From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755483AbaIHXWf (ORCPT ); Mon, 8 Sep 2014 19:22:35 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:64682 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755099AbaIHXWe (ORCPT ); Mon, 8 Sep 2014 19:22:34 -0400 From: "Rafael J. Wysocki" To: Cong Wang Cc: Tejun Heo , LKML , David Rientjes , Michal Hocko , Andrew Morton Subject: Re: [Patch v4 1/2] freezer: check OOM kill while being frozen Date: Tue, 09 Sep 2014 01:42 +0200 Message-ID: <4809128.C6aPga5IjQ@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/3.16.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: References: <1409869842-10807-1-git-send-email-xiyou.wangcong@gmail.com> <1609685.fbsF6EQ3X7@vostro.rjw.lan> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit 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 Monday, September 08, 2014 04:16:15 PM Cong Wang wrote: > On Mon, Sep 8, 2014 at 4:23 PM, Rafael J. Wysocki wrote: > > > > The reason why it matters for the suspend-time freezing is that we freeze tasks > > to take them out of the picture entirely until they are thawed. Therefore we > > can't allow them to go back to the picture just for a while until they are > > killed. Frozen tasks are not supposed to get back to the picture at all. > > > > > Ok, then checking TIF_MEMDIE is unsafe for PM freeze, we should > keep the cgroup_freezing() test to make sure freeze request is from > cgroup not PM. Question got answered. :) Do I think correctly that cgroups freezing and system suspend are mutually exclusive? If not, then this still is problematic. > I will put the following as a comment: > > /* OOM killer may decide to kill this process after it is frozen, > in this case SIGKILL can never be handled, so we should check > TIF_MEMDIE and if it is set, thaw and let SIGKILL kill it. > But for PM freeze, it is not allowed to get out even for a while, > so we have to keep it being frozen. */ > > Let me know if it looks good to you. Well, it reflects the reality, so it's good enough. But please adhere to the coding style rules for comments. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.