From mboxrd@z Thu Jan 1 00:00:00 1970 From: jamal Subject: Re: circular locking, mirred, 2.6.24.2 Date: Thu, 06 Mar 2008 15:48:42 -0500 Message-ID: <1204836523.4457.103.camel@localhost> References: <20080224222035.M62480@visp.net.lb> <20080225095646.GA4321@ff.dom.local> <20080225104652.M2446@visp.net.lb> <20080225113930.GA4733@ff.dom.local> <20080305103935.M76165@visp.net.lb> <20080306134015.GA4571@ff.dom.local> <1204811995.4440.30.camel@localhost> <20080306175629.GA2876@ami.dom.local> Reply-To: hadi@cyberus.ca Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Denys Fedoryshchenko , netdev@vger.kernel.org To: Jarek Poplawski Return-path: Received: from wx-out-0506.google.com ([66.249.82.231]:59009 "EHLO wx-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759791AbYCFUsr (ORCPT ); Thu, 6 Mar 2008 15:48:47 -0500 Received: by wx-out-0506.google.com with SMTP id h31so77068wxd.4 for ; Thu, 06 Mar 2008 12:48:46 -0800 (PST) In-Reply-To: <20080306175629.GA2876@ami.dom.local> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2008-06-03 at 18:56 +0100, Jarek Poplawski wrote: > Every netdevice after register_netdevice() has its queue_lock and > ingress_lock initialized with the same static lock_class_keys, so unless > changed later, these locks are treated by lockdep as 2 global locks. > So, taking such locks with different order should be reported. ok. > This really > happens in act_mirred, and I don't know yet, why this wasn't reported > earlier. Look closely at those traces again ;-> there are *three* different netdevices involved, one (loopback) seems to be _totaly_ unrelated. Tracing of those locks just seems confused - perhaps the pernet stuff is confusing loopback? > Of course, if there are two different devices this could be safe, but > not always (e.g. thread1 has dev_eth0->ingress_lock and wants > dev_eth1->queue_lock, thread2 has dev_eth1->ingress_lock, wants > dev_eth0->qdisc_lock, and thread3 has dev_eth0->qdisc_lock and wants > dev_eth0->ingress_lock). With ifb this shouldn't be the case, but > anyway we have to tell lockdep that ifb uses a different pair of locks. thread3 can not happen because we dont allow it (the other 2 are not contentious). There are cases where redirecting will cause you problems (example if you redirected to yourself and cause an infinite redirect) which are listed in iproute2/doc. Denys script is fine afaics.