Subject: Re: [patch 2/2] powerpc: optimise smp_wmb

From: Benjamin Herrenschmidt <[email-masked]>
Date: Wed, 21 May 2008 12:02:15 -0400

On Wed, 2008-05-21 at 17:47 +0200, Nick Piggin wrote:
> 
> OK, but I just don't understand what the problem is... your synch.h
> has
> 
> #ifdef __powerpc64__
> #define __SUBARCH_HAS_LWSYNC
> #endif
> 
> #ifdef __SUBARCH_HAS_LWSYNC
> #    define LWSYNC      lwsync
> #else
> #    define LWSYNC      sync
> #endif
> 

This is mostly useless then since lwsync is just a sync to a processor
that doesn't know it (it's a sync with a reservd bit set) :-) Or it's
just to make gas happy if you specify a processor type that doesn't have
lwsync ?

Paul, do we have a case of a 32 bits CPU that chokes on the added bit ?

Ben.