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SubjectRe: [patch 1/2] mm, slub: fix false-positive lockdep warning in free_partial()
On Thu, 24 Jul 2014, Johannes Weiner wrote:

> > diff --git a/mm/slub.c b/mm/slub.c
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -3195,12 +3195,13 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
> > /*
> > * Attempt to free all partial slabs on a node.
> > * This is called from kmem_cache_close(). We must be the last thread
> > - * using the cache and therefore we do not need to lock anymore.
> > + * using the cache, but we still have to lock for lockdep's sake.
> > */
> > static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
> > {
> > struct page *page, *h;
> >
> > + spin_lock_irq(&n->list_lock);
> > list_for_each_entry_safe(page, h, &n->partial, lru) {
> > if (!page->inuse) {
> > __remove_partial(n, page);
>
> This already uses __remove_partial(), which does not have the lockdep
> assertion. You even acked the patch that made this change, why add
> the spinlock now?
>

Yup, thanks. This was sitting in Pekka's slab/next branch but isn't
actually needed after commit 1e4dd9461fab ("slub: do not assert not
having lock in removing freed partial"). Good catch!


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