Re: mmotm 2010-01-06-14-34 uploaded (kernel/cgroup)

From: Li Zefan
Date: Wed Jan 06 2010 - 22:05:11 EST


>>>>> 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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