From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: Re: [PATCH][PPPOL2TP]: Fix SMP oops in pppol2tp driver Date: Tue, 19 Feb 2008 10:30:47 +0000 Message-ID: <20080219103047.GA3898@ff.dom.local> References: <47B17BCD.2070903@katalix.com> <20080214130016.GA2583@ff.dom.local> <47BA0214.40703@katalix.com> <20080218.202934.79548477.davem@davemloft.net> <47BA9B50.8040404@katalix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , netdev@vger.kernel.org To: James Chapman Return-path: Received: from mu-out-0910.google.com ([209.85.134.187]:23150 "EHLO mu-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753687AbYBSK35 (ORCPT ); Tue, 19 Feb 2008 05:29:57 -0500 Received: by mu-out-0910.google.com with SMTP id i10so2068104mue.5 for ; Tue, 19 Feb 2008 02:29:55 -0800 (PST) Content-Disposition: inline In-Reply-To: <47BA9B50.8040404@katalix.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Feb 19, 2008 at 09:03:12AM +0000, James Chapman wrote: > David Miller wrote: >> From: James Chapman >> Date: Mon, 18 Feb 2008 22:09:24 +0000 >> >>> Here's a new version of the patch. The patch avoids disabling irqs >>> and fixes the sk_dst_get() usage that DaveM mentioned. But even with >>> this patch, lockdep still complains if hundreds of ppp sessions are >>> inserted into a tunnel as rapidly as possible (lockdep trace is >>> below). I can stop these errors by wrapping the call to ppp_input() >>> in pppol2tp_recv_dequeue_skb() with local_irq_save/restore. What is >>> a better fix? >> >> Firstly, let's fix one thing at a time. Leave the sk_dst_get() >> thing alone until we can prove that it's part of the lockdep >> traces. > > In reproducing the problem, I obtained several lockdep traces that > implicated sk_dst_get(). As a matter of fact I missed just that kind information on previous lockdep report, so if you could send them too this should be still helpful. ... > I agree. I'm seeking advice on what the underlying cause is of this new > trace. IMHO, just like I wrote earlier, the main problem is in ppp_generic(), especially ppp_connect_channel(), where main tx & rx locks are used. I didn't know enough about this sk_dst_lock traces yet. I hope I could help with this, but after these changes I need some time to figure this out again. Jarek P.