linux-kernel - Re: [PATCH] x86: fix find_next_bit breakage on ppc and powerpc

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Date:	Thu, 17 Apr 2008 11:04:37 +0200
From:	"Alexander van Heukelum" <heukelum@...tmail.fm>
To:	"Paul Mackerras" <paulus@...ba.org>, "Ingo Molnar" <mingo@...e.hu>,
	linuxppc-dev@...abs.org
Cc:	"Alexander van Heukelum" <heukelum@...lshack.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: fix find_next_bit breakage on ppc and powerpc

On Thu, 17 Apr 2008 08:55:12 +1000, "Paul Mackerras" <paulus@...ba.org>
said:
> Ingo Molnar writes:
> > 
> > * Alexander van Heukelum <heukelum@...lshack.com> wrote:
> > 
> > > Powerpc (and ppc) have their have some code in their bitops.h which 
> > > used to be exacly the same as asm-generic/bitops/find.h. Include this 
> > > header instead.
> > > 
> > > This should also fix the compile problems due to the generic 
> > > find_next_bit changes. Those were fixed by Thomas Gleixner in 
> > > asm-generic/bitops/find.h earlier.
> > > 
> > > Signed-off-by: Alexander van Heukelum <heukelum@...tmail.fm>
> > 
> > thanks, applied. I dropped:
> 
> Why are powerpc (and ppc) patches
> - not being sent to the powerpc maintainer (me)
> - not being cc'd to the linuxppc-dev@...abs.org list
> - ending up going through the x86 tree?

Hello,

My apologies for that. The patches that are now in x86#testing were
needed because of changes I introduced. Thomas Gleixner found a
problem with the patches that caused compile problems for basically
all archs with GENERIC_FIND_NEXT_BIT=y, and his fix was to change
asm-generic/bitops/find.h. However, ppc and powerpc did things
differently... (x86 too, but they have special permissions ;) )

(Better late than never) Please consider applying the patch in
        http://lkml.org/lkml/2008/4/16/107
as:

[PATCH] powerpc: use asm-generic/bitops/find.h in bitops.h

Powerpc (and ppc) have some code in their bitops.h that is
exacly the same as asm-generic/bitops/find.h. Include this
header instead of the private implementation.

> How come patches to unify x86_32 and x86_64 bitops need to end up
> touching powerpc?

This was not a pure unification. Originally I wanted to convert
both x86_64 and i386 to the existing generic bitops. Andi Kleen,
however, objected because x86_64 would than lose a certain
optimization for small bitmaps. I moved this optimization to
the generic code, and broke non-x86. Everyone except ppc/powerpc
was fixed by Thomas Gleixner (in a generic header file).
http://lkml.org/lkml/2008/4/16/107 just changes ppc/powerpc in
such a way that Thomas' fix works there too.

Greetings,
    Alexander

> Paul.
-- 
  Alexander van Heukelum
  heukelum@...tmail.fm

-- 
http://www.fastmail.fm - The professional email service

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