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    SubjectRe: [PATCH 9/10] mm/memcg: move lru_lock into lruvec
    On Wed, 22 Feb 2012, Konstantin Khlebnikov wrote:
    > Hugh Dickins wrote:
    > >
    > > I'll have to come back to think about your locking later too;
    > > or maybe that's exactly where I need to look, when investigating
    > > the mm_inline.h:41 BUG.
    >
    > pages_count[] updates looks correct.
    > This really may be bug in locking, and this VM_BUG_ON catch it before
    > list-debug.

    I've still not got into looking at it yet.

    You're right to mention DEBUG_LIST: I have that on some of the machines,
    and I would expect that to be the first to catch a mislocking issue.

    In the past my problems with that BUG (well, the spur to introduce it)
    came from hugepages.

    > >
    > > But at first sight, I have to say I'm very suspicious: I've never found
    > > PageLRU a good enough test for whether we need such a lock, because of
    > > races with those pages on percpu lruvec about to be put on the lru.
    > >
    > > But maybe once I look closer, I'll find that's handled by your changes
    > > away from lruvec; though I'd have thought the same issue exists,
    > > independent of whether the pending pages are in vector or list.
    >
    > Are you talking about my per-cpu page-lists for lru-adding?

    Yes.

    > This is just an unnecessary patch, I don't know why I include it into v2 set.
    > It does not protect anything.

    Okay.

    Hugh


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