Roland Dreier wrote:
> > The action in bonding to a detach of slave is to unregister the master
> (see patch 10).
> > This can't be done from the context of unregister_netdevice itself (it is
> protected by rtnl_lock).
>
> I'm confused. Your patch has:
>
> > + ipoib_slave_detach(cpriv->dev);
> > unregister_netdev(cpriv->dev);
>
> And ipoib_slave_detach() is:
>
> > +static inline void ipoib_slave_detach(struct net_device *dev)
> > +{
> > + rtnl_lock();
> > + netdev_slave_detach(dev);
> > + rtnl_unlock();
> > +}
>
> so you are calling netdev_slave_detach() with the rtnl lock held.
> Why can't you make the same call from the start of unregister_netdevice()?
>
> Anyway, if the rtnl lock is a problem, can you just add the call to
> netdev_slave_detach() to unregister_netdev() before it takes the rtnl lock?
>
> - R.
>
Your comment made me do a little rethinking.
In bonding, device is released by calling unregister_netdevice() that doesn't
take the rtnl_lock (unlike unregister_netdev() that does). I guess that this
made me
confused to think that this is not possible. So, I guess I could put
the detach notification in unregister_netedev() and the reaction to the
notification
in the bonding driver would not block.
However, I looked one more time at the code of unregister_netdevice() and found
out that
nothing prevents from calling unregister_netdevice() again when the
notification NETDEV_GOING_DOWN
is sent. I tried that and it works.
I have a new set of patches without sending a slave detach and I will send it
soon.
Thanks for the comment Roland. It makes this patch simpler.
I'd also like to give a credit to Jay for the idea of using NETDEV_GOING_DOWN
notification
instead of NETDEV_CHANGE+IFF_SLAVE_DETACH. He suggested it a while ago but I
wrongly thought that
it wouldn't work.
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