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

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.