Re: hotplug mopup

[Andrew Morton <andrewm@uow.edu.au>]

Jeff Garzik wrote:
> 
> Andrew Morton wrote:
> > - On the unregister/removal path, the netdevice layer ensures that
> >   the interface is removed from the kernel namespace prior to launching
> >   `/sbin/hotplug net unregister eth0'.
> >
> >   This means that when handling netdevice unregistration
> >   /sbin/hotplug cannot and must not attempt to do anything with eth0!
> >   Generally it'll fail to find an interface with this name.  If it does
> >   find eth0, it'll be the wrong one due to a race.
> 
> This is not a bug.  'unregister eth0' says to userspace "eth0 just
> disappeared."

Yes.  I was simply pointing out a restriction which is placed upon
/sbin/hotplug in this situation.

> Read my previous messages on the subject:  Add events like NETDEV_UP,
> NETDEV_DOWN, and NETDEV_GOING_DOWN to netdev_event_names[] if you want
> to call /sbin/hotplug for other netdev events.

erm..  I just deleted netdev_event_names[].  Without it, the way to do this
is to put

	net_run_sbin_hotplug(dev, "netdev_going_down");

in the appropriate place.

I deleted it because of the 'Rebroadcast unregister notification' crap
in unregister_netdevice.  If you want the netdev_event_names[] flexibility
back then we probably should kill the rebroadcast stuff.

But now that /sbin/hotplug is run asynchronously (Linus did it!) I
don't think this flexibility buys us much.  You'll end up with
'/sbin/hotplug net netdev_going_down' and '/sbin/hotplug net netdev_down'
running simultaneously.  What can they do?
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