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Message-ID: <CACGeUEgs5+L-9RAvMV45ODQnDVBLBgbfHu+0Ab5Wp1L=iDJQNg@mail.gmail.com>
Date: Sat, 8 Mar 2014 11:41:33 +0100
From: Mirco Tischler <mt-ml@....de>
To: Valdis Kletnieks <valdis.kletnieks@...edu>,
Eric Dumazet <edumazet@...gle.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: next-20131218 - WARNING in qdisc_list_add
> On Thu, 2013-12-19 at 13:14 -0500, Valdis Kletnieks wrote:
> > Seen once while booting next-20131218 (different boot than the BUG
> > I hit). Command that triggered it would have been one of these 2:
> >
> > /usr/sbin/tc qdisc add dev em1 root codel
> > /usr/sbin/tc qdisc add dev wlp3s0 root codel
> >
> > It's possible that wlp3s0 wasn't there yet due to rfkill switch having
> > nuked the wireless.
> >
> > 'git blame' points at the message being added in this commit:
> >
> > commit e57a784d8cae429f5b697fe55abf420181d9ff09
> > Author: Eric Dumazet <edumazet@...gle.com>
> > Date: Thu Dec 12 15:41:56 2013 -0800
> >
> > pkt_sched: set root qdisc before change() in attach_default_qdiscs()
> >
> > After commit 95dc19299f74 ("pkt_sched: give visibility to mq slave
> > qdiscs") we call disc_list_add() while the device qdisc might be
> > the noop_qdisc one.
> >
> > This shows up as duplicates in "tc qdisc show", as all inactive devices
> > point to noop_qdisc.
> >
> > Fix this by setting dev->qdisc to the new qdisc before calling
> > ops->change() in attach_default_qdiscs()
> >
> > Add a WARN_ON_ONCE() to catch any future similar problem.
> >
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Signed-off-by: David S. Miller <davem@...emloft.net>
> >
> >
> > [ 153.876539] ------------[ cut here ]------------
> > [ 153.878667] WARNING: CPU: 1 PID: 1446 at net/sched/sch_api.c:278 qdisc_list_add+0x79/0xcf()
> > [ 153.897042] CPU: 3 PID: 1446 Comm: tc Tainted: G O 3.13.0-rc4-next-20131218 #129
> > [ 153.898877] Hardware name: Dell Inc. Latitude E6530/07Y85M, BIOS A11 03/12/2013
> > [ 153.900666] 0000000000000000 ffff880121195950 ffffffff8164c74f 0000000000000000
> > [ 153.905666] ffff880121195988 ffffffff8103875e ffffffff814afe73 ffff88012828f600
> > [ 153.910847] 0000000000000001 ffffffff81c8cac0 0000000000000001 ffff880121195998
> > [ 153.916012] Call Trace:
> > [ 153.917237] [<ffffffff8164c74f>] dump_stack+0x4f/0xa2
> > [ 153.918659] [<ffffffff8103875e>] warn_slowpath_common+0x7a/0x93
> > [ 153.920222] [<ffffffff814afe73>] ? qdisc_list_add+0x79/0xcf
> > [ 153.921896] [<ffffffff81038816>] warn_slowpath_null+0x15/0x17
> > [ 153.923579] [<ffffffff814afe73>] qdisc_list_add+0x79/0xcf
> > [ 153.925134] [<ffffffff814b1466>] qdisc_create+0x237/0x350
> > [ 153.926658] [<ffffffff814b1a05>] tc_modify_qdisc+0x486/0x4af
> > [ 153.928173] [<ffffffff814a2bb0>] rtnetlink_rcv_msg+0x180/0x193
> > [ 153.929753] [<ffffffff810c7c32>] ? trace_preempt_on+0x12/0x2f
> > [ 153.931453] [<ffffffff814a2a30>] ? rtnl_newlink+0x4ba/0x4ba
> > [ 153.933107] [<ffffffff814b67e4>] netlink_rcv_skb+0x44/0x86
> > [ 153.934586] [<ffffffff8149fbeb>] rtnetlink_rcv+0x1e/0x25
> > [ 153.936133] [<ffffffff814b62ef>] netlink_unicast+0xf1/0x175
> > [ 153.937587] [<ffffffff814b6677>] netlink_sendmsg+0x304/0x34e
> > [ 153.939088] [<ffffffff814794ac>] __sock_sendmsg_nosec+0x25/0x27
> > [ 153.940638] [<ffffffff8147b0c2>] sock_sendmsg+0x52/0x6c
> > [ 153.942278] [<ffffffff811009ce>] ? might_fault+0x9b/0x9f
> > [ 153.943980] [<ffffffff81100985>] ? might_fault+0x52/0x9f
> > [ 153.945439] [<ffffffff81487cec>] ? verify_iovec+0x5e/0xac
> > [ 153.946993] [<ffffffff8147cd41>] ___sys_sendmsg+0x20d/0x29d
> > [ 153.948540] [<ffffffff81073236>] ? arch_local_irq_save+0x9/0xc
> > [ 153.950087] [<ffffffff81072708>] ? up_read+0x22/0x25
> > [ 153.951743] [<ffffffff8165a21b>] ? __do_page_fault+0x56f/0x600
> > [ 153.953495] [<ffffffff810c7bdd>] ? time_hardirqs_on+0x1b/0x2f
> > [ 153.955175] [<ffffffff8113fdee>] ? fcheck_files+0x80/0xe0
> > [ 153.956720] [<ffffffff8114062d>] ? fget_light+0x30/0x90
> > [ 153.958195] [<ffffffff8147d20a>] __sys_sendmsg+0x3d/0x5b
> > [ 153.959645] [<ffffffff8147d235>] SyS_sendmsg+0xd/0x17
> > [ 153.961092] [<ffffffff8165d722>] system_call_fastpath+0x16/0x1b
> > [ 153.965229] ---[ end trace ec29ec2eecd5a461 ]---
> >
>
> Thanks for the report !
>
> Could you try the following patch ?
>
> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> index c31190e29b90..17c03198ebbc 100644
> --- a/net/sched/sch_api.c
> +++ b/net/sched/sch_api.c
> @@ -273,11 +273,12 @@ static struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle)
>
> void qdisc_list_add(struct Qdisc *q)
> {
> - struct Qdisc *root = qdisc_dev(q)->qdisc;
> + if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) {
> + struct Qdisc *root = qdisc_dev(q)->qdisc;
>
> - WARN_ON_ONCE(root == &noop_qdisc);
> - if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS))
> + WARN_ON_ONCE(root == &noop_qdisc);
> list_add_tail(&q->list, &root->list);
> + }
> }
> EXPORT_SYMBOL(qdisc_list_add);
Hi
I can reproduce this warning reliably on 3.14-rc* (by executing tc
qdisc add dev <dev> root fq_codel via udev rule). The abbove patch
fixes it.
Thanks
Mirco
P.S.: I'm not subscribed to the list and couldn't figure out how to
manually set the In-reply-to tag, so sorry for messing up your
threading ;-)
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