From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758557AbXGCFov (ORCPT ); Tue, 3 Jul 2007 01:44:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752496AbXGCFoc (ORCPT ); Tue, 3 Jul 2007 01:44:32 -0400 Received: from gate.crashing.org ([63.228.1.57]:49138 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751499AbXGCFoa (ORCPT ); Tue, 3 Jul 2007 01:44:30 -0400 Subject: Re: [PATCH -mm] PM: Prevent frozen user mode helpers from failing the freezing of tasks (rev. 2) From: Benjamin Herrenschmidt To: "Rafael J. Wysocki" Cc: Pavel Machek , Andrew Morton , Nigel Cunningham , Uli Luckas , Oleg Nesterov , linux-kernel@vger.kernel.org In-Reply-To: <200706260027.02396.rjw@sisk.pl> References: <200706252352.24137.rjw@sisk.pl> <20070625215527.GE2051@elf.ucw.cz> <200706260027.02396.rjw@sisk.pl> Content-Type: text/plain Date: Tue, 03 Jul 2007 15:30:46 +1000 Message-Id: <1183440646.10386.66.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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. Ben.