From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752338AbcGSX2D (ORCPT ); Tue, 19 Jul 2016 19:28:03 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:49056 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751827AbcGSX2B (ORCPT ); Tue, 19 Jul 2016 19:28:01 -0400 Date: Tue, 19 Jul 2016 16:27:59 -0700 From: Andrew Morton To: Michal Hocko Cc: linux-mm@kvack.org, Tetsuo Handa , David Rientjes , Oleg Nesterov , Vladimir Davydov , LKML Subject: Re: [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init Message-Id: <20160719162759.e391c685db7a8de30b79320c@linux-foundation.org> In-Reply-To: <20160719120538.GE9490@dhcp22.suse.cz> References: <1466426628-15074-1-git-send-email-mhocko@kernel.org> <1466426628-15074-11-git-send-email-mhocko@kernel.org> <20160719120538.GE9490@dhcp22.suse.cz> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 19 Jul 2016 14:05:39 +0200 Michal Hocko wrote: > > After this patch we should guarantee a forward progress for the OOM > > killer even when the selected victim is sharing memory with a kernel > > thread or global init. > > Could you replace the last two paragraphs with the following. Tetsuo > didn't like the guarantee mentioned there because that is a too strong > statement as find_lock_task_mm might not find any mm and so we still > could end up looping on the oom victim if it gets stuck somewhere in > __mmput. This particular patch didn't aim at closing that case. Plugging > that hole is planned later after the next upcoming merge window closes. > > " > In order to help a forward progress for the OOM killer, make sure > that this really rare cases will not get into the way and hide > the mm from the oom killer by setting MMF_OOM_REAPED flag for it. > oom_scan_process_thread will ignore any TIF_MEMDIE task if it has > MMF_OOM_REAPED flag set to catch these oom victims. > > After this patch we should guarantee a forward progress for the OOM > killer even when the selected victim is sharing memory with a kernel > thread or global init as long as the victims mm is still alive. > " I tweaked it a bit: : In order to help forward progress for the OOM killer, make sure that : this really rare case will not get in the way - we do this by hiding : the mm from the oom killer by setting MMF_OOM_REAPED flag for it. : oom_scan_process_thread will ignore any TIF_MEMDIE task if it has : MMF_OOM_REAPED flag set to catch these oom victims. : : After this patch we should guarantee forward progress for the OOM : killer even when the selected victim is sharing memory with a kernel : thread or global init as long as the victims mm is still alive.