net: make sure napi_list is safe for RCU traversal

netpoll needs to traverse dev->napi_list under RCU, make
sure it uses the right iterator and that removal from this
list is handled safely.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -6656,7 +6656,7 @@ void __netif_napi_del(struct napi_struct *napi)
 		return;
 
 	napi_hash_del(napi);
-	list_del_init(&napi->dev_list);
+	list_del_rcu(&napi->dev_list);
 	napi_free_frags(napi);
 
 	flush_gro_hash(napi);

net/core/netpoll.c

@@ -297,7 +297,7 @@ static int netpoll_owner_active(struct net_device *dev)
 {
 	struct napi_struct *napi;
 
-	list_for_each_entry(napi, &dev->napi_list, dev_list) {
+	list_for_each_entry_rcu(napi, &dev->napi_list, dev_list) {
 		if (napi->poll_owner == smp_processor_id())
 			return 1;
 	}