Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751415Ab3HTM1d (ORCPT ); Tue, 20 Aug 2013 08:27:33 -0400 Received: from mail-qc0-f180.google.com ([209.85.216.180]:47087 "EHLO mail-qc0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751366Ab3HTM1b (ORCPT ); Tue, 20 Aug 2013 08:27:31 -0400 Date: Tue, 20 Aug 2013 08:27:27 -0400 From: Tejun Heo To: "Rafael J. Wysocki" Cc: Bartlomiej Zolnierkiewicz , Pavel Machek , linux-pm@vger.kernel.org, Kyungmin Park , LKML , Colin Cross Subject: Re: [RFC PATCH] freezer: allow killing of frozen tasks Message-ID: <20130820122727.GC3926@htj.dyndns.org> References: <5917186.DMyAa9ofOj@amdc1032> <37238430.gCktWD5jr4@vostro.rjw.lan> <20130820122200.GB3926@htj.dyndns.org> <7346644.tueXegsfXu@vostro.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7346644.tueXegsfXu@vostro.rjw.lan> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1521 Lines: 34 On Tue, Aug 20, 2013 at 02:34:14PM +0200, Rafael J. Wysocki wrote: > On Tuesday, August 20, 2013 08:22:00 AM Tejun Heo wrote: > > On Tue, Aug 20, 2013 at 02:30:18PM +0200, Rafael J. Wysocki wrote: > > > > So, I don't think we can simply turn TASK_UNITERRUPTIBLE to > > > > TASK_KILLABLE at this point. We really need to strictly define where > > > > a task can freeze before being able to do anything like this. > > > > > > But we could do that for user space tasks I suppose? > > > > Even for userland tasks, we don't know where the task is stuck at. I > > think there are enough freeze points in the kernel which are in the > > middle of something which can be used by userland tasks excuting some > > syscall. We need to collect all those sites into well defined trap > > points before doing this. > > OK, thanks! I scanned through try_to_freeze() users and it seems like we don't have that many which can be hit by userland tasks. I think it should be doable to audit all the users, remove the ones which can be invoked by userland and make try_to_freeze() whine loudly if it's running off a userland task except from well-defined spots. Anyways, we need to ensure that userland task doesn't get stuck deep in the kernel before allowing this. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/