From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: pm-hibernate : possible circular locking dependency detected Date: Mon, 6 Apr 2009 21:58:10 +0200 Message-ID: <200904062158.11245.rjw@sisk.pl> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Alan Stern , Peter Zijlstra Cc: Rusty Russell , Linux Kernel List , Ingo Molnar , Andrew Morton , Linux-pm mailing list List-Id: linux-pm@vger.kernel.org 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