Message-ID: <4B454F59.1030503@cn.fujitsu.com>
Date: Thu, 07 Jan 2010 11:04:57 +0800
From: Li Zefan <lizf@cn.fujitsu.com>
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To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
CC: Randy Dunlap <randy.dunlap@oracle.com>, akpm@linux-foundation.org,
       linux-kernel@vger.kernel.org, "menage@google.com" <menage@google.com>,
       kirill@shutemov.name
Subject: Re: mmotm 2010-01-06-14-34 uploaded (kernel/cgroup)
References: <201001062259.o06MxQrp023236@imap1.linux-foundation.org>	<20100106170849.d0d95c9b.randy.dunlap@oracle.com>	<20100107113154.a1fa0103.kamezawa.hiroyu@jp.fujitsu.com>	<4B4549CB.8000809@cn.fujitsu.com> <20100107114728.58166ce4.kamezawa.hiroyu@jp.fujitsu.com>
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>>>>> It contains the following patches against 2.6.33-rc3:
>>>> kernel/cgroup.c: In function 'cgroup_write_event_control':
>>>> kernel/cgroup.c:2949: error: implicit declaration of function 'eventfd_fget'
>>>> kernel/cgroup.c:2949: warning: assignment makes pointer from integer without a cast
>>>> kernel/cgroup.c:2955: error: implicit declaration of function 'eventfd_ctx_fileget'
>>>> kernel/cgroup.c:2955: warning: assignment makes pointer from integer without a cast
>>>> make[2]: *** [kernel/cgroup.o] Error 1
>>>>
>>> Hmm, how about this rather than adding #ifdefs..
>>> Paul, Li, how do you think ?
>> I think make CONFIG_CGROUPS select EVENTFD would be better.
>>
> Hm, as far as I know, SELECT is not recommended. But yes, it seems side-effect
> of select is small here. But I avoid it as much as possible, usually.
> 
> Moreover, in this case,
>   - EVENTFD is a feature which is enabled by default.
>   - cgroup is "Say N if unsure" config.
> 
> In this case, "depends on" is good.
> 

I thought we use "depends on" if it's obvious by the config name
that a config depends on another config, and use "select" otherwise.

Referring to Documentation/Kbuild/kconfig-language.txt:

        select should be used with care.
        ...
        In general use select only for non-visible symbols
        (no prompts anywhere) and for symbols with no dependencies.

It does suggest "depends on" is better. :)

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