netdev - Re: bond: take rcu lock in bond_poll

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Message-ID: <20180928172556.arqk7ntmnz6lhb6d@codemonkey.org.uk>
Date:   Fri, 28 Sep 2018 13:25:56 -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 09:55:52AM -0700, Cong Wang wrote:
 > On Fri, Sep 28, 2018 at 9:18 AM Dave Jones <davej@...emonkey.org.uk> wrote:
 > >
 > > Callers of bond_for_each_slave_rcu are expected to hold the rcu lock,
 > > otherwise a trace like below is shown
 > 
 > So why not take rcu read lock in netpoll_send_skb_on_dev() where
 > RCU is also assumed?

that does seem to solve the backtrace spew I saw too, so if that's
preferable I can respin the patch.

 > As I said, I can't explain why you didn't trigger the RCU warning in
 > netpoll_send_skb_on_dev()...

netpoll_send_skb_on_dev takes the rcu lock itself.

	Dave