linux-kernel - Re: [PATCHSET core/percpu] percpu: convert most archs to dynamic percpu

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Date:	Wed, 20 May 2009 10:41:20 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Tejun Heo <tj@...nel.org>
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,
	jesper.nilsson@...s.com, dhowells@...hat.com,
	ysato@...rs.sourceforge.jp, tony.luck@...el.com,
	takata@...ux-m32r.org, geert@...ux-m68k.org, monstr@...str.eu,
	ralf@...ux-mips.org, kyle@...artin.ca, benh@...nel.crashing.org,
	paulus@...ba.org, heiko.carstens@...ibm.com, lethal@...ux-sh.org,
	davem@...emloft.net, jdike@...toit.com, chris@...kel.net,
	rusty@...tcorp.com.au
Subject: Re: [PATCHSET core/percpu] percpu: convert most archs to dynamic
 percpu

On Wed, 20 May 2009 16:37:32 +0900
Tejun Heo <tj@...nel.org> wrote:

> Hello,
> 
> Please do NOT pull before maintainers of alpha and s390 ack.  Upon
> ack, please pull from the following git tree.
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git tj-percpu
> 
> This patchset is combination of the last patch of
> percpu-use-dynamic-percpu-allocator-as-default patchset[1] and patches
> inspired by alpha conversion patch[2] posted by Ivan Kokshaysky.
> 
>   0001-percpu-use-dynamic-percpu-allocator-as-the-default.patch
>   0002-linker-script-throw-away-.discard-section.patch
>   0003-percpu-clean-up-percpu-variable-definitions.patch
>   0004-percpu-enforce-global-uniqueness-and-disallow-in-fu.patch
>   0005-alpha-kill-unnecessary-__used-attribute-in-PER_CPU_.patch
>   0006-alpha-switch-to-dynamic-percpu-allocator.patch
>   0007-s390-switch-to-dynamic-percpu-allocator.patch
> 
> 0001 is mostly unchanged except for added Acked-by's.
> 
> 0002-0003 prepare for percpu variable definition update - .discard is
> thrown away on all archs when linking kernel and modules, static
> percpu variables in functions are moved outside of the function and
> all static percpu variables are given unique names.
> 
> 0004 updates percpu variable definition such that all percpu variables
> in the same link unit have unique names regardless of its scope
> (static or global) and disallow in-function static definitions.  The
> new definition uses dummy variables in .discard to enforce the
> declaration/definition semantics and always defines percpu variables
> as globals.  This allows archs to add 'weak' attribute if necessary.
> 
> 0005-0006 converts alpha to use 'weak' attribute instead of inline
> assembly to generate GOT based reference when referencing percpu
> variables from modules, which in turn allows conversion to dynamic
> percpu allocator.
> 
> 0007 does the same for s390.
> 
> The new DECLARE/DEFINE macros implement the following behaviors.
> 
> a. DECLARE + static DEFINE -> compile error
> 
> b. multiple non-static DEFINEs with the same name -> compile error
> 
> c. multiple static/global DEFINEs with the same name -> compile error
> 
> d. in function static DEFINEs -> compile error
> 
> #a and #b are expected behaviors on DECLARE/DEFINE macros in general.
> #c and #d are necessary to allow 'weak' attribute on certain archs.
> Please note that the rules are applied consistently whether 'weak'
> attribute is specified or not.  This eases catching mistakes and makes
> things less confusing.
> 
> Test config boots and works fine on x86_64.  alpha and s390 are
> compile tested and verified to generate necessary code for external
> references but I don't have any way to actually verify them, so please
> test them.  :-)
> 
> all-yes-config on x86_64 is building now.  Ergggh... I want more
> memory.  Okay, completed successfully.

Just tested the patch-series on s390. Works fine:
Acked-by: Martin Schwidefsky <schwidefsky@...ibm.com>

Kudos to Tejun and Ivan :-)

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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