On Fri, Sep 28, 2018 at 10:31:39AM -0700, Cong Wang wrote:
> On Fri, Sep 28, 2018 at 10:25 AM Dave Jones <da...@codemonkey.org.uk> wrote:
> >
> > On Fri, Sep 28, 2018 at 09:55:52AM -0700, Cong Wang wrote:
> > > On Fri, Sep 28, 2018 at 9:18 AM Dave Jones <da...@codemonkey.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.
>
>
> >From my observations, netpoll_send_skb_on_dev() does not take
> RCU read lock _and_ it relies on rcu read lock because it calls
> rcu_dereference_bh().
>
> If my observation is correct, you should catch a RCU warning like
> this but within netpoll_send_skb_on_dev().
>
> > > 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.
>
> Could you please point me where exactly is the rcu lock here?
>
> I am too stupid to see it. :)
No, I'm the stupid one. I looked at the tree I had just edited to try your
proposed change.
Now that I've untangled myself, I'll repost with your suggested change.
Dave
