[PATCH 1/3] percpu: use ZERO_SIZE_PTR / ZERO_OR_NULL_PTR

[Christoph Lameter]

On Mon, 30 Jan 2012, Tejun Heo wrote:

> Percpu pointers are in a different address space and using
> ZERO_SIZE_PTR directly will trigger sparse address space warning.
> Also, I'm not entirely sure whether 16 is guaranteed to be unused in
> percpu address space (maybe it is but I don't think we have anything
> enforcing that).

We are already checking for NULL on free. So there is a presumption that
these numbers are unused.