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

[Mike Galbraith]

At 05:31 PM 1/13/2005 -0600, Jack O'Quin wrote:
> Arjan van de Ven <arjanv@xxxxxxxxxx> writes:
>
> > On Thu, Jan 13, 2005 at 04:25:08PM -0500, Lee Revell wrote:
> >> The basic issue is that the current semantics of SCHED_FIFO seem make
> >> the deadlock/data corruption due to runaway RT thread issue difficult.
> >> The obvious solution is a new scheduling class equivalent to SCHED_FIFO
> >> but with a mechanism for the kernel to demote the offending thread to
> >> SCHED_OTHER in an emergency.
> >
> > and this is getting really close to the original "counter proposal" to the
> > LSM module that was basically "lets make lower nice limit an rlimit, and
> > have -20 mean "basically FIFO" *if* the task behaves itself".
>
> Yes.  However, my tests have so far shown a need for "actual FIFO as
> long as the task behaves itself."

I for one wonder why that appears to be so.  What happens if you use 
SCHED_RR instead of SCHED_FIFO?

(ie is the problem just one of running out of slice at a bad time, or is it 
the dynamic priority adjustment)

        -Mike 

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