Re: [BUG] 2.6.6-rc2-bk5 mm/slab.c change broke x86-64 SMP

From: Andi Kleen
Date: Fri Apr 30 2004 - 21:04:43 EST


On Fri, Apr 30, 2004 at 07:01:02PM -0700, Andrew Morton wrote:
> Andi Kleen <ak@xxxxxxx> wrote:
> >
> > > Does this fix?
> > >
> > > diff -puN include/asm-x86_64/processor.h~a include/asm-x86_64/processor.h
> > > --- 25/include/asm-x86_64/processor.h~a Fri Apr 30 11:24:58 2004
> > > +++ 25-akpm/include/asm-x86_64/processor.h Fri Apr 30 11:25:28 2004
> > > @@ -20,6 +20,8 @@
> > > #include <asm/mmsegment.h>
> > > #include <linux/personality.h>
> > >
> > > +#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
> >
> > 16 should be enough actually. The problem is the FXSAVE instruction that
> > is used to switch the FPU state, and that only requires 16 byte alignment.
> >
>
> yup. I sent Linus the patch which changes the default from 0 to
> L1_CACHE_SIZE in kernel/fork.c. x86_64 can override that by setting
> ARCH_MIN_TASKALIGN to 16 in asm/processor.h

Ok, I will change it in my next patchkit.

For i386 it is the same - 16 should be enough.

-Andi
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