[openib-general] SDP can cause IPoIB module to be unable to be removed

[Hal Rosenstock]

Hi Libor,

After using SDP, and unloading SDP, I then attempted to unload IPoIB and
got the following:

unregister_netdevice: waiting for ib0 to become free. Usage count = 1

The simplest way I found to recreate this is:
1. Bring up IPoIB and then SDP
2. Run tcp.aio.x -t <local IPoIB address>
(no server/receiver)
3. Wait for connection refused
4. Unload SDP and then IPoIB

-- Hal