sa_query schedules work on IB asynchronous events.  After
unregistering the async event handler, make sure that this work has
completed before releasing the IB device (and possibly allowing the
sa_query module text to go away).
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
 
        ib_unregister_event_handler(&sa_dev->event_handler);
 
+       flush_scheduled_work();
+
        for (i = 0; i <= sa_dev->end_port - sa_dev->start_port; ++i) {
                ib_unregister_mad_agent(sa_dev->port[i].agent);
                kref_put(&sa_dev->port[i].sm_ah->ref, free_sm_ah);