30 Jan
2012
30 Jan
'12
5:35 p.m.
On Mon, 30 Jan 2012, Tejun Heo wrote:
I'm pretty sure it never gives out NULL for a dynamic allocation. The base might be mapped to zero but we're guaranteed to have some static percpu areas there and IIRC the percpu addresses aren't supposed to wrap.
True but there is a check for a NULL pointer on free. So a NULL pointer currently has the semantics of being an unallocated per cpu structure. If the allocator returns NULL by accident then we cannot free the per cpu allocation anymore.