From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161742AbcFHGWY (ORCPT ); Wed, 8 Jun 2016 02:22:24 -0400 Received: from mail-wm0-f51.google.com ([74.125.82.51]:33445 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752272AbcFHGWX (ORCPT ); Wed, 8 Jun 2016 02:22:23 -0400 Date: Wed, 8 Jun 2016 08:22:20 +0200 From: Michal Hocko To: David Rientjes Cc: Oleg Nesterov , linux-mm@kvack.org, Tetsuo Handa , Vladimir Davydov , Andrew Morton , LKML Subject: Re: [PATCH 06/10] mm, oom: kill all tasks sharing the mm Message-ID: <20160608062219.GA22570@dhcp22.suse.cz> References: <1464945404-30157-1-git-send-email-mhocko@kernel.org> <1464945404-30157-7-git-send-email-mhocko@kernel.org> <20160606232007.GA624@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 07-06-16 15:15:37, David Rientjes wrote: > On Tue, 7 Jun 2016, Oleg Nesterov wrote: > > > On 06/06, David Rientjes wrote: > > > > > > > There is a potential race where we kill the oom disabled task which is > > > > highly unlikely but possible. It would happen if __set_oom_adj raced > > > > with select_bad_process and then it is OK to consider the old value or > > > > with fork when it should be acceptable as well. > > > > Let's add a little note to the log so that people would tell us that > > > > this really happens in the real life and it matters. > > > > > > > > > > We cannot kill oom disabled processes at all, little race or otherwise. > > > > But this change doesn't really make it worse? > > > > Why is the patch asking users to report oom killing of a process that > raced with setting /proc/pid/oom_score_adj to OOM_SCORE_ADJ_MIN? What is > possibly actionable about it? Well, the primary point is to know whether such races happen in the real loads and whether they actually matter. If yes we can harden the locking or come up with a less racy solutions. -- Michal Hocko SUSE Labs