netdev - Re: bond: take rcu lock in bond_poll

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Date:   Fri, 28 Sep 2018 15:49:24 -0400
From:   Dave Jones <davej@...emonkey.org.uk>
To:     Cong Wang <xiyou.wangcong@...il.com>
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 12:03:22PM -0700, Cong Wang wrote:
 > 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...

I was wondering for a moment why I never got a warning, then I
remembered I disabled lockdep for that machine because nfs spews stuff.

I'll doublecheck, and post v4. lol, this looked like a 2 minute fix at first.

	Dave