Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752930AbXLXPvY (ORCPT ); Mon, 24 Dec 2007 10:51:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750934AbXLXPvR (ORCPT ); Mon, 24 Dec 2007 10:51:17 -0500 Received: from netrider.rowland.org ([192.131.102.5]:3724 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750779AbXLXPvR (ORCPT ); Mon, 24 Dec 2007 10:51:17 -0500 Date: Mon, 24 Dec 2007 10:51:15 -0500 (EST) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: "Rafael J. Wysocki" cc: pm list , ACPI Devel Maling List , Andrew Morton , Len Brown , LKML , Pavel Machek , Ingo Molnar Subject: Re: [PATCH 0/3] PM: Do not destroy/create devices while suspended In-Reply-To: <200712240155.14765.rjw@sisk.pl> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1556 Lines: 33 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? Is any special handling needed for this, or is it already accounted for? Alan Stern -- 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/