From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751172AbaIJFVI (ORCPT ); Wed, 10 Sep 2014 01:21:08 -0400 Received: from mail-ob0-f171.google.com ([209.85.214.171]:44507 "EHLO mail-ob0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750765AbaIJFVG (ORCPT ); Wed, 10 Sep 2014 01:21:06 -0400 MIME-Version: 1.0 In-Reply-To: <5074996.Ni2JIb7nJr@vostro.rjw.lan> References: <1409869842-10807-1-git-send-email-xiyou.wangcong@gmail.com> <20140909151655.GB4851@dhcp22.suse.cz> <20140909152336.GB8890@mtj.dyndns.org> <5074996.Ni2JIb7nJr@vostro.rjw.lan> Date: Tue, 9 Sep 2014 22:21:05 -0700 Message-ID: Subject: Re: [Patch v4 1/2] freezer: check OOM kill while being frozen From: Cong Wang To: "Rafael J. Wysocki" Cc: Tejun Heo , Michal Hocko , LKML , David Rientjes , Andrew Morton Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 9, 2014 at 1:48 PM, Rafael J. Wysocki wrote: > On Wednesday, September 10, 2014 12:23:36 AM Tejun Heo wrote: >> On Tue, Sep 09, 2014 at 05:16:55PM +0200, Michal Hocko wrote: >> > But OOM killer doesn't kill kernel threads as they do not own any >> > memory. So the check should be safe, no? >> >> Even for userland tasks, try_to_freeze() can currently be anywhere in >> the kernel. The frequently used ones are few but there are some odd >> ones out, and, again, there's nothing enforcing any structure on >> try_to_freeze() usage. The other thing is that we may do quite a bit >> during exiting including allocating memory. Are those safe for system >> PM? Rafael, what exactly are the rules for PM? What shouldn't >> change? > > We can't make any assumptions regarding the availability of any devices. > That is, whatever can end up in device access may potentially fail. > So we still have to rule out PM freeze, right? I am thinking about adding a new task flag or adding a new parameter to __refrigerator() to distinguish PM freeze with cgroup freeze. Will try to code tomorrow. Thanks!