From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 62F96C49ED7 for ; Fri, 20 Sep 2019 12:29:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3718A20665 for ; Fri, 20 Sep 2019 12:29:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GNbjA0OL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2408999AbfITM3M (ORCPT ); Fri, 20 Sep 2019 08:29:12 -0400 Received: from mail-lj1-f193.google.com ([209.85.208.193]:45137 "EHLO mail-lj1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404619AbfITM3L (ORCPT ); Fri, 20 Sep 2019 08:29:11 -0400 Received: by mail-lj1-f193.google.com with SMTP id q64so6850145ljb.12 for ; Fri, 20 Sep 2019 05:29:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :user-agent; bh=zRqTS3V+m+4w0d7L5MeANtoAWhuIONw+ofn7LfLax7M=; b=GNbjA0OLqlXcmqK1epU19sHUETfXuc5bNucGPbu43hbBJRRCHB84gR38mBnRnV4QDn IsLVHtJ/kjm4u7fOP6Xnu/6GT+JJyZBaOnsg6ZJijLJnhT5zeOg9QWCV0kWvAAbLFriF O50eGu7iyy1t1jvOHVL5qWjQ7YgiuPKF6YtZxDRY1ymTQljCalRidsAh/YRtDx13VLkd +ydRU7HEhHJlDDdy5aCCUk5PhtNQ7vpwRDXzpV9Jlwzbs5BcBPrTgXlXehqdant/eC2d PXKCsTgY02l6NJsYzdfLbI6nUsWt8jgtQdnJiUAWfOqwxIWCpigPQVr4pg+cp1Y97Z9Z PmKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:user-agent; bh=zRqTS3V+m+4w0d7L5MeANtoAWhuIONw+ofn7LfLax7M=; b=h5WqRiZxGnuqF+RwexQCqHw+/3qo75XoT2I6N9KKVz/gAPv46p1sOlxhqpCtpSZR6r W1g4wx+3J1anLmRqyRF0CUjRwD7NcykHViliRYB5gAofZk1KgCIBGgslrT+B5iCchZt5 IyOILlOdN5DRVOtOnWlSlZIHcVnUvS0q3vgFEpjtEzjkbdle5yKsMMJTS9cpfyHjJGdQ 462W3GshG+KLPlY478HKMqXUuXdUSp1psFTq3wW1IXzxyX33OVgjJVs0xT++KCchPH4z XwBJHZv6nJ1OnKa78/f7tRXWrGSAj0CSAovkO1xYJ09lTr9oTQ1MCxBIIIvwxdo8T3zJ PczQ== X-Gm-Message-State: APjAAAU9gLdhAInByaWLl8iES5dnU63JectuV8/sXZbgFYerpR7TmjA3 N12bl9D2nnIlJB6F94PiRtE= X-Google-Smtp-Source: APXvYqysZ6X7F0kXPqDsa2l37Rkz7d6wWrYJIuXm6C88aYt/3zLc9GrhGdjYqnFW1nniutXZSOKk2A== X-Received: by 2002:a2e:6804:: with SMTP id c4mr9364426lja.120.1568982549984; Fri, 20 Sep 2019 05:29:09 -0700 (PDT) Received: from uranus.localdomain ([5.18.103.226]) by smtp.gmail.com with ESMTPSA id z72sm418739ljb.98.2019.09.20.05.29.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Sep 2019 05:29:08 -0700 (PDT) Received: by uranus.localdomain (Postfix, from userid 1000) id ED22E461797; Fri, 20 Sep 2019 15:29:07 +0300 (MSK) Date: Fri, 20 Sep 2019 15:29:07 +0300 From: Cyrill Gorcunov To: LKML Cc: Linux MM , Johannes Weiner , Michal Hocko , Vladimir Davydov , Kirill Tkhai Subject: [PATCH] mm, memcg: assign shrinker_map before kvfree Message-ID: <20190920122907.GG2507@uranus.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently there is a small gap between fetching pointer, calling kvfree and assign its value to nil. In current callgraph it is not a problem (since memcg_free_shrinker_maps is running from memcg_alloc_shrinker_maps and mem_cgroup_css_free only) still this looks suspicious and we can easily eliminate the gap at all. Cc: Johannes Weiner Cc: Michal Hocko Cc: Vladimir Davydov Cc: Kirill Tkhai Signed-off-by: Cyrill Gorcunov --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-tip.git/mm/memcontrol.c =================================================================== --- linux-tip.git.orig/mm/memcontrol.c +++ linux-tip.git/mm/memcontrol.c @@ -364,9 +364,9 @@ static void memcg_free_shrinker_maps(str for_each_node(nid) { pn = mem_cgroup_nodeinfo(memcg, nid); map = rcu_dereference_protected(pn->shrinker_map, true); + rcu_assign_pointer(pn->shrinker_map, NULL); if (map) kvfree(map); - rcu_assign_pointer(pn->shrinker_map, NULL); } }