net: transition netdev reg state earlier in run_todo

In prep for unregistering netdevs out of order move the netdev
state validation and change outside of the loop.

While at it modernize this code and use WARN() instead of
pr_err() + dump_stack().
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/20220215225310.3679266-1-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/dev.c

@@ -9906,6 +9906,7 @@ static void netdev_wait_allrefs(struct net_device *dev)
  */
 void netdev_run_todo(void)
 {
+	struct net_device *dev, *tmp;
 	struct list_head list;
 #ifdef CONFIG_LOCKDEP
 	struct list_head unlink_list;
@@ -9926,24 +9927,23 @@ void netdev_run_todo(void)
 
 	__rtnl_unlock();
 
-
 	/* Wait for rcu callbacks to finish before next phase */
 	if (!list_empty(&list))
 		rcu_barrier();
 
-	while (!list_empty(&list)) {
-		struct net_device *dev
-			= list_first_entry(&list, struct net_device, todo_list);
-		list_del(&dev->todo_list);
-
+	list_for_each_entry_safe(dev, tmp, &list, todo_list) {
 		if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
-			pr_err("network todo '%s' but state %d\n",
-			       dev->name, dev->reg_state);
-			dump_stack();
+			netdev_WARN(dev, "run_todo but not unregistering\n");
+			list_del(&dev->todo_list);
 			continue;
 		}
 
 		dev->reg_state = NETREG_UNREGISTERED;
+	}
+
+	while (!list_empty(&list)) {
+		dev = list_first_entry(&list, struct net_device, todo_list);
+		list_del(&dev->todo_list);
 
 		netdev_wait_allrefs(dev);