netdev - Re: bond: take rcu lock in bond_poll

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Message-ID: <CAM_iQpUdoyhKKYOgYtMBv__ZX81R9N2Ox-mftP5mTbgb1h=kfg@mail.gmail.com>
Date:   Fri, 28 Sep 2018 12:03:22 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Dave Jones <davej@...emonkey.org.uk>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: bond: take rcu lock in bond_poll_controller

On Fri, Sep 28, 2018 at 12:02 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> On Fri, Sep 28, 2018 at 11:26 AM Dave Jones <davej@...emonkey.org.uk> wrote:
> > diff --git a/net/core/netpoll.c b/net/core/netpoll.c
> > index 3219a2932463..4f9494381635 100644
> > --- a/net/core/netpoll.c
> > +++ b/net/core/netpoll.c
> > @@ -330,6 +330,7 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
> >         /* It is up to the caller to keep npinfo alive. */
> >         struct netpoll_info *npinfo;
> >
> > +       rcu_read_lock();
> >         lockdep_assert_irqs_disabled();
> >
> >         npinfo = rcu_dereference_bh(np->dev->npinfo);
>
> I think you probably need rcu_read_lock_bh() to satisfy
> rcu_deference_bh()...

But irq is disabled here, so not sure if rcu_read_lock_bh()
could cause trouble... Interesting...