From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: Re: [BUG] Probably lockdep bug Re: circular locking, mirred, 2.6.24.2 Date: Thu, 6 Mar 2008 09:41:57 +0000 Message-ID: <20080306094156.GA3954@ff.dom.local> References: <20080305103935.M76165@visp.net.lb> <20080305135448.GA4636@ff.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org To: Denys Fedoryshchenko Return-path: Received: from ug-out-1314.google.com ([66.249.92.168]:15332 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760775AbYCFJkj (ORCPT ); Thu, 6 Mar 2008 04:40:39 -0500 Received: by ug-out-1314.google.com with SMTP id z38so3734295ugc.16 for ; Thu, 06 Mar 2008 01:40:38 -0800 (PST) Content-Disposition: inline In-Reply-To: <20080305135448.GA4636@ff.dom.local> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Mar 05, 2008 at 01:54:48PM +0000, Jarek Poplawski wrote: > Hi, > > dev->queue_lock is taken in a scenario like below: always after > dev->ingress_lock and p->tcfc_lock, so just like on this last > backtrace with info about held locks. But this report shows that > lockdep for some reason forgot the history before dev->queue_lock, > and recorded it again. It seems, even if there is something wrong > with init lockdep shouldn't report it like this. ...Hmmm... On the other hand, despite misleading dependency chain on this report, lockdep seems to be right: dev->queue_lock and dev->ingress_lock are really taken in a different order from qdisc_lock_tree() and while using act_mirred! Now I wonder why this warning is so rare? So, let's give a break to lockdep maintainers and linux-kernel, and try to figure it out more in netdev... Jarek P.