hv_netvsc: use RCU to protect vf_netdev

The vf_netdev pointer in the netvsc device context can simply be protected
by RCU because network device destruction is already RCU synchronized.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index 284b97b..6b79487 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -695,7 +695,7 @@
 	bool start_remove;
 
 	/* State to manage the associated VF interface. */
-	struct net_device *vf_netdev;
+	struct net_device __rcu *vf_netdev;
 	bool vf_inject;
 	atomic_t vf_use_cnt;
 	/* 1: allocated, serial number is valid. 0: not allocated */