From: Roman Gushchin <guro@fb.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Kernel Team <Kernel-team@fb.com>,
"Michal Hocko" <mhocko@kernel.org>,
Rik van Riel <riel@surriel.com>,
Shakeel Butt <shakeelb@google.com>,
Christoph Lameter <cl@linux.com>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
Waiman Long <longman@redhat.com>
Subject: Re: [PATCH v5 5/7] mm: rework non-root kmem_cache lifecycle management
Date: Tue, 28 May 2019 22:28:51 +0000 [thread overview]
Message-ID: <20190528222847.GE27847@tower.DHCP.thefacebook.com> (raw)
In-Reply-To: <20190528220353.GC26614@cmpxchg.org>
On Tue, May 28, 2019 at 06:03:53PM -0400, Johannes Weiner wrote:
> On Tue, May 21, 2019 at 01:07:33PM -0700, Roman Gushchin wrote:
> > + arr = rcu_dereference(cachep->memcg_params.memcg_caches);
> > +
> > + /*
> > + * Make sure we will access the up-to-date value. The code updating
> > + * memcg_caches issues a write barrier to match this (see
> > + * memcg_create_kmem_cache()).
> > + */
> > + memcg_cachep = READ_ONCE(arr->entries[kmemcg_id]);
>
> READ_ONCE() isn't an SMP barrier, it just prevents compiler
> muckery. This needs an explicit smp_rmb() to pair with the smp_wmb()
> on the other side.
I believe rcu_dereference()/rcu_assign_pointer()/... are better replacements.
>
> I realize you're only moving this code, but it would be good to fix
> that up while you're there.
Right. I'll try to fix it with new-ish rcu API in a separate patch
preceding this one.
Thank you for looking into the series!
next prev parent reply other threads:[~2019-05-28 22:29 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190521200735.2603003-1-guro@fb.com>
2019-05-22 21:43 ` [PATCH v5 0/7] mm: reparent slab memory on cgroup removal Roman Gushchin
2019-05-22 21:59 ` Andrew Morton
2019-05-22 22:23 ` Roman Gushchin
2019-05-28 7:01 ` Michal Hocko
[not found] ` <20190521200735.2603003-6-guro@fb.com>
2019-05-28 17:08 ` [PATCH v5 5/7] mm: rework non-root kmem_cache lifecycle management Vladimir Davydov
[not found] ` <96b8a923-49e4-f13e-b1e3-3df4598d849e@redhat.com>
2019-05-28 17:39 ` Vladimir Davydov
2019-05-28 17:41 ` Waiman Long
2019-05-28 18:00 ` Vladimir Davydov
2019-05-28 22:03 ` Johannes Weiner
2019-05-28 22:28 ` Roman Gushchin [this message]
[not found] ` <20190521200735.2603003-3-guro@fb.com>
2019-05-28 17:11 ` [PATCH v5 2/7] mm: generalize postponed non-root kmem_cache deactivation Vladimir Davydov
[not found] ` <20190521200735.2603003-5-guro@fb.com>
2019-05-28 17:12 ` [PATCH v5 4/7] mm: unify SLAB and SLUB page accounting Vladimir Davydov
2019-05-28 22:00 ` Johannes Weiner
[not found] ` <20190521200735.2603003-2-guro@fb.com>
2019-05-28 17:14 ` [PATCH v5 1/7] mm: postpone kmem_cache memcg pointer initialization to memcg_link_cache() Vladimir Davydov
2019-05-28 21:56 ` Johannes Weiner
[not found] ` <20190521200735.2603003-8-guro@fb.com>
2019-05-28 17:38 ` [PATCH v5 7/7] mm: fix /proc/kpagecgroup interface for slab pages Vladimir Davydov
[not found] ` <20190521200735.2603003-7-guro@fb.com>
2019-05-28 18:33 ` [PATCH v5 6/7] mm: reparent slab memory on cgroup removal Vladimir Davydov
2019-05-28 19:58 ` Roman Gushchin
2019-05-28 20:11 ` Vladimir Davydov
2019-05-28 21:52 ` Roman Gushchin
2019-05-28 22:16 ` Johannes Weiner
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