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Date: Tue, 21 Aug 2007 14:07:00 -0500
From: Joel Schopp <jschopp@austin.ibm.com>
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To: Nick Piggin <npiggin@suse.de>
Subject: Re: [patch 1/2] powerpc: rmb fix
References: <20070821021143.GB2909@wotan.suse.de>
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Cc: linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>
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>  #define mb()   __asm__ __volatile__ ("sync" : : : "memory")
> -#define rmb()  __asm__ __volatile__ (__stringify(LWSYNC) : : : "memory")
> +#define rmb()  __asm__ __volatile__ ("sync" : : : "memory")
>  #define wmb()  __asm__ __volatile__ ("sync" : : : "memory")
>  #define read_barrier_depends()  do { } while(0)
>  
> @@ -42,7 +42,7 @@
>  #ifdef __KERNEL__
>  #ifdef CONFIG_SMP
>  #define smp_mb()	mb()
> -#define smp_rmb()	rmb()
> +#define smp_rmb()	__asm__ __volatile__ (__stringify(LWSYNC) : : : "memory")
>  #define smp_wmb()	eieio()
>  #define smp_read_barrier_depends()	read_barrier_depends()
>  #else

I had to think about this one for awhile.  It looks at first glance to be the right 
thing to do.  But I do wonder how long rmb() has been lwsync and if as a practical 
matter that has caused any problems?  If this isn't causing any problems maybe there 
is some loigic we are overlooking?