From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f170.google.com (mail-pd0-f170.google.com [209.85.192.170]) by kanga.kvack.org (Postfix) with ESMTP id C618C6B0038 for ; Thu, 9 Jul 2015 00:15:26 -0400 (EDT) Received: by pdbep18 with SMTP id ep18so157276666pdb.1 for ; Wed, 08 Jul 2015 21:15:26 -0700 (PDT) Received: from out11.biz.mail.alibaba.com (out114-135.biz.mail.alibaba.com. [205.204.114.135]) by mx.google.com with ESMTP id nh9si7159780pdb.77.2015.07.08.21.15.24 for ; Wed, 08 Jul 2015 21:15:25 -0700 (PDT) Reply-To: "Hillf Danton" From: "Hillf Danton" 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 Content-Language: zh-cn Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Andrew Morton , Sergey Senozhatsky , Michal Hocko , linux-kernel , linux-mm@kvack.org > 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, 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