netpoll: re-enable irq in poll_napi()

napi->poll() needs IRQ enabled, so we have to re-enable IRQ before
calling it.

Cc: David Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/netpoll.c

@@ -168,17 +168,25 @@ static void poll_napi(struct net_device *dev)
 	struct napi_struct *napi;
 	int budget = 16;
 
+	WARN_ON_ONCE(!irqs_disabled());
+
 	list_for_each_entry(napi, &dev->napi_list, dev_list) {
+		local_irq_enable();
 		if (napi->poll_owner != smp_processor_id() &&
 		    spin_trylock(&napi->poll_lock)) {
+			rcu_read_lock_bh();
 			budget = poll_one_napi(rcu_dereference_bh(dev->npinfo),
 					       napi, budget);
+			rcu_read_unlock_bh();
 			spin_unlock(&napi->poll_lock);
 
-			if (!budget)
+			if (!budget) {
+				local_irq_disable();
 				break;
 			}
 		}
+		local_irq_disable();
+	}
 }
 
 static void service_arp_queue(struct netpoll_info *npi)