Re: [PATCH 19/36] autonuma: memory follows CPU algorithm andtask/mm_autonuma stats collection

[Hugh Dickins]

On Wed, 22 Aug 2012, Andi Kleen wrote:
> Andrea Arcangeli <aarcange@xxxxxxxxxx> 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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