Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757300AbZDFT6f (ORCPT ); Mon, 6 Apr 2009 15:58:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754804AbZDFT6Y (ORCPT ); Mon, 6 Apr 2009 15:58:24 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:49446 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752899AbZDFT6X (ORCPT ); Mon, 6 Apr 2009 15:58:23 -0400 From: "Rafael J. Wysocki" To: Alan Stern , Peter Zijlstra Subject: Re: [linux-pm] pm-hibernate : possible circular locking dependency detected Date: Mon, 6 Apr 2009 21:58:10 +0200 User-Agent: KMail/1.11.2 (Linux/2.6.29-rjw; KDE/4.2.2; x86_64; ; ) Cc: Gautham R Shenoy , Rusty Russell , Linux Kernel List , "Linux-pm mailing list" , Ingo Molnar , Andrew Morton 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: <200904062158.11245.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1324 Lines: 31 On Monday 06 April 2009, Alan Stern wrote: > On Mon, 6 Apr 2009, Gautham R Shenoy wrote: > > > > If I understand correctly it isn't really a deadlock scenario, but it > > > is a lockdep violation. The violation is: > > > > > > The pci_device_probe() path 2) proves that dpm_list_mtx [4] can > > > be acquired while cpu_hotplug.lock [3] is held; > > > > > > The hibernate() path 3) proves that cpu_hotplug.lock [3] can be > > > acquired while dpm_list_mtx [4] is held. > > > > > > The two pathways cannot run simultaneously (and hence cannot deadlock) > > > because the prepare() stage of hibernation is supposed to stop all > > > device probing. But lockdep will still report a problem. > > > > Thanks for clarifying this Alan. I guess it boils down to teaching > > lockdep about this false-positive. > > Or else changing the code somehow to avoid the violation completely. > But I have no idea how... And AFAIK, teaching lockdep about special > cases like this is not so easy to do. Yeah, I've just wanted to ask about that. Peter, how can we do it? 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/