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SubjectRe: [PATCH 19/36] autonuma: memory follows CPU algorithm and task/mm_autonuma stats collection
On Wed, 22 Aug 2012, Andi Kleen wrote:
> Andrea Arcangeli <aarcange@redhat.com> writes:
> > + /*
> > + * Take the lock with irqs disabled to avoid a lock
> > + * inversion with the lru_lock. The lru_lock is taken
> > + * before the autonuma_migrate_lock in
> > + * split_huge_page. If we didn't disable irqs, the
> > + * lru_lock could be taken by interrupts after we have
> > + * obtained the autonuma_migrate_lock here.
> > + */
>
> Which interrupt code takes the lru_lock? That sounds like a bug.

Not a bug: the clearest example is end_page_writeback() calling
rotate_reclaimable_page(); but I think once you probe deeper, you
find some other mm/swap.c pagevec operations which may get called
from interrupt, and end up freeing unrelated PageLRU pages.

Hugh


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