From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161315AbWGNW3T (ORCPT ); Fri, 14 Jul 2006 18:29:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161316AbWGNW3T (ORCPT ); Fri, 14 Jul 2006 18:29:19 -0400 Received: from a222036.upc-a.chello.nl ([62.163.222.36]:45539 "EHLO laptopd505.fenrus.org") by vger.kernel.org with ESMTP id S1161315AbWGNW3T (ORCPT ); Fri, 14 Jul 2006 18:29:19 -0400 Subject: Re: 2.6.17-rc6-mm1/pktcdvd - BUG: possible circular locking From: Arjan van de Ven To: Peter Osterlund Cc: Laurent Riffard , Kernel development list , axboe@suse.de In-Reply-To: References: <448875D1.5080905@free.fr> <448D84C0.1070400@linux.intel.com> <1151000451.3120.56.camel@laptopd505.fenrus.org> <1152884770.3159.37.camel@laptopd505.fenrus.org> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Sat, 15 Jul 2006 00:29:13 +0200 Message-Id: <1152916153.3159.51.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > In the first call chain, do_open -> pkt_open, the bd_mutex object that > is being locked corresponds to a pktcdvd block device, because those > are the only devices that have their open method set to pkt_open. > > In the second call chain, pkt_ctl_ioctl -> pkt_new_dev -> do_open, the > bd_mutex object that is being locked *does not* correspond to a > pktcdvd block device, because pkt_new_dev will bail out with a "Can't > chain pktcdvd devices" error if you call it with "dev" set to a > pktcdvd device. > > Therefore, there is no AB-BA deadlock possibility. The locking > dependencies are A -> B and B -> A', where it is known that A, B and > A' are all different. > > So the claim from the lockdep code, "BUG: possible circular locking > deadlock detected!", is a false alarm. ok I'll try to find a annotation for that that works