netdev - Re: [Patch net-next 1/2] net: partially revert dynamic lockdep key changes

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Date:   Sat, 2 May 2020 21:24:00 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Taehee Yoo <ap420073@...il.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        syzbot <syzbot+aaa6fa4949cc5d9b7b25@...kaller.appspotmail.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [Patch net-next 1/2] net: partially revert dynamic lockdep key changes

On Sat, May 2, 2020 at 12:36 AM Taehee Yoo <ap420073@...il.com> wrote:
>
> On Fri, 1 May 2020 at 15:02, Cong Wang <xiyou.wangcong@...il.com> wrote:
> >
>
> Hi Cong,
>
> > On Thu, Apr 30, 2020 at 12:40 AM Taehee Yoo <ap420073@...il.com> wrote:
> > > > +static void vlan_dev_set_lockdep_one(struct net_device *dev,
> > > > +                                    struct netdev_queue *txq,
> > > > +                                    void *_subclass)
> > > > +{
> > > > +       lockdep_set_class_and_subclass(&txq->_xmit_lock,
> > > > +                                      &vlan_netdev_xmit_lock_key,
> > > > +                                      *(int *)_subclass);
> > >
> > > I think lockdep_set_class() is enough.
> > > How do you think about it?
> >
> > Good catch. I overlooked this one. Is lockdep_set_class() safe
> > for vlan stacked on vlan?
> >
>
> I think this is safe because of the LLTX flag.
> Also, I tested nested VLAN interfaces with lockdep_set_class().
> I didn't see any lockdep warning.

Great! I will update and send v2.

Thanks.