Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752704AbXLYQCM (ORCPT ); Tue, 25 Dec 2007 11:02:12 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751000AbXLYQCA (ORCPT ); Tue, 25 Dec 2007 11:02:00 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:35160 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750752AbXLYQB7 (ORCPT ); Tue, 25 Dec 2007 11:01:59 -0500 From: "Rafael J. Wysocki" To: Alan Stern Subject: Re: [PATCH 0/3] PM: Do not destroy/create devices while suspended Date: Tue, 25 Dec 2007 17:21:41 +0100 User-Agent: KMail/1.9.6 (enterprise 20070904.708012) Cc: pm list , ACPI Devel Maling List , Andrew Morton , Len Brown , LKML , Pavel Machek , Ingo Molnar References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200712251721.42233.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1987 Lines: 43 On Monday, 24 of December 2007, Alan Stern wrote: > On Mon, 24 Dec 2007, Rafael J. Wysocki wrote: > > > Hi, > > > > Some device drivers register CPU hotplug notifiers and use them to destroy > > device objects when removing the corresponding CPUs and to create these objects > > when adding the CPUs back. > > > > Unfortunately, this is not the right thing to do during suspend/hibernation, > > since in that cases the CPU hotplug notifiers are called after suspending > > devices and before resuming them, so the operations in question are carried > > out on the objects representing suspended devices which shouldn't be > > unregistered behing the PM core's back. Although right now it usually doesn't > > lead to any practical complications, it will predictably deadlock if > > gregkh-driver-pm-acquire-device-locks-prior-to-suspending.patch is applied. > > > > The solution is to prevent drivers from removing/adding devices from within > > CPU hotplug notifiers during suspend/hibernation using the FROZEN bit > > in the notifier's action argument. The following three patches modify the > > MSR, x86-64 MCE and cpuid drivers along these lines. > > Do we need to worry about the possibility that when the system wakes up > from hibernation, the set of usable CPUs might be smaller than it was > beforehand? This is possible in error conditions. > Is any special handling needed for this, or is it already accounted for? Hm, well. The cleanest thing would be to allow the drivers to remove the device objects on CPU_UP_CANCELED_FROZEN, which means that we weren't able to bring the CPU up during a resume, but still that will deadlock with gregkh-driver-pm-acquire-device-locks-prior-to-suspending.patch. Greetings, 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/