From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753056AbaIOA5H (ORCPT ); Sun, 14 Sep 2014 20:57:07 -0400 Received: from mail-pa0-f48.google.com ([209.85.220.48]:38994 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752974AbaIOA5D (ORCPT ); Sun, 14 Sep 2014 20:57:03 -0400 Date: Mon, 15 Sep 2014 09:56:57 +0900 From: Tejun Heo To: "Rafael J. Wysocki" Cc: Michal Hocko , Cong Wang , LKML , David Rientjes , Andrew Morton Subject: Re: [Patch v4 1/2] freezer: check OOM kill while being frozen Message-ID: <20140915005657.GA11267@mtj.dyndns.org> References: <1409869842-10807-1-git-send-email-xiyou.wangcong@gmail.com> <20140911163004.GN22042@dhcp22.suse.cz> <20140912235935.GB28183@mtj.dyndns.org> <1527959.PBej7RR7ig@vostro.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1527959.PBej7RR7ig@vostro.rjw.lan> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Sep 14, 2014 at 06:43:31PM +0200, Rafael J. Wysocki wrote: > On Saturday, September 13, 2014 08:59:35 AM Tejun Heo wrote: > > Doesn't this mean that if PM freezing and OOM killing race each other, > > the system may hang? Driver PM operation may try to allocate memory > > -> triggers OOM -> OOM killer selects an already frozen task -> > > nothing happens. I wonder whether OOM killing and PM operations > > should be mutually exclusive at a higher level. e.g. make OOM killing > > always override freezing but let hibernation abort operation before > > taking snapshot if OOM killing has happened since the beginning of the > > PM operation. > > As Michal noted, we do oom_killer_disable() in freeze_processes(), so the > scenario above cannot actually happen to my eyes. Or am I missing anything? Ah, okay, that's better but it doesn't seem enough. It does prevent new invocations of the oom killer but doesn't do anything if oom killing is already in progress. If we do block out oom killing properly across PM freeze/thaw, it shoud be fine. Thanks. -- tejun