From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id BC9766B01F2 for ; Wed, 31 Mar 2010 02:17:51 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o2V6Hn34007116 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Wed, 31 Mar 2010 15:17:49 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 0F2D945DE86 for ; Wed, 31 Mar 2010 15:17:49 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 4DCE745DE80 for ; Wed, 31 Mar 2010 15:17:46 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 052D9E18001 for ; Wed, 31 Mar 2010 15:17:46 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 505DBE1800E for ; Wed, 31 Mar 2010 15:17:45 +0900 (JST) Date: Wed, 31 Mar 2010 15:13:56 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH] oom killer: break from infinite loop Message-Id: <20100331151356.673c16c0.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <1269447905-5939-1-git-send-email-anfei.zhou@gmail.com> <20100326150805.f5853d1c.akpm@linux-foundation.org> <20100326223356.GA20833@redhat.com> <20100328145528.GA14622@desktop> <20100328162821.GA16765@redhat.com> <20100329140633.GA26464@desktop> <20100330142923.GA10099@desktop> <20100331095714.9137caab.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: David Rientjes Cc: anfei , Oleg Nesterov , Andrew Morton , KOSAKI Motohiro , nishimura@mxp.nes.nec.co.jp, Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "balbir@linux.vnet.ibm.com" List-ID: On Tue, 30 Mar 2010 23:07:08 -0700 (PDT) David Rientjes wrote: > On Wed, 31 Mar 2010, KAMEZAWA Hiroyuki wrote: > > > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > > > index 0cb1ca4..9e89a29 100644 > > > > --- a/mm/oom_kill.c > > > > +++ b/mm/oom_kill.c > > > > @@ -510,8 +510,10 @@ retry: > > > > if (PTR_ERR(p) == -1UL) > > > > goto out; > > > > > > > > - if (!p) > > > > - p = current; > > > > + if (!p) { > > > > + read_unlock(&tasklist_lock); > > > > + panic("Out of memory and no killable processes...\n"); > > > > + } > > > > > > > > if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, > > > > "Memory cgroup out of memory")) > > > > > > > > > > This actually does appear to be necessary but for a different reason: if > > > current is unkillable because it has OOM_DISABLE, for example, then > > > oom_kill_process() will repeatedly fail and mem_cgroup_out_of_memory() > > > will infinitely loop. > > > > > > Kame-san? > > > > > > > When a memcg goes into OOM and it only has unkillable processes (OOM_DISABLE), > > we can do nothing. (we can't panic because container's death != system death.) > > > > Because memcg itself has mutex+waitqueue for mutual execusion of OOM killer, > > I think infinite-loop will not be critical probelm for the whole system. > > > > And, now, memcg has oom-kill-disable + oom-kill-notifier features. > > So, If a memcg goes into OOM and there is no killable process, but oom-kill is > > not disabled by memcg.....it means system admin's mis-configuraton. > > > > He can stop inifite loop by hand, anyway. > > # echo 1 > ..../group_A/memory.oom_control > > > > Then we should be able to do this since current is by definition > unkillable since it was not found in select_bad_process(), right? To me, this patch is acceptable and seems reasnoable. But I didn't joined to memcg development when this check was added and don't know why kill current.. http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=c7ba5c9e8176704bfac0729875fa62798037584d Addinc Balbir to CC. Maybe situation is changed now. Because we can stop inifinite loop (by hand) and there is no rushing oom-kill callers, this change is acceptable. Thanks, -Kame > --- > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -500,12 +500,9 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask) > read_lock(&tasklist_lock); > retry: > p = select_bad_process(&points, limit, mem, CONSTRAINT_NONE, NULL); > - if (PTR_ERR(p) == -1UL) > + if (!p || PTR_ERR(p) == -1UL) > goto out; > > - if (!p) > - p = current; > - > if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, > "Memory cgroup out of memory")) > goto retry; > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org