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

To: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
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 17:28:55 -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, Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>
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On Wed, 2 Aug 2006, Jeremy Fitzhardinge wrote:

> Add "always lock'd" implementations of set_bit, clear_bit and
> change_bit and the corresponding test_and_ functions.  Also add
> "always lock'd" implementation of cmpxchg.  These give guaranteed
> strong synchronisation and are required for non-SMP kernels running on
> an SMP hypervisor.

I think I asked this before....

Would it not be simpler to always use the locked implementation on UP? At 
least when the kernel is compiled with hypervisor support? This is going 
to add yet another series of bit operations.


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