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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 027C8C433DF for ; Fri, 21 Aug 2020 17:22:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BA06920738 for ; Fri, 21 Aug 2020 17:22:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="fsv4g5/t" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA06920738 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 4B7AF8D0050; Fri, 21 Aug 2020 13:22:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 467C88D0002; Fri, 21 Aug 2020 13:22:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 37EE28D0050; Fri, 21 Aug 2020 13:22:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0143.hostedemail.com [216.40.44.143]) by kanga.kvack.org (Postfix) with ESMTP id 2314E8D0002 for ; Fri, 21 Aug 2020 13:22:48 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id CA6373649 for ; Fri, 21 Aug 2020 17:22:47 +0000 (UTC) X-FDA: 77175245574.19.jewel53_5309f022703b Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin19.hostedemail.com (Postfix) with ESMTP id 77DAB1AD1B7 for ; Fri, 21 Aug 2020 17:22:47 +0000 (UTC) X-HE-Tag: jewel53_5309f022703b X-Filterd-Recvd-Size: 4961 Received: from mail-vs1-f68.google.com (mail-vs1-f68.google.com [209.85.217.68]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Fri, 21 Aug 2020 17:22:47 +0000 (UTC) Received: by mail-vs1-f68.google.com with SMTP id b26so1189456vsa.13 for ; Fri, 21 Aug 2020 10:22:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=rDqVNDY5Q+RZDqESGD0TGY14TPQ/cJSVcY4W2ZTOurU=; b=fsv4g5/tYJjOZyeNAid6KP6IC/d+32IDs1B84c2++eXQf89w47tOGpLE8FXrjFv3/Y jnlLa9noNsJIa4Elln1YeI9aod0vrZLaR52LTJzo0JMk3SyylMuj93Kk0KjI7YAs+pnz RL/cnKuZ9cc9suLnmxGsHHPb9lBpp80bJcJI1TshbZV3bZKHYiyib1+xgGH3sIF6p027 kcTzZXQWPS+rYqmCxqRyzoKXiqJJfRcBxzq5Lx96V6fIR2YgRaFbyP9e0hkDx4GijMAG qitSwMCHtXfcd4M4frAsJPIHOR6nLv2y9mJFaw4VrOy3QbWhfod2LsF52cyBWN1Flbtf vnDA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=rDqVNDY5Q+RZDqESGD0TGY14TPQ/cJSVcY4W2ZTOurU=; b=fY8Cd72d2/ogGtjCkm0TJH2cFZxqlbfcvwG8k0Q3kAG3WsEbUcbGXTXP4ds0/PBUIa 5JqiY2A0piLR1ELJuGoFK+UVRdYMCn0gHnKTd/GgAqRp5TvQEV+bEdUhvAtJ/2KALl/Y sQwm3bETUIIwAJWmiIy1SpDpt7UzcOg/DhU5WOpX1rWvflkIC6LFqrLcVQuwm3P3ADF9 iKL64YHtlpiKdooAaG0lACAt6Rg5bvVLCBBrrlqTIGCjnFrSQLOHskPVonjMnBkOL3Wo qrYkIpAfpYmyUvvFIeg+EQ79ATbUWwzlW22vv3bLY/3LGzaXPdAb8WjjIHrhhFeXUx3a l1Iw== X-Gm-Message-State: AOAM530di10LCN24Z2KStTpDPy/5JHO5sqK+uemERfG4HQBWaAtK1U+8 PGsQYGF95YgEDvgBIu+vEV4ZEPCEOfVq6Nd4MwDtkA== X-Google-Smtp-Source: ABdhPJzA6appk8Xhd4tm4AjN6izo2oLrkOILpz+oGjpaon/Hiqu27vcPQ3jAQ/sCmSWKBd2jYGp5pyBMjq8/f5OPO+c= X-Received: by 2002:a05:6102:189:: with SMTP id r9mr2590828vsq.239.1598030565992; Fri, 21 Aug 2020 10:22:45 -0700 (PDT) MIME-Version: 1.0 References: <20200820140054.fdkbotd4tgfrqpe6@wittgenstein> <637ab0e7-e686-0c94-753b-b97d24bb8232@i-love.sakura.ne.jp> <87k0xtv0d4.fsf@x220.int.ebiederm.org> <20200820162645.GP5033@dhcp22.suse.cz> <87r1s0txxe.fsf@x220.int.ebiederm.org> <20200821111558.GG4546@redhat.com> <20200821163724.GC19445@redhat.com> In-Reply-To: <20200821163724.GC19445@redhat.com> From: Suren Baghdasaryan Date: Fri, 21 Aug 2020 10:22:34 -0700 Message-ID: Subject: Re: [PATCH 1/1] mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary To: Oleg Nesterov Cc: "Eric W. Biederman" , Michal Hocko , Tetsuo Handa , Christian Brauner , Tim Murray , mingo@kernel.org, Peter Zijlstra , Thomas Gleixner , esyr@redhat.com, christian@kellner.me, areber@redhat.com, Shakeel Butt , cyphar@cyphar.com, adobriyan@gmail.com, Andrew Morton , gladkov.alexey@gmail.com, Michel Lespinasse , daniel.m.jordan@oracle.com, avagin@gmail.com, bernd.edlinger@hotmail.de, John Johansen , laoar.shao@gmail.com, Minchan Kim , kernel-team , LKML , linux-fsdevel@vger.kernel.org, linux-mm Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 77DAB1AD1B7 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 Fri, Aug 21, 2020 at 9:37 AM Oleg Nesterov wrote: > > again, don't really understand... > > On 08/21, Suren Baghdasaryan wrote: > > > > Actually, reviewing again and considering where list_add_tail_rcu is > > happening, maybe the race with clone(CLONE_VM) does not introduce > > false negatives. > > I think it does... Whatever we check, mm_users or MMF_PROC_SHARED, > the task can do clone(CLONE_VM) right after the check. Ah, yes of course. I missed this same just like in the original patch. > > > However a false negative I think will happen when a > > task shares mm with another task and also has an additional thread. > > Shared mm will increment mm_users without adding to signal->live > > Yes, > > > and > > the additional thread will advance signal->live without adding to > > mm_users. > > No, please note that CLONE_THREAD requires CLONE_VM. My fault. Forgot that CLONE_VM means "share VM" and not "dup VM". Need some coffee. Thanks Oleg! > > Oleg. >