Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754062Ab3IYH4H (ORCPT ); Wed, 25 Sep 2013 03:56:07 -0400 Received: from hydra.sisk.pl ([212.160.235.94]:56888 "EHLO hydra.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751172Ab3IYH4G (ORCPT ); Wed, 25 Sep 2013 03:56:06 -0400 From: "Rafael J. Wysocki" To: Kyungmin Park Cc: Tejun Heo , Bartlomiej Zolnierkiewicz , Pavel Machek , linux-pm@vger.kernel.org, LKML , Colin Cross Subject: Re: [RFC PATCH] freezer: allow killing of frozen tasks Date: Wed, 25 Sep 2013 10:07:22 +0200 Message-ID: <2084875.Px2m8K6oH7@vostro.rjw.lan> User-Agent: KMail/4.10.5 (Linux/3.11.0+; KDE/4.10.5; x86_64; ; ) In-Reply-To: References: <5917186.DMyAa9ofOj@amdc1032> <7588112.eXrFpITlCh@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 Content-Length: 2113 Lines: 46 On Wednesday, September 25, 2013 02:52:26 PM Kyungmin Park wrote: > On Tue, Aug 20, 2013 at 9:41 PM, Rafael J. Wysocki wrote: > > On Tuesday, August 20, 2013 08:27:27 AM Tejun Heo wrote: > >> 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. > > > > Which might be worth doing anyway to be sure we know what's going on. > > > >> Anyways, we need to ensure that userland task doesn't get stuck deep in the > >> kernel before allowing this. > > > > Agreed. > > Are there any update? we need this feature to kill frozen app easily. > Don't need to thaw app to kill. No updates, but the above pretty much describes what needs to be done. Thanks, Rafael -- 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/