linux-kernel - Re: [PATCH 2/3] sched: Use clamp() and clamp

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Date:	Wed, 05 Mar 2014 07:17:36 -0800
From:	Joe Perches <joe@...ches.com>
To:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, fweisbec@...il.com,
	rostedt@...dmis.org, peterz@...radead.org, mingo@...hat.com,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 2/3] sched: Use clamp() and clamp_val() to make it more
 readable.

On Wed, 2014-03-05 at 20:36 +0800, Dongsheng Yang wrote:
> As Kees suggested, I use clamp() function to replace the if and
> else branch, making it more readable and modular.
> 
> Suggested-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Dongsheng Yang <yangds.fnst@...fujitsu.com>
[]
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
[]
> @@ -3070,17 +3070,10 @@ SYSCALL_DEFINE1(nice, int, increment)
>  	 * We don't have to worry. Conceptually one call occurs first
>  	 * and we have a single winner.
>  	 */
> -	if (increment < -40)
> -		increment = -40;
> -	if (increment > 40)
> -		increment = 40;
> -
> +	increment = clamp(increment, -40, 40);

Maybe:

	increment = clamp(increment, -(NICE_MAX - NICE_MIN + 1), 
				   , NICE_MAX - NICE_MIN + 1)

or add yet another define like #define NICE_RANGE
or #define NICE_MAX_INCREMENT

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