From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932393Ab1KCLPl (ORCPT ); Thu, 3 Nov 2011 07:15:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12304 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753267Ab1KCLPj (ORCPT ); Thu, 3 Nov 2011 07:15:39 -0400 Date: Thu, 3 Nov 2011 07:15:16 -0400 From: Jeff Layton To: "Rafael J. Wysocki" Cc: Oleg Nesterov , Tejun Heo , Steve French , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-cifs@vger.kernel.org, "J. Bruce Fields" , Neil Brown , trond.myklebust@netapp.com, linux-nfs@vger.kernel.org Subject: Re: [RFC PATCH] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too" Message-ID: <20111103071516.79fb42fa@tlielax.poochiereds.net> In-Reply-To: <201111030011.24062.rjw@sisk.pl> References: <20111101041337.39077229@tlielax.poochiereds.net> <20111101215710.GA13803@google.com> <20111102162331.GA31947@redhat.com> <201111030011.24062.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 3 Nov 2011 00:11:23 +0100 "Rafael J. Wysocki" wrote: > On Wednesday, November 02, 2011, Oleg Nesterov wrote: > > Hi, > > > > On 11/01, Tejun Heo wrote: > > > > > > For now, let's go with the count/dont_count. Can you please write up > > > a patch for that? Jeff, does this seem okay to you? > > > > OK, will do in a minute. On top of > > "[PATCH pm] freezer: fix wait_event_freezable/__thaw_task races" > > you sent. (btw, thanks, I forgout about it ;) > > > > Rafael, could you remind why freezer_do_not_count/freezer_count check > > ->mm != NULL ? > > You're asking difficult questions. ;-) > > The intention was to prevent PF_FREEZER_SKIP from having any effect on > kernel threads, IIRC. Anyway, there are only two legitimate users of it > (vfork and apm_ioctl) and in both cases the task in question is user space. > > > The comment says "However, we don't want kernel threads to be frozen", > > but it is not clear anyway. A kernel thread simply shouldn't use this > > interface if it doesn't want to freeze. > > > > And in any case, PF_KTHREAD looks better if we really need to filter > > out the kernel threads. > > PF_FREEZER_SKIP was introduced specifically with vfork in mind and I'm not > sure if it's a good idea to re-use it for something else (at least not for > something entirely obvious). > FWIW, wrapping wait_event_killable in freezer_do_not_count/freezer_count seems to work. The machine suspends consistently with it. It sounds like Rafael has concerns about this scheme however, so I'll let you guys argue this out :) Once you tell me the right scheme to use, I'll be happy to fix up cifs and nfs to use it. Thanks, -- Jeff Layton