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[209.85.220.65]) by mx.google.com with SMTPS id x189sor9829547pfx.37.2019.06.05.09.42.30 for (Google Transport Security); Wed, 05 Jun 2019 09:42:30 -0700 (PDT) Received-SPF: pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@cmpxchg-org.20150623.gappssmtp.com header.s=20150623 header.b="EpK/aD4e"; spf=pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=cmpxchg.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=IR/5u8R+ftfvePhhPnEG7rK5T0D9AZJGfobf430HZK0=; b=EpK/aD4eGRpEC9hMVO208gbI/muqvw8jBmuMlOGu+QCJFEebWFWSoFCERzvwGvuL6K ZsZW1YedQmJCDs8eKJRuqXLHpxRuF8EZ0fn2kX/QObnsB/BRL2omZKd+WbVgXyaemLx6 nIziz08WC5m6Od5vkSTLH9UrAqUvEideQSFn7Kek1qFQR0L0B9Lr6mu9mZtZkMWsYh68 Lh26494NJ/EqpF12bz4dOK09y5nJtxJbA5Jt04y7H3ZUrW/7ymTys04XVtMiWIRbFDoZ avUuRe2ACDkCiyz75JTnDTlW2XCPbiknHuhU5mk9t7MeLU10/Q07/2PW5oCPCQB+ZlqU FFAg== X-Google-Smtp-Source: APXvYqxGZGo/d/XJokbeKLqRlqfQUskb3FoYJTPKNFpIC57YsPlwoH1CmnWwVKyEBqoYUEgWRbnDhQ== X-Received: by 2002:aa7:9e51:: with SMTP id z17mr48511176pfq.212.1559752950079; Wed, 05 Jun 2019 09:42:30 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::2:cd0c]) by smtp.gmail.com with ESMTPSA id q125sm44812419pfq.62.2019.06.05.09.42.28 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 05 Jun 2019 09:42:28 -0700 (PDT) Date: Wed, 5 Jun 2019 12:42:27 -0400 From: Johannes Weiner To: Roman Gushchin Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Shakeel Butt , Vladimir Davydov , Waiman Long 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190605024454.1393507-2-guro@fb.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > Signed-off-by: Roman Gushchin Acked-by: Johannes Weiner