From: Arvid Brodin <Arvid.Brodin@xdin•com>
To: "netdev@vger•kernel.org" <netdev@vger•kernel.org>
Cc: "David S. Miller" <davem@davemloft•net>,
Stephen Hemminger <shemminger@vyatta•com>,
Bruno Ferreira <balferreira@googlemail•com>,
Arvid Brodin <Arvid.Brodin@xdin•com>,
Christian Borntraeger <borntraeger@de•ibm.com>,
Herbert Xu <herbert@gondor•apana.org.au>
Subject: Re: [RFC] net/hsr: Add support for IEC 62439-3 High-availability Seamless Redundancy
Date: Mon, 14 May 2012 18:11:44 +0000 [thread overview]
Message-ID: <4FB14ADD.3050708@xdin.com> (raw)
In-Reply-To: <4F71BEAD.5080605@enea.com>
On 2012-03-27 15:20, Arvid Brodin wrote:
> Hi!
*snip*
>
> 2) I have a locking problem that I haven't managed to figure out. This happens
> the first time I send any packet (hsr_dev_xmit() in hsr_device.c:121, called
> from hsr_device.c:147). It happens even if I set skb2 to NULL (i.e. only send
> one copy):
>
> =============================================
> [ INFO: possible recursive locking detected ]
> 2.6.37 #118
> ---------------------------------------------
> swapper/0 is trying to acquire lock:
> (_xmit_ETHER#2){+.-...}, at: [<901bf38e>] sch_direct_xmit+0x24/0x152
>
> but task is already holding lock:
> (_xmit_ETHER#2){+.-...}, at: [<901b4d1a>] dev_queue_xmit+0x31e/0x3cc
>
> other info that might help us debug this:
> 4 locks held by swapper/0:
> #0: (&n->timer){+.-...}, at: [<9002bc20>] run_timer_softirq+0x98/0x184
> #1: (rcu_read_lock_bh){.+....}, at: [<901b49fc>] dev_queue_xmit+0x0/0x3cc
> #2: (_xmit_ETHER#2){+.-...}, at: [<901b4d1a>] dev_queue_xmit+0x31e/0x3cc
> #3: (rcu_read_lock_bh){.+....}, at: [<901b49fc>] dev_queue_xmit+0x0/0x3cc
>
> stack backtrace:
> Call trace:
> [<9001c640>] dump_stack+0x18/0x20
> [<90040eac>] validate_chain+0x40c/0x9ac
> [<90041a58>] __lock_acquire+0x60c/0x670
> [<90042f32>] lock_acquire+0x3a/0x48
> [<902201a4>] _raw_spin_lock+0x20/0x44
> [<901bf38e>] sch_direct_xmit+0x24/0x152
> [<901b4c14>] dev_queue_xmit+0x218/0x3cc
> [<9021c2e0>] slave_xmit+0x10/0x14
> [<9021c540>] hsr_dev_xmit+0x88/0x8c
> [<901b4942>] dev_hard_start_xmit+0x3c6/0x480
> [<901b4d34>] dev_queue_xmit+0x338/0x3cc
> [<901e3cd8>] arp_xmit+0x8/0xc
> [<901e4436>] arp_send+0x2a/0x2c
> [<901e4e74>] arp_solicit+0x15c/0x170
> [<901bad0c>] neigh_timer_handler+0x1c0/0x204
> [<9002bc8a>] run_timer_softirq+0x102/0x184
> [<900287d8>] __do_softirq+0x64/0xe0
> [<9002896a>] do_softirq+0x26/0x48
> [<90028a66>] irq_exit+0x2e/0x64
> [<90019f16>] do_IRQ+0x46/0x5c
> [<90018428>] irq_level0+0x18/0x60
> [<9021cc16>] rest_init+0x72/0x98
> [<9000063c>] start_kernel+0x21c/0x258
> [<00000000>] 0x0
>
> Any idea why this happens? I need help!
I've spent a few days digging into this and the key apparently is NETIF_F_LLTX.
The problem seems to be that HARD_TX_LOCK is called more than once, first for my virtual
hsr device and then, recursively, for each of the slaves in turn. (At least that's where
lockdep complains - at __netif_tx_lock(), that is.)
At first I just could not understand why both the VLAN and the bonding code got away with
recursive calls to dev_queue_xmit() but I didn't. After some gooling (a lot, actually) I
found some references to the NETIF_F_LLTX flag (here's one:
http://lwn.net/Articles/121566/). I realised both VLAN and bonding code set this flag. And
sure enough, if I set it for my hsr device lockdep does not complain any more.
But NETIF_F_LLTX is described as deprecated in both netdevice.h and in
Documentation/networking/netdevices.txt. Is there an alternative solution that I should
use instead?
(To recap, a hsr device is a virtual device which uses two Ethernet devices as slaves.
This gives redundancy with instant failover, and since nodes are connected in a ring
topology, uses less cabling than duplication.)
--
Arvid Brodin | Consultant (Linux)
XDIN AB | Jan Stenbecks Torg 17 | SE-164 40 Kista | Sweden | xdin.com
next prev parent reply other threads:[~2012-05-14 18:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-27 13:20 [RFC] net/hsr: Add support for IEC 62439-3 High-availability Seamless Redundancy Arvid Brodin
2012-04-03 18:37 ` Stephen Hemminger
2012-04-04 23:09 ` Arvid Brodin
2012-04-04 23:55 ` Stephen Hemminger
2012-04-05 0:21 ` David Miller
2012-04-06 15:51 ` Arvid Brodin
2012-04-06 16:43 ` David Miller
2012-04-06 17:08 ` Arvid Brodin
2012-04-06 17:06 ` Ben Hutchings
2012-04-06 18:19 ` Stephen Hemminger
2012-04-11 0:00 ` Arvid Brodin
2012-04-11 1:28 ` Stephen Hemminger
2012-04-11 14:39 ` Arvid Brodin
2012-04-05 0:17 ` David Miller
2012-04-05 19:21 ` Ben Hutchings
2012-04-05 22:31 ` David Miller
2012-05-14 18:11 ` Arvid Brodin [this message]
2012-05-14 18:28 ` Stephen Hemminger
2012-05-24 17:09 ` Arvid Brodin
2012-05-24 17:16 ` Stephen Hemminger
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4FB14ADD.3050708@xdin.com \
--to=arvid.brodin@xdin$(echo .)com \
--cc=balferreira@googlemail$(echo .)com \
--cc=borntraeger@de$(echo .)ibm.com \
--cc=davem@davemloft$(echo .)net \
--cc=herbert@gondor$(echo .)apana.org.au \
--cc=netdev@vger$(echo .)kernel.org \
--cc=shemminger@vyatta$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox