linux-kernel - Re: [PATCH v2 01/11] mm/slab: fix the theoretical race by holding proper lock

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Date:	Thu, 14 Apr 2016 10:56:40 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/11] mm/slab: fix the theoretical race by holding
 proper lock

On Tue, Apr 12, 2016 at 11:38:39AM -0500, Christoph Lameter wrote:
> On Tue, 12 Apr 2016, js1304@...il.com wrote:
> 
> > @@ -2222,6 +2241,7 @@ static void drain_cpu_caches(struct kmem_cache *cachep)
> >  {
> >  	struct kmem_cache_node *n;
> >  	int node;
> > +	LIST_HEAD(list);
> >
> >  	on_each_cpu(do_drain, cachep, 1);
> >  	check_irq_on();
> > @@ -2229,8 +2249,13 @@ static void drain_cpu_caches(struct kmem_cache *cachep)
> >  		if (n->alien)
> >  			drain_alien_cache(cachep, n->alien);
> >
> > -	for_each_kmem_cache_node(cachep, node, n)
> > -		drain_array(cachep, n, n->shared, 1, node);
> > +	for_each_kmem_cache_node(cachep, node, n) {
> > +		spin_lock_irq(&n->list_lock);
> > +		drain_array_locked(cachep, n->shared, node, true, &list);
> > +		spin_unlock_irq(&n->list_lock);
> > +
> > +		slabs_destroy(cachep, &list);
> 
> Can the slabs_destroy() call be moved outside of the loop? It may be
> faster then?

Yes, it can. But, I'd prefer to call it on each node. It would be
better for cache although it would be marginal.

Thanks.