linux-kernel - Re: [PATCH 10/10] sched: rt: dont stop the period timer when there are tasks wanting to run

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Date:	Thu, 19 Jun 2008 22:16:17 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	"Daniel K." <dk@...no>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 10/10] sched: rt: dont stop the period timer when there
	are tasks wanting to run

On Thu, 2008-06-19 at 20:10 +0000, Daniel K. wrote:
> Peter Zijlstra wrote:
> > When a runnable group failed to get any runtime within a period it would be
> > found idle and the period timer would be stopped.
> > 
> > So if the group ever gets throttled, it will never wake up again.
> > 
> > Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > Reported-by: "Daniel K." <dk@...no>
> Tested-by: Daniel K. <dk@...no>
> 
> I think this should go into .26 as well, due to the non-intuitiveness
> of the knobs that cause this if they are fiddled with in the wrong way.

Sounds reasonable, Ingo?

> > ---
> >  kernel/sched_rt.c |    3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > Index: linux-2.6/kernel/sched_rt.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/sched_rt.c
> > +++ linux-2.6/kernel/sched_rt.c
> > @@ -408,7 +408,8 @@ static int do_sched_rt_period_timer(stru
> >  			if (rt_rq->rt_time || rt_rq->rt_nr_running)
> >  				idle = 0;
> >  			spin_unlock(&rt_rq->rt_runtime_lock);
> > -		}
> > +		} else if (rt_rq->rt_nr_running)
> > +			idle = 0;
> >  
> >  		if (enqueue)
> >  			sched_rt_rq_enqueue(rt_rq);
> > 
> 

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