From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751083AbWFLQle (ORCPT ); Mon, 12 Jun 2006 12:41:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751227AbWFLQle (ORCPT ); Mon, 12 Jun 2006 12:41:34 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:56369 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S1751083AbWFLQld (ORCPT ); Mon, 12 Jun 2006 12:41:33 -0400 Date: Mon, 12 Jun 2006 18:41:53 +0200 From: Jens Axboe To: Arjan van de Ven Cc: Laurent Riffard , Kernel development list , petero2@telia.com Subject: Re: 2.6.17-rc6-mm1/pktcdvd - BUG: possible circular locking Message-ID: <20060612164152.GP4420@suse.de> References: <448875D1.5080905@free.fr> <448D84C0.1070400@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <448D84C0.1070400@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 12 2006, Arjan van de Ven wrote: > Laurent Riffard wrote: > >Hello, > > > >This BUG happened while pktcdvd service was starting. > >Basically, the 2 following commands were issued: > >- modprobe ptkcdvd > >- pktsetup dvd /dev/dvd > > This appears to be a real bug: > > A normal pkt dvd block dev open takes the > bdev_mutex in the regular block device open path, which takes > ctl_mutex in the pkt_open function which gets called then from > the block layer. > > HOWEVER the IOCTL path does it the other way around: > > mutex_lock(&ctl_mutex); > ret = pkt_setup_dev(&ctrl_cmd); > mutex_unlock(&ctl_mutex); > > where pkt_setup_dev in term calls pkt_new_dev which > calls blkdev_get(), which takes the bdev_mutex. > > Looks very much like a AB-BA deadlock to me... I'd say you are right, however I haven't touched that code since 2.5 I think - CC'ing Peter for a fix! -- Jens Axboe