linux-kernel - Re: 2.6.23-rc3-mm1

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Message-ID: <20070823162553.GB30504@skynet.ie>
Date:	Thu, 23 Aug 2007 17:25:53 +0100
From:	mel@...net.ie (Mel Gorman)
To:	Andi Kleen <ak@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Sam Ravnborg <sam@...nborg.org>
Subject: Re: 2.6.23-rc3-mm1

On (23/08/07 14:07), Andi Kleen didst pronounce:
> On Wed, Aug 22, 2007 at 11:10:29AM -0700, Andrew Morton wrote:
> > x86_64-mm-less-stack-alignment.patch has
> > 
> > cflags-y += $(call cc-option,-mpreferred-stack-boundary=3)
> > 
> > So we _should_ have detected that gcc didn't like =3, so it
> > should not have been used.
> 
> The flag actually needs a recent gcc 4.3 snapshot (it's
> a new feature the gcc developers added especially for the
> kernel :), so if this didn't work it would fail on the vast 
> majority of systems.
> 
> Somehow it doesn't? At least here it compiles fine.
> 
> I notice the final comma is missing, Mel does it work
> when you change the line to 
> 
> cflags-y += $(call cc-option,-mpreferred-stack-boundary=3,)  
> 

No but that is hardly a suprise as it's looking like -m64 is the way
forward.

> If not please run
> gcc -O2 -mpreferred-stack-boundary=2 -S -xc /dev/null -o x.o 
> echo $?
> 
> What does the echo output?
> 

Repeating really but;

elm3b6:~# gcc -O2 -mpreferred-stack-boundary=2 -S -xc /dev/null -o x.o ; echo $?
0
elm3b6:~# gcc -m64 -O2 -mpreferred-stack-boundary=2 -S -xc /dev/null -o x.o ; echo $?
/dev/null:1: error: -mpreferred-stack-boundary=2 is not between 4 and 12
1


-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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