From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760666AbcAKPSj (ORCPT ); Mon, 11 Jan 2016 10:18:39 -0500 Received: from mail-wm0-f50.google.com ([74.125.82.50]:35311 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759093AbcAKPSi (ORCPT ); Mon, 11 Jan 2016 10:18:38 -0500 Date: Mon, 11 Jan 2016 16:18:35 +0100 From: Michal Hocko To: Tetsuo Handa Cc: rientjes@google.com, akpm@linux-foundation.org, mgorman@suse.de, torvalds@linux-foundation.org, oleg@redhat.com, hughd@google.com, andrea@kernel.org, riel@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Message-ID: <20160111151835.GH27317@dhcp22.suse.cz> References: <201512292258.ABF87505.OFOSJLHMFVOQFt@I-love.SAKURA.ne.jp> <20160107091512.GB27868@dhcp22.suse.cz> <201601072231.DGG78695.OOFVLHJFFQOStM@I-love.SAKURA.ne.jp> <20160107145841.GN27868@dhcp22.suse.cz> <201601080038.CIF04698.VFJHSOQLOFFMOt@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201601080038.CIF04698.VFJHSOQLOFFMOt@I-love.SAKURA.ne.jp> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 08-01-16 00:38:43, Tetsuo Handa wrote: > Michal Hocko wrote: > > @@ -333,6 +333,14 @@ static struct task_struct *select_bad_process(struct oom_control *oc, > > if (points == chosen_points && thread_group_leader(chosen)) > > continue; > > > > + /* > > + * If the current major task is already ooom killed and this > > + * is sysrq+f request then we rather choose somebody else > > + * because the current oom victim might be stuck. > > + */ > > + if (is_sysrq_oom(sc) && test_tsk_thread_flag(p, TIF_MEMDIE)) > > + continue; > > + > > chosen = p; > > chosen_points = points; > > } > > Do we want to require SysRq-f for each thread in a process? > If g has 1024 p, dump_tasks() will do > > pr_info("[%5d] %5d %5d %8lu %8lu %7ld %7ld %8lu %5hd %s\n", > > for 1024 times? I think one SysRq-f per one process is sufficient. I am not following you here. If we kill the process the whole process group (aka all threads) will get killed which ever thread we happen to send the sigkill to. > How can we guarantee that find_lock_task_mm() from oom_kill_process() > chooses !TIF_MEMDIE thread when try_to_sacrifice_child() somehow chose > !TIF_MEMDIE thread? I think choosing !TIF_MEMDIE thread at > find_lock_task_mm() is the simplest way. find_lock_task_mm chosing TIF_MEMDIE thread shouldn't change anything because the whole thread group will go down anyway. If you want to guarantee that the sysrq+f never choses a task which has a TIF_MEMDIE thread then we would have to check for fatal_signal_pending as well AFAIU. Fiddling with find find_lock_task_mm will not help you though unless I am missing something. -- Michal Hocko SUSE Labs