[BUG] RTNL and flush_scheduled_work deadlocks

[Stephen Hemminger <shemminger@linux-foundation.org>]

Ben found this but the problem seems pretty widespread.

The following places are subject to deadlock between flush_scheduled_work
and the RTNL mutex. What can happen is that a work queue routine (like
bridge port_carrier_check) is waiting forever for RTNL, and the driver
routine has called flush_scheduled_work with RTNL held and is waiting
for the work queue to clear.

Several other places have comments like: "can't call flush_scheduled_work
here or it will deadlock". Most of the problem places are in device close
routine. My recommendation would be to add a check for device netif_running in
what ever work routine is used, and move the flush_scheduled_work to the
remove routine.

8139too.c: rtl8139_close --> rtl8139_stop_thread
r8169.c:   rtl8169_down
cassini.c: cas_change_mtu
iseries_veth.c: veth_stop_connection
s2io.c: s2io_close
sis190.c: sis190_down