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Date:   Wed, 5 Jun 2019 12:42:27 -0400
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Roman Gushchin <guro@fb.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kernel-team@fb.com,
        Shakeel Butt <shakeelb@google.com>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Waiman Long <longman@redhat.com>
Subject: Re: [PATCH v6 01/10] mm: add missing smp read barrier on getting
 memcg kmem_cache pointer
Message-ID: <20190605164227.GB12453@cmpxchg.org>
References: <20190605024454.1393507-1-guro@fb.com>
 <20190605024454.1393507-2-guro@fb.com>
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On Tue, Jun 04, 2019 at 07:44:45PM -0700, Roman Gushchin 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@cmpxchg.org>
> Signed-off-by: Roman Gushchin <guro@fb.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>