Messages in this thread | | | Date | Mon, 30 Jan 2012 11:22:57 -0600 (CST) | From | Christoph Lameter <> | Subject | Re: [PATCH 1/3] percpu: use ZERO_SIZE_PTR / ZERO_OR_NULL_PTR |
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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.
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