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[Xen-devel] Re: [patch 2/8] Implement always-locked bit ops, for memory

To: Andi Kleen <ak@xxxxxxx>
Subject: [Xen-devel] Re: [patch 2/8] Implement always-locked bit ops, for memory shared with an SMP hypervisor.
From: Christoph Lameter <clameter@xxxxxxx>
Date: Wed, 2 Aug 2006 21:27:46 -0700 (PDT)
Cc: akpm@xxxxxxxx, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Ian Pratt <ian.pratt@xxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Chris Wright <chrisw@xxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxx
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On Thu, 3 Aug 2006, Andi Kleen wrote:

> > Thats a good goal but what about the rest of us who have to maintain 
> > additional forms of bit operations for all architectures. How much is this 
> > burden?
> I don't think it's that big an issue because most architectures either
> use always locked bitops already or don't need them because they don't do
> SMP.

Those architectures that always use locked bitops or dont need them would 
not need to be modified if we put this in a special fail. I think this is 
a i386 speciality here?

Those operations are only needed for special xen driver and not for 
regular kernel code!

> So it will be fine with just a asm-generic header that defines them
> to the normal bitops. Not much burden.

asm-generic/xen-bitops.h asm-i386/xen-bitops.h is even less of a burden 
and would only require a 

#include <asm/xen-bitops.h>

for those special xen drivers.

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