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=-5.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 7C106C433E1 for ; Fri, 21 Aug 2020 16:38:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56CE1207BB for ; Fri, 21 Aug 2020 16:38:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MO+q2Z3N" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728461AbgHUQiU (ORCPT ); Fri, 21 Aug 2020 12:38:20 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:37459 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728611AbgHUQho (ORCPT ); Fri, 21 Aug 2020 12:37:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1598027862; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=0lJhV0AuRAshzZDQ8A0+XwDhVR+Tf/PekK/bov5/xP8=; b=MO+q2Z3NicsYNUsIYUuIS2yCC8MijqA/jFkmZj8DvBvGuDmJbUcDZUU2nSGMGG7bNTD723 1grcshvYYh5x7q+ZdHsVsgjC/hf0cO6DnyLoi4t+4YgrWogimOAEbo0qpHfUeBQCpw8elM /p3mVw1P423aO62Wa7X2RMPiKDi5+7I= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-515-I75JHwW-NbqN86TNKQBV8Q-1; Fri, 21 Aug 2020 12:37:41 -0400 X-MC-Unique: I75JHwW-NbqN86TNKQBV8Q-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 837A780733B; Fri, 21 Aug 2020 16:37:36 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.15]) by smtp.corp.redhat.com (Postfix) with SMTP id 5BE651014186; Fri, 21 Aug 2020 16:37:26 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 21 Aug 2020 18:37:36 +0200 (CEST) Date: Fri, 21 Aug 2020 18:37:25 +0200 From: Oleg Nesterov To: Suren Baghdasaryan 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 Subject: Re: [PATCH 1/1] mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary Message-ID: <20200821163724.GC19445@redhat.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > 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. Oleg.