linux-kernel - Re: [patch 1/2] mm, slub: fix false-positive lockdep warning in free

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Thu, 24 Jul 2014 15:18:27 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Johannes Weiner <hannes@...xchg.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Pekka Enberg <penberg@...nel.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [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!
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/