Re: [PATCH RFC] sched/deadline: Use the revised wakeup rule for suspending constrained dl tasks

[Peter Zijlstra]

On Thu, May 04, 2017 at 04:17:21PM +0200, Peter Zijlstra wrote:
> On Mon, Apr 24, 2017 at 05:18:35PM +0200, Daniel Bristot de Oliveira wrote:
> > +static void
> > +update_dl_revised_wakeup(struct sched_dl_entity *dl_se, struct rq *rq)
> > +{
> > +	u64 density = div64_u64(dl_se->dl_runtime << 20, dl_se->dl_deadline);
> > +	u64 laxity = dl_se->deadline - rq_clock(rq);
> > +
> > +	BUG_ON(laxity < 0);
> 
> Compiler will make that go away, by virtue of laxity being unsigned.

Also, so we want that to BUG (or even WARN) in a soft RT setting.
Remember, GEDF does not guarantee we make our deadlines.


> We use two difference CBS rules:

_different_, clearly I cannot type anymore either ;-)