From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756127AbXGCN3d (ORCPT ); Tue, 3 Jul 2007 09:29:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753861AbXGCN30 (ORCPT ); Tue, 3 Jul 2007 09:29:26 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:44752 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753605AbXGCN3Z (ORCPT ); Tue, 3 Jul 2007 09:29:25 -0400 From: "Rafael J. Wysocki" To: Benjamin Herrenschmidt Subject: Re: [PATCH -mm] PM: Prevent frozen user mode helpers from failing the freezing of tasks (rev. 2) Date: Tue, 3 Jul 2007 15:36:58 +0200 User-Agent: KMail/1.9.5 Cc: Pavel Machek , Andrew Morton , Nigel Cunningham , Uli Luckas , Oleg Nesterov , linux-kernel@vger.kernel.org References: <200706252352.24137.rjw@sisk.pl> <1183440646.10386.66.camel@localhost.localdomain> <200707031519.59661.rjw@sisk.pl> In-Reply-To: <200707031519.59661.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707031536.59154.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, 3 July 2007 15:19, Rafael J. Wysocki wrote: > On Tuesday, 3 July 2007 07:30, Benjamin Herrenschmidt wrote: > > On Tue, 2007-06-26 at 00:27 +0200, Rafael J. Wysocki wrote: > > > > > case PM_HIBERNATION_PREPARE: > > > > > case PM_SUSPEND_PREPARE: > > > > > usermodehelper_disabled = 1; > > > > > - return NOTIFY_OK; > > > > > + smp_mb(); > > > > > > > > usermodehelper_disabled should be atomic variable, too, so we don't > > > > have to play these ugly tricks by hand? This should not be > > > > performance-critical, right? > > > > > > Well, I think we'd need to add the barriers anyway. > > > > > > The problem, as far as I understand it, is that the instructions can > > > get > > > reordered if there are no barriers in there. > > > > That seems dodgy either way to me :-) > > > > Just use a spinlock. > > Around wait_for_completion()? I don't think that's a good idea. :-) Sorry, I mistunderstood you (I think). Yes, I could use a spinlock for protecting usermodehelper_disabled, but why would that be better than the current code? Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth