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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 F06E3C2BB1D for ; Mon, 16 Mar 2020 14:59:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C76742071C for ; Mon, 16 Mar 2020 14:59:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584370768; bh=F8ExpDYTSm2ccZjcOgp7UIFc5x/0wMVp2nTW1OCy2rg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=XHJaiJw9qs/L+n2elOFyl3D7VhVd/0FMnZnwk9/a44MT5agXOSdhrKRsWulzny/Kg Wvptk/h3mXr2OVeJi03dPZiAseLhHtdh3h0rKnTrreBl266IU3FZrvt3RIb9zmr905 ZlFxSDCLOAYo6TmA/ZscSXPTnFtMz0ikkyrpkxRA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731772AbgCPO71 (ORCPT ); Mon, 16 Mar 2020 10:59:27 -0400 Received: from mail-wm1-f65.google.com ([209.85.128.65]:50341 "EHLO mail-wm1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731629AbgCPO71 (ORCPT ); Mon, 16 Mar 2020 10:59:27 -0400 Received: by mail-wm1-f65.google.com with SMTP id z13so1971913wml.0; Mon, 16 Mar 2020 07:59:25 -0700 (PDT) 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:references :mime-version:content-disposition:in-reply-to; bh=4FvxAgszQ++g/zBJBmYryRtulzv92eq2k64hW2XTxyI=; b=KJ8dn3BzFIyRA9SGk+20C70HQStvMy0R6edJhIefx0BKO6p40F9Odbb6/uK3VZGdWi gMXr5hFNeJ9gFLQIFMaI5DI1X8eskmWZ4q5ySvDKSB/dp+mZQ8ezXTU3qDC/Agq64pFJ MEBT4pIJo4ebRc4lLVKSV5AATOR19zBpQdHcgYFsVFZS0eE5SYuM1yZnEgWy9Yj7Rb3O j/2JbOz0s6Mnyuj6+K0C+DDptrSZmQuTlBQeiH5dAJ/Nh7xXZvVVa7/x0pwjCJFgfpyW TC+sdTNkRQ1azPgzVcasNShQnW3BZNtOu2pjMtLhq+eQuVSTklUNhSaCCkQTj6iljOY+ 1ClA== X-Gm-Message-State: ANhLgQ1mAU7FCjSvuAWuxkvOCMAEDvkj+IzexIveITSPjXbJdT7DGV4q pETQgri0MYMN2CpXmXE67+M= X-Google-Smtp-Source: ADFU+vsmj1xkbZ9kxBp+/4xkXEym15gDWpWFuxQ0MIWoC15PvOzXSMYHNNI+AHLL8TfC9S/gjtvdjg== X-Received: by 2002:a7b:c75a:: with SMTP id w26mr10572063wmk.2.1584370765264; Mon, 16 Mar 2020 07:59:25 -0700 (PDT) Received: from localhost ([37.188.132.163]) by smtp.gmail.com with ESMTPSA id i67sm256021wri.50.2020.03.16.07.59.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2020 07:59:24 -0700 (PDT) Date: Mon, 16 Mar 2020 15:59:23 +0100 From: Michal Hocko To: Chris Down Cc: Andrew Morton , Johannes Weiner , Tejun Heo , Roman Gushchin , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 6/6] mm, memcg: Prevent mem_cgroup_protected store tearing Message-ID: <20200316145923.GR11482@dhcp22.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 12-03-20 17:33:16, Chris Down wrote: > The read side of this is all protected, but we can still tear if > multiple iterations of mem_cgroup_protected are going at the same time. > > There's some intentional racing in mem_cgroup_protected which is ok, but > load/store tearing should be avoided. > > Signed-off-by: Chris Down > Cc: Andrew Morton > Cc: Johannes Weiner > Cc: Roman Gushchin > Cc: Tejun Heo > Cc: linux-mm@kvack.org > Cc: cgroups@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: kernel-team@fb.com Acked-by: Michal Hocko > --- > mm/memcontrol.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 57048a38c75d..e9af606238ab 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6301,8 +6301,8 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, > } > > exit: > - memcg->memory.emin = emin; > - memcg->memory.elow = elow; > + WRITE_ONCE(memcg->memory.emin, emin); > + WRITE_ONCE(memcg->memory.elow, elow); > > if (usage <= emin) > return MEMCG_PROT_MIN; > -- > 2.25.1 -- Michal Hocko SUSE Labs