[Bridge] unregister_netdevice: waiting for br0 to become free. Usage count = 1 (2.6.12.3)

[Patrick McHardy]

Stephen Hemminger wrote:
> Two other recent reports are:
> 1. Buggy applications that hold packets in their input queue forever,
>    and/or netfilters.  The socket buffer's contain a reference for
>    packets in flight.

skb->dev doesn't take a reference and is reset before packets are queued
to sockets. dst->dev however does hold a reference and is not reset,
perhaps we should change that.