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    SubjectRe: [PATCH] slub: Fix sysfs circular locking dependency
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    On Wed, Jan 5, 2011 at 7:10 PM, Christoph Lameter <cl@linux.com> wrote:
    > How about this solution? In the common case of kernels without hotplug
    > support there will be no locking at all.
    >
    >
    > Subject: slub: Avoid use of slub_lock in show_slab_objects()
    >
    > The purpose of the locking is to prevent removal and additions
    > of nodes when statistics are gathered for a slab cache. So we
    > need to avoid racing with memory hotplug functionality.
    >
    > It is enough to take the memory hotplug locks there instead
    > of the slub_lock.
    >
    >
    > Signed-off-by: Christoph Lameter <cl@linux.com>
    >
    > ---
    >  mm/slub.c |    4 ++--
    >  1 file changed, 2 insertions(+), 2 deletions(-)
    >
    > Index: linux-2.6/mm/slub.c
    > ===================================================================
    > --- linux-2.6.orig/mm/slub.c    2011-01-05 09:55:34.000000000 -0600
    > +++ linux-2.6/mm/slub.c 2011-01-05 09:56:27.000000000 -0600
    > @@ -3821,7 +3821,7 @@ static ssize_t show_slab_objects(struct
    >                }
    >        }
    >
    > -       down_read(&slub_lock);
    > +       lock_memory_hotplug();
    >  #ifdef CONFIG_SLUB_DEBUG
    >        if (flags & SO_ALL) {
    >                for_each_node_state(node, N_NORMAL_MEMORY) {
    > @@ -3862,7 +3862,7 @@ static ssize_t show_slab_objects(struct
    >                        x += sprintf(buf + x, " N%d=%lu",
    >                                        node, nodes[node]);
    >  #endif
    > -       up_read(&slub_lock);
    > +       unlock_memory_hotplug();
    >        kfree(nodes);
    >        return x + sprintf(buf + x, "\n");
    >  }

    Makes sense. Bart, does this fix the problem for you?
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