Re: [PATCH v6 01/10] mm: add missing smp read barrier on getting memcg kmem_cache pointer
From: Roman Gushchin
Date: Wed Jun 05 2019 - 13:18:36 EST
On Tue, Jun 04, 2019 at 09:35:02PM -0700, Shakeel Butt wrote:
> On Tue, Jun 4, 2019 at 7:45 PM Roman Gushchin <guro@xxxxxx> wrote:
> > Johannes noticed that reading the memcg kmem_cache pointer in
> > cache_from_memcg_idx() is performed using READ_ONCE() macro,
> > which doesn't implement a SMP barrier, which is required
> > by the logic.
> > Add a proper smp_rmb() to be paired with smp_wmb() in
> > memcg_create_kmem_cache().
> > The same applies to memcg_create_kmem_cache() itself,
> > which reads the same value without barriers and READ_ONCE().
> > Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> > Signed-off-by: Roman Gushchin <guro@xxxxxx>
> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
> This seems like independent to the series. Shouldn't this be Cc'ed stable?
It is independent, but let's keep it here to avoid merge conflicts.
It has been so for a long time, and nobody complained, so I'm not sure
if we really need a stable backport. Do you have a different opinion?