and growing body of machines that run linux where
> >>the sole human user of the machine has a strong and overwhelming
> >>desire to have tasks run with the characteristics offered by
> >>SCHED_FIFO and/or SCHED_RR. are they still "privileged" operations on
> >>this class of linux system? what about linux installed on an embedded
> >>system, with a small LCD screen and the sole purpose of running audio
> >>apps live? are they still privileged then?
> >>
> >
> >
> > Paul. Everyone agrees with you. I think. We just need to work out
> > the best way of doing it.
> >
> > Would I be right in suspecting that we know what to do, but nobody has
> > stepped up to write the code? It's kinda looking like that?
>
> I thought I made it clear i had already volunteered. I was after a
> response to my proposal for how to do it.
>

It sounds to me like both your proposals may be too complex and not
sufficiently deterministic (I don't know for sure, maybe that's
exactly what the RT people want).

I wouldn't have thought it is so much a matter of having real-time-ish
scheduling available that tries to play nicely in a multi user machine.
That must still imply that either the user is able to unduly tie up
resources (and thus it has to be a privileged operation), or that it
sometimes can't meet its "guarantees" (in which case, is it useful?).

I was thinking that the solution might be more along the lines of
a nice way to handle privileges for these guys.

I could be completely off the rails though. I haven't really been
following this thread so please shoot me in my foot if I have put it
in my mouth.