From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754236AbXDWVS2 (ORCPT ); Mon, 23 Apr 2007 17:18:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754238AbXDWVS2 (ORCPT ); Mon, 23 Apr 2007 17:18:28 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:52264 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754231AbXDWVS1 (ORCPT ); Mon, 23 Apr 2007 17:18:27 -0400 Date: Tue, 24 Apr 2007 02:46:16 +0530 From: Gautham R Shenoy To: Oleg Nesterov Cc: "Rafael J. Wysocki" , Andrew Morton , Ingo Molnar , linux-kernel@vger.kernel.org, vatsa@in.ibm.com, paulmck@us.ibm.com, pavel@ucw.cz Subject: Re: [RFC][PATCH -mm 3/3] freezer: Fix problem with kthread_stop Message-ID: <20070423211616.GA27214@in.ibm.com> Reply-To: ego@in.ibm.com References: <20070419120131.GB13435@in.ibm.com> <200704222141.00680.rjw@sisk.pl> <20070423123558.GC25144@in.ibm.com> <200704232155.36820.rjw@sisk.pl> <20070423204637.GA441@tv-sign.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070423204637.GA441@tv-sign.ru> User-Agent: Mutt/1.5.12-2006-07-14 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 24, 2007 at 12:46:37AM +0400, Oleg Nesterov wrote: > On 04/23, Rafael J. Wysocki wrote: > > > > On Monday, 23 April 2007 14:35, Gautham R Shenoy wrote: > > > > + if (!freezer_should_exempt(current)) { > > > task_lock(k); > > > > + /* We are freezable, so we must make sure that the thread being > > > > + * stopped is not frozen and will not be frozen until it dies > > > > + */ > > > > + freezer_exempt(k); > > > > + if (frozen(k)) > > > > + clear_frozen_flag(k); > > > task_unlock(k); > > > > + } > > > > Yes, that's correct. We need to take task_lock() to avoid the race with > > refrigerator(). > > Even if we use thaw_task() ? I don't think so. As you correctly pointed out, thaw_task() is race free w.r.t the refrigerator(). > > Even if I am wrong, I think we should not use task_lock() for the freezing > related code, except in freezer.[ch] > > Note also that without CONFIG_FREEZER freezer_should_exempt() == 0, so we > will do unneeded task_lock/task_unlock. > > Oleg. > Thanks and Regards gautham. -- Gautham R Shenoy Linux Technology Center IBM India. "Freedom comes with a price tag of responsibility, which is still a bargain, because Freedom is priceless!"