Messages in this thread | | | Date | Wed, 02 Dec 2009 08:31:44 +0200 | From | Pekka Enberg <> | Subject | Re: Q, slab, kmemleak_erase() and redzone? |
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Catalin Marinas kirjoitti: > On Tue, 2009-12-01 at 11:49 +0000, Pekka Enberg wrote: >> hooanon05@yahoo.co.jp kirjoitti: >>> Pekka Enberg: >>>> We are setting an element in the per CPU array to NULL so the the >>>> kmemleak code in ____cache_alloc() is safe. Red-zoning is done at the >>>> _object_ which is not touched by kmemleak. Looking at the oops, it >>>> does seem likely that you have a bug in your module (or in some other >>>> part of the kernel). >>> Thanks for reply. >>> In ____cache_alloc(), the variable 'ac' is assigned before >>> cache_alloc_refill() call, and it is used for the parameter of >>> kmemleak_erase(). The value may be changed by cache_alloc_refill(), >>> isn't it? >> No. The pointer returned by cpu_cache_get() is not changed by >> cache_alloc_refill(). The contents of the array might change, yes. That >> said, we should check if objp is NULL before calling kmemleak_erase(). > > Possibly but I don't understand why that's needed. The kmemleak_erase() > call just sets the ac->entry[ac->avail] to NULL. If ac->avail is 0, it > doesn't cause any harm.
No, you are absolutely correct. Can you please send an updated patch to Catalin that adds a comment on top of the cpu_cache_get() call that explains why we need it there?
Pekka
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