linux-kernel - Re: [PATCH 01/15] sched/prio: Add a macro named NICE_TO

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Message-ID: <531EC748.5010600@cn.fujitsu.com>
Date:	Tue, 11 Mar 2014 16:20:24 +0800
From:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
CC:	linux-kernel@...r.kernel.org, joe@...ches.com,
	peterz@...radead.org, mingo@...nel.org, tglx@...utronix.de
Subject: Re: [PATCH 01/15] sched/prio: Add a macro named NICE_TO_RLIMIT in
 prio.h.

On 03/11/2014 04:17 PM, Heiko Carstens wrote:
> On Tue, Mar 11, 2014 at 12:59:16PM +0800, Dongsheng Yang wrote:
>> This patch add a macro named NICE_TO_RLIMIT in prio.h to
>> convert nice value [19,-20] to rlimit style value [1,40].
>>
>> Signed-off-by: Dongsheng Yang <yangds.fnst@...fujitsu.com>
>> ---
>>   include/linux/sched/prio.h | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/include/linux/sched/prio.h b/include/linux/sched/prio.h
>> index ac32258..8e78c47 100644
>> --- a/include/linux/sched/prio.h
>> +++ b/include/linux/sched/prio.h
>> @@ -41,4 +41,9 @@
>>   #define TASK_USER_PRIO(p)	USER_PRIO((p)->static_prio)
>>   #define MAX_USER_PRIO		(USER_PRIO(MAX_PRIO))
>>   
>> +/*
>> + * Convert nice value [19,-20] to rlimit style value [1,40].
>> + */
>> +#define NICE_TO_RLIMIT(nice)	(MAX_NICE - nice + 1)
> Where is MAX_NICE defined? The s390 patch fails to compile.

MAX_NICE is defined in include/linux/sched/prio.h. It is applied in tip 
tree,
and not in mainline yet.
>
> Also you probably want at least extra braces around the 'nice' usage to
> avoid subtle side effects. (or make NICE_TO.. a function, whatever).

Yes, agree. Another question is that I am not sure when I need to use a 
macro
and when I should use a inline function.

Could you help to give me some sugguestion?

Thanx
>

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