linux-kernel - Re: [PATCH] DLS: add dl_time_equal helper in deadline scheduler

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Date:	Mon, 09 Apr 2012 09:34:16 +0200
From:	Juri Lelli <juri.lelli@...il.com>
To:	Hillf Danton <dhillf@...il.com>
CC:	Dario Faggioli <raistlin@...ux.it>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] DLS: add dl_time_equal helper in deadline scheduler

Hi,

On 04/07/2012 09:49 AM, Hillf Danton wrote:
> Hi all
>
> A tiny helper, dl_time_equal, is added for easing readers.
>
> And dl_entity_preempt is redefined to be bool, and its comment is also changed.
>
> Signed-off-by: Hillf Danton<dhillf@...il.com>
> ---
>
> --- a/kernel/sched_dl.c	Sat Apr  7 15:00:28 2012
> +++ b/kernel/sched_dl.c	Sat Apr  7 15:20:10 2012
> @@ -16,16 +16,21 @@
>    */
>   static const struct sched_class dl_sched_class;
>
> -static inline int dl_time_before(u64 a, u64 b)
> +static inline bool dl_time_equal(u64 a, u64 b)
> +{
> +	return a == b;
> +}
> +
> +static inline bool dl_time_before(u64 a, u64 b)
>   {
>   	return (s64)(a - b)<  0;
>   }
>
>   /*
> - * Tells if entity @a should preempt entity @b.
> + * Return true if entity @a could preempt entity @b in term of deadline
>    */
> -static inline
> -int dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b)
> +static inline bool
> +dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b)
>   {
>   	return dl_time_before(a->deadline, b->deadline);
>   }
> @@ -885,7 +890,7 @@ static void check_preempt_curr_dl(struct
>   	 * In the unlikely case current and p have the same deadline
>   	 * let us try to decide what's the best thing to do...
>   	 */
> -	if ((s64)(p->dl.deadline - rq->curr->dl.deadline) == 0&&
> +	if (dl_time_equal(p->dl.deadline, rq->curr->dl.deadline)&&
>   	!need_resched())
>   		check_preempt_equal_dl(rq, p);
>   #endif /* CONFIG_SMP */
> --

I'll change the comparison to be deadline_a == deadline_b, but I don't see the
need for a special helper function. It is used only once, better to have the
comparison really inline (a very special case).

Thanks and Regards,

- Juri
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