Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751440AbbGIEQN (ORCPT ); Thu, 9 Jul 2015 00:16:13 -0400 Received: from mail113-249.mail.alibaba.com ([205.204.113.249]:59421 "EHLO us-alimail-mta2.hst.scl.en.alidc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750791AbbGIEQE (ORCPT ); Thu, 9 Jul 2015 00:16:04 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R121e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03307;MF=hillf.zj@alibaba-inc.com;PH=DS;RN=6;SR=0; Reply-To: "Hillf Danton" From: "Hillf Danton" To: "David Rientjes" Cc: "Andrew Morton" , "Sergey Senozhatsky" , "Michal Hocko" , "linux-kernel" , Subject: Re: [patch v3 3/3] mm, oom: do not panic for oom kills triggered from sysrq Date: Thu, 09 Jul 2015 12:15:01 +0800 Message-ID: <02e601d0b9fd$d644ec50$82cec4f0$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AdC5/Ip0zZXcsBPuS8emSTuF6glBwA== Content-Language: zh-cn Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2368 Lines: 68 > Sysrq+f is used to kill a process either for debug or when the VM is > otherwise unresponsive. > > It is not intended to trigger a panic when no process may be killed. > > Avoid panicking the system for sysrq+f when no processes are killed. > > Suggested-by: Michal Hocko > Signed-off-by: David Rientjes > --- > v2: no change > v3: fix title per Hillf > > Documentation/sysrq.txt | 3 ++- > mm/oom_kill.c | 7 +++++-- > 2 files changed, 7 insertions(+), 3 deletions(-) > > diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt > --- a/Documentation/sysrq.txt > +++ b/Documentation/sysrq.txt > @@ -75,7 +75,8 @@ On all - write a character to /proc/sysrq-trigger. e.g.: > > 'e' - Send a SIGTERM to all processes, except for init. > > -'f' - Will call oom_kill to kill a memory hog process. > +'f' - Will call the oom killer to kill a memory hog process, but do not > + panic if nothing can be killed. > > 'g' - Used by kgdb (kernel debugger) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -607,6 +607,9 @@ void check_panic_on_oom(struct oom_control *oc, enum oom_constraint constraint, > if (constraint != CONSTRAINT_NONE) > return; > } > + /* Do not panic for oom kills triggered by sysrq */ > + if (oc->order == -1) > + return; > dump_header(oc, NULL, memcg); > panic("Out of memory: %s panic_on_oom is enabled\n", > sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide"); > @@ -686,11 +689,11 @@ bool out_of_memory(struct oom_control *oc) > > p = select_bad_process(oc, &points, totalpages); > /* Found nothing?!?! Either we hang forever, or we panic. */ > - if (!p) { > + if (!p && oc->order != -1) { > dump_header(oc, NULL, NULL); > panic("Out of memory and no killable processes...\n"); > } Given sysctl_panic_on_oom checked, AFAICU there seems no chance for panic, no matter -1 or not. > - if (p != (void *)-1UL) { > + if (p && p != (void *)-1UL) { > oom_kill_process(oc, p, points, totalpages, NULL, > "Out of memory"); > killed = 1; > -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/