linux-kernel - Re: [PATCH] sched/core: fix sched_rt_global

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Date:	Mon, 3 Feb 2014 10:53:02 +0100
From:	Henrik Austad <henrik@...tad.us>
To:	Juri Lelli <juri.lelli@...il.com>
Cc:	peterz@...radead.org, mingo@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/core: fix sched_rt_global_validate

On Fri, Jan 31, 2014 at 05:43:27PM +0100, Juri Lelli wrote:
> Don't compare sysctl_sched_rt_runtime against sysctl_sched_rt_period if
> the former is equal to RUNTIME_INF, otherwise disabling -rt bandwidth
> management always fails.
> 
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Juri Lelli <juri.lelli@...il.com>
> ---
>  kernel/sched/core.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 210a12a..5c0a304 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7477,7 +7477,8 @@ static int sched_rt_global_validate(void)
>  	if (sysctl_sched_rt_period <= 0)
>  		return -EINVAL;
>  
> -	if (sysctl_sched_rt_runtime > sysctl_sched_rt_period)
> +	if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
> +		(sysctl_sched_rt_runtime > sysctl_sched_rt_period))
>  		return -EINVAL;

Won't this be caught by the test above?

#define RUNTIME_INF ((u64)~0ULL)

which means that if sysctl_sched_rt_runtime is set to RUNTIME_INF, it will 
trigger on the previous test, and the first part of this test will always 
be true.

Or have I suffered catastrophic monday-morning braindamage?

-- 
Henrik Austad
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