Re: [PATCHv2] bitops: add _local bitops

[Christoph Lameter]

On Wed, 9 May 2012, Michael S. Tsirkin wrote:

> kvm needs to update some hypervisor variables atomically
> in a sense that the operation can't be interrupted
> in the middle. However the hypervisor always runs
> on the same CPU so it does not need any memory
> barrier or lock prefix.
>
> Add _local bitops for this purpose: define them
> as non-atomics for x86 and (for now) atomics for
> everyone else.

Have you tried to use the this_cpu_ops for that purpose? They create the
per cpu atomic instructions that you want without a lock prefix and can
also relocate the per cpu pointer to the correct processor via a
segment register prefix.

There are no bit operations provided right now but those can either be
improvised using this_cpu_cmpxchg or added.
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