Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755459AbbKDE6o (ORCPT ); Tue, 3 Nov 2015 23:58:44 -0500 Received: from mail-pa0-f54.google.com ([209.85.220.54]:36228 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755057AbbKDE6m (ORCPT ); Tue, 3 Nov 2015 23:58:42 -0500 Message-ID: <1446613120.4184.9.camel@edumazet-glaptop2.roam.corp.google.com> Subject: Re: kernel panic in 4.2.3, rb_erase in sch_fq From: Eric Dumazet To: Denys Fedoryshchenko Cc: Cong Wang , Jamal Hadi Salim , "David S. Miller" , netdev , linux-kernel@vger.kernel.org Date: Tue, 03 Nov 2015 20:58:40 -0800 In-Reply-To: <1446612381.4184.7.camel@edumazet-glaptop2.roam.corp.google.com> References: <0705e2b76150c28341d7e1915433450d@visp.net.lb> <1446612381.4184.7.camel@edumazet-glaptop2.roam.corp.google.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2324 Lines: 66 On Tue, 2015-11-03 at 20:46 -0800, Eric Dumazet wrote: > On Wed, 2015-11-04 at 06:25 +0200, Denys Fedoryshchenko wrote: > > On 2015-11-04 00:06, Cong Wang wrote: > > > On Mon, Nov 2, 2015 at 6:11 AM, Denys Fedoryshchenko > > > wrote: > > >> Hi! > > >> > > >> Actually seems i was getting this panic for a while (once per week) on > > >> loaded pppoe server, but just now was able to get full panic message. > > >> After checking commit logs on sch_fq.c i didnt seen any fixes, so > > >> probably > > >> upgrading to newer kernel wont help? > > > > > > > > > Can you share your `tc qdisc show dev xxxx` with us? And how to > > > reproduce > > > it? I tried to setup htb+fq and then flip the interface back and forth > > > but I don't > > > see any crash. > > My guess it wont be easy to reproduce, it is happening on box with 4.5k > > interfaces, that constantly create/delete interfaces, > > and even with that this problem may happen once per day, or may not > > happen for 1 week. > > > > Here is script that is being fired after new ppp interface detected. But > > pppoe process are independent from > > process that are "establishing" shapers. > > > It is probably a generic bug. sch_fq seems OK to me. > > Somehow nobody tries to change qdisc hundred times per second ;) > > Could you try following patch ? > > It seems to 'fix' the issue for me. Following patch would be more appropriate. Prior one was meant to 'show' the issue. diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index cb5d4ad32946..7f5f3e8a10f5 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -706,9 +706,11 @@ struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue, spin_lock_bh(root_lock); /* Prune old scheduler */ - if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1) - qdisc_reset(oqdisc); - + if (oqdisc) { + if (atomic_read(&oqdisc->refcnt) <= 1) + qdisc_reset(oqdisc); + set_bit(__QDISC_STATE_DEACTIVATED, &oqdisc->state); + } /* ... and graft new one */ if (qdisc == NULL) qdisc = &noop_qdisc; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/