With new transparent VF support, it is possible to get a deadlock
when some of the deferred work is running and the unregister_vf
is trying to cancel the work element. The solution is to use
trylock and reschedule (similar to bonding and team device).
Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com> Fixes: 0c195567a8f6 ("netvsc: transparent VF management") Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com> Signed-off-by: David S. Miller <davem@davemloft.net>