Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751371Ab3HTMSZ (ORCPT ); Tue, 20 Aug 2013 08:18:25 -0400 Received: from mail-qc0-f170.google.com ([209.85.216.170]:49886 "EHLO mail-qc0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751004Ab3HTMSX (ORCPT ); Tue, 20 Aug 2013 08:18:23 -0400 Date: Tue, 20 Aug 2013 08:18:19 -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: <20130820121819.GA3926@htj.dyndns.org> References: <5917186.DMyAa9ofOj@amdc1032> <4596920.E6jI568rc1@vostro.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4596920.E6jI568rc1@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: 1561 Lines: 37 Hello, On Tue, Aug 20, 2013 at 02:23:32PM +0200, Rafael J. Wysocki wrote: > On Tuesday, August 20, 2013 01:20:03 PM Bartlomiej Zolnierkiewicz wrote: > > Change __refrigerator() to allow SIGKILL signal handling during > > the frozen state (by setting task to a TASK_KILLABLE state instead > > of TASK_UNINTERRUPTIBLE one before entering sleep) and make tasks > > leave __refrigerator() upon receiving such signal. > > > > These changes allow frozen tasks to be killed immediately without > > the need to thaw them first. > > > > Signed-off-by: Bartlomiej Zolnierkiewicz > > Signed-off-by: Kyungmin Park > > Well, it doesn't sound like an entirely bad idea to me, but I'd like to know > what Colin and Tejun (CCed now) think about it. The problem is that we really don't know where each task is frozen in the kernel so don't know what happens after the task leaves the freezer is safe whether it's dying or not. We don't have any rules restricting where a freeze point should be and a task may do any operation between freezer and actual exit. 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. 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/