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=-7.0 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 CBE29C0044D for ; Mon, 16 Mar 2020 14:59:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8D4AA2071C for ; Mon, 16 Mar 2020 14:59:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8D4AA2071C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 42C306B0007; Mon, 16 Mar 2020 10:59:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 402886B0008; Mon, 16 Mar 2020 10:59:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3178F6B000A; Mon, 16 Mar 2020 10:59:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0168.hostedemail.com [216.40.44.168]) by kanga.kvack.org (Postfix) with ESMTP id 153256B0007 for ; Mon, 16 Mar 2020 10:59:27 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 8592ADB41 for ; Mon, 16 Mar 2020 14:59:26 +0000 (UTC) X-FDA: 76601533932.25.crime36_6f7f9c4be322c X-HE-Tag: crime36_6f7f9c4be322c X-Filterd-Recvd-Size: 3775 Received: from mail-wm1-f65.google.com (mail-wm1-f65.google.com [209.85.128.65]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Mon, 16 Mar 2020 14:59:26 +0000 (UTC) Received: by mail-wm1-f65.google.com with SMTP id 11so18007724wmo.2 for ; Mon, 16 Mar 2020 07:59:26 -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=MD6tLQX2Kknuy7OpI+rU9xXnyKVYqhOFvblKx45lxPJks+TQ4uyJgvAmth4txycui5 o/y7Ba5CZYNBshB6AKyo7MO1QjwhoB/UVB0qHejSuXACADLUghpwecWG/kWhRulv0Ett S2pWUUHMJwEWYQzbpZHGbfLNAAaPyt063AkNNvO/AsrM9K/R2+eT/MarSO+tj095RxDj THcwAo1cWH4CHEkUM4bdPVJA1VmoeCjnTXML9mKUumAa2of61C21K6+Qqxr0RHrSTEkK Xfwek2/Wq7zxyW4BNocJibF8fksh6mPF1x3XHMGVafh0jKHBKt4J1nb9Id9a2SVMRqLy IpOg== X-Gm-Message-State: ANhLgQ3jmX5AK/GWYMCKOzviVw4tM6yZHlHWy2aV1meeG2c+01SSMlb2 yCjSqFaT0NZJZOdNYUb3wSA= 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: 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 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