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

To: Christoph Lameter <clameter@xxxxxxx>
Subject: [Xen-devel] Re: [patch 2/8] Implement always-locked bit ops, for memory shared with an SMP hypervisor.
From: Andi Kleen <ak@xxxxxxx>
Date: Thu, 3 Aug 2006 06:49:11 +0200
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 Thursday 03 August 2006 06:27, Christoph Lameter wrote:
> 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?


They could do a single line #include for asm-generic that defines them
to the normal bitops.

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

The Xen driver will be "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.

Well there might be reasons someone else uses this in the future too.
It's also not exactly Linux style - normally we try to add generic


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