linux-kernel - Re: [PATCH 3/7] percpu: clean up percpu variable definitions

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Date:	Tue, 26 May 2009 01:07:16 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	mingo@...e.hu, linux-kernel@...r.kernel.org, x86@...nel.org,
	ink@...assic.park.msu.ru, rth@...ddle.net, linux@....linux.org.uk,
	hskinnemoen@...el.com, cooloney@...nel.org, starvik@...s.com,
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	heiko.carstens@...ibm.com, lethal@...ux-sh.org,
	davem@...emloft.net, jdike@...toit.com, chris@...kel.net,
	Jens Axboe <jens.axboe@...cle.com>,
	Dave Jones <davej@...hat.com>,
	Jeremy Fitzhardinge <jeremy@...source.com>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH 3/7] percpu: clean up percpu variable definitions

Rusty Russell wrote:
> On Wed, 20 May 2009 05:07:35 pm Tejun Heo wrote:
>> Percpu variable definition is about to be updated such that
>>
>> * percpu symbols must be unique even the static ones
>>
>> * in-function static definition is not allowed
> 
> That spluttering noise is be choking on the title of this patch :)
> 
> Making these pseudo statics is in no way a cleanup.  How about we just
> say "they can't be static" and do something like:
> 
> /* Sorry, can't be static: that breaks archs which need these weak. */
> #define DEFINE_PER_CPU(type, var) \
> 	extern typeof(type) var; DEFINE_PER_CPU_SECTION(type, name, "")

Heh... well, even though I authored the patch, I kind of agree with
you.  Maybe it would be better to simply disallow static declaration /
definition at all.  I wanted to give a go at the original idea as it
seemed to have some potential.  The result isn't too disappointing but
I can't really say there are distinctively compelling advantages to
justify the added complexity and subtlety.

What do others think?  Is everyone happy with going extern only?

Thanks.

-- 
tejun
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