From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965319AbcBQOjy (ORCPT ); Wed, 17 Feb 2016 09:39:54 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:44004 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423546AbcBQOjx (ORCPT ); Wed, 17 Feb 2016 09:39:53 -0500 To: mhocko@kernel.org Cc: akpm@linux-foundation.org, rientjes@google.com, mgorman@suse.de, oleg@redhat.com, torvalds@linux-foundation.org, hughd@google.com, andrea@kernel.org, riel@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/6] mm,oom: don't abort on exiting processes when selecting a victim. From: Tetsuo Handa References: <201602171928.GDE00540.SLJMOFFQOHtFVO@I-love.SAKURA.ne.jp> <201602171930.AII18204.FMOSVFQFOJtLOH@I-love.SAKURA.ne.jp> <20160217125418.GF29196@dhcp22.suse.cz> <201602172207.GAG52105.FOtMJOFQOVSFHL@I-love.SAKURA.ne.jp> <20160217140006.GM29196@dhcp22.suse.cz> In-Reply-To: <20160217140006.GM29196@dhcp22.suse.cz> Message-Id: <201602172339.JBJ57868.tSQVJLHMFFOOFO@I-love.SAKURA.ne.jp> X-Mailer: Winbiff [Version 2.51 PL2] X-Accept-Language: ja,en,zh Date: Wed, 17 Feb 2016 23:39:47 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michal Hocko wrote: > On Wed 17-02-16 22:07:31, Tetsuo Handa wrote: > > Michal Hocko wrote: > > > On Wed 17-02-16 19:30:41, Tetsuo Handa wrote: > > > > >From 22bd036766e70f0df38c38f3ecc226e857d20faf Mon Sep 17 00:00:00 2001 > > > > From: Tetsuo Handa > > > > Date: Wed, 17 Feb 2016 16:30:59 +0900 > > > > Subject: [PATCH 2/6] mm,oom: don't abort on exiting processes when selecting a victim. > > > > > > > > Currently, oom_scan_process_thread() returns OOM_SCAN_ABORT when there > > > > is a thread which is exiting. But it is possible that that thread is > > > > blocked at down_read(&mm->mmap_sem) in exit_mm() called from do_exit() > > > > whereas one of threads sharing that memory is doing a GFP_KERNEL > > > > allocation between down_write(&mm->mmap_sem) and up_write(&mm->mmap_sem) > > > > (e.g. mmap()). Under such situation, the OOM killer does not choose a > > > > victim, which results in silent OOM livelock problem. > > > > > > Again, such a thread/task will have fatal_signal_pending and so have > > > access to memory reserves. So the text is slightly misleading imho. > > > Sure if the memory reserves are depleted then we will not move on but > > > then it is not clear whether the current patch helps either. > > > > I don't think so. > > Please see http://lkml.kernel.org/r/201602151958.HCJ48972.FFOFOLMHSQVJtO@I-love.SAKURA.ne.jp . > > I have missed this one. Reading... > > Hmm, so you are not referring to OOM killed task but naturally exiting > thread which is racing with the OOM killer. I guess you have a point > there! Could you update the changelog with the above example and repost > please? > Yes and I resent that patch as v2. I think that the same problem exists for any task_will_free_mem()-based optimizations. Can we eliminate them because these optimized paths are not handled by the OOM reaper which means that we have no means other than "[PATCH 5/6] mm,oom: Re-enable OOM killer using timers." ?