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SubjectRe: [PATCH] percpu: fix unit_map[] verification in pcpu_setup_first_chunk()
Christoph Lameter wrote:
> On Tue, 29 Sep 2009, Tejun Heo wrote:
>
>> pcpu_setup_first_chunk() incorrectly used NR_CPUS as the impossible
>> unit number while unit number can equal and go over NR_CPUS with
>> sparse unit map. This triggers BUG_ON() spuriously on machines which
>> have non-power-of-two number of cpus. Use UINT_MAX instead.
>
> Uhhh. Funky. The assumption nr_cpu_ids < NR_CPUS has been broken. Wonder
> what other effects that will have. In particular since the slab and page
> allocators have arrays indexed by the cpu number and those arrays are
> dimensioned for NR_CPUS.

Heh.. that's not what's broken. unit# can legally go over NR_CPUS or
nr_cpu_ids as cpus can be sparsely mapped to units. The problem is
that I didn't fix unit_map allocation. Will update the patch. Just a
sec.

--
tejun


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