From: Cong Wang <xiyou.wangcong@gmail.com>
To: Taehee Yoo <ap420073@gmail.com>
Cc: syzbot <syzbot+4ec99438ed7450da6272@syzkaller.appspotmail.com>,
Linux Kernel Network Developers <netdev@vger.kernel.org>
Subject: Re: WARNING: bad unlock balance in sch_direct_xmit
Date: Sat, 11 Jan 2020 15:28:29 -0800 [thread overview]
Message-ID: <CAM_iQpUDd6hFrQwb2TkGpbe5AFOtTMyeVg1-OBfY50vC5CEJnQ@mail.gmail.com> (raw)
In-Reply-To: <CAM_iQpU9EXx7xWAaps2E3DWiZbt25ByCK4sR=njYMHF=KsvLFg@mail.gmail.com>
On Sat, Jan 11, 2020 at 1:53 PM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> The details you provide here are really helpful for me to understand
> the reasons behind your changes. Let me think about this and see how
> I could address both problems. This appears to be harder than I originally
> thought.
Do you think the following patch will make everyone happy?
diff --git a/net/core/dev.c b/net/core/dev.c
index 0ad39c87b7fd..7e885d069707 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9177,22 +9177,10 @@ static void
netdev_unregister_lockdep_key(struct net_device *dev)
void netdev_update_lockdep_key(struct net_device *dev)
{
- struct netdev_queue *queue;
- int i;
-
- lockdep_unregister_key(&dev->qdisc_xmit_lock_key);
lockdep_unregister_key(&dev->addr_list_lock_key);
-
- lockdep_register_key(&dev->qdisc_xmit_lock_key);
lockdep_register_key(&dev->addr_list_lock_key);
lockdep_set_class(&dev->addr_list_lock, &dev->addr_list_lock_key);
- for (i = 0; i < dev->num_tx_queues; i++) {
- queue = netdev_get_tx_queue(dev, i);
-
- lockdep_set_class(&queue->_xmit_lock,
- &dev->qdisc_xmit_lock_key);
- }
}
EXPORT_SYMBOL(netdev_update_lockdep_key);
I think as long as we don't take _xmit_lock nestedly, it is fine. And
most (or all?) of the software netdev's are already lockless, so I can't
think of any case we take more than one _xmit_lock on TX path.
I tested it with the syzbot reproducer and your set master/nomaster
commands, I don't get any lockdep splat.
What do you think?
Thanks!
next prev parent reply other threads:[~2020-01-11 23:29 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-03 15:59 WARNING: bad unlock balance in sch_direct_xmit syzbot
2020-01-05 18:30 ` syzbot
2020-01-05 22:58 ` syzbot
2020-01-07 5:36 ` Cong Wang
2020-01-07 11:30 ` Taehee Yoo
2020-01-08 0:34 ` Cong Wang
2020-01-08 11:42 ` Taehee Yoo
2020-01-09 23:38 ` Cong Wang
2020-01-10 3:06 ` Taehee Yoo
2020-01-10 4:43 ` Cong Wang
2020-01-10 6:02 ` Taehee Yoo
2020-01-11 21:53 ` Cong Wang
2020-01-11 23:28 ` Cong Wang [this message]
2020-01-13 10:53 ` Taehee Yoo
2020-01-14 19:39 ` Cong Wang
2020-01-13 10:13 ` Taehee Yoo
2020-01-13 11:08 ` Dmitry Vyukov
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