sunrpc/auth_gss: Call rcu_barrier() on module unload.

As the module uses rcu_call() we should make sure that all
rcu callback has been completed before removing the code.
Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sunrpc/auth_gss/auth_gss.c

@@ -1548,6 +1548,7 @@ static void __exit exit_rpcsec_gss(void)
 {
 	gss_svc_shutdown();
 	rpcauth_unregister(&authgss_ops);
+	rcu_barrier(); /* Wait for completion of call_rcu()'s */
 }
 
 MODULE_LICENSE("GPL");