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

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Message-ID: <485ABD3A.9090704@uw.no>
Date:	Thu, 19 Jun 2008 20:10:34 +0000
From:	"Daniel K." <dk@...no>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
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

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.


Daniel K.

> ---
>  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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