On Mon, 30 Jan 2012, Tejun Heo wrote: > On Mon, Jan 30, 2012 at 09:15:58AM -0800, 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). > > Another thing is that percpu address dereferencing always goes through > rather unintuitive translation and 1. we can't (or rather currently > don't) guarantee that fault will occur for any address 2. even if it > does, the faulting address wouldn't be anything easily > distinguishible. So, unless the above shortcomings is resolved, I > don't really see much point of using ZERO_SIZE_PTR for percpu > allocator. The same is true for the use of NULL pointers. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>