net: stmmac: fix notifier registration

We cannot register the same netdev notifier multiple times when probing
stmmac devices. Register the notifier only once in module init, and also
make debugfs creation/deletion safe against simultaneous notifier call.

Fixes: 481a7d154cbb ("stmmac: debugfs entry name is not be changed when udev rename device name.")
Signed-off-by: Aaro Koskinen <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

···
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
 
+	rtnl_lock();
+
 	/* Create per netdev entries */
 	priv->dbgfs_dir = debugfs_create_dir(dev->name, stmmac_fs_dir);
 
···
 	debugfs_create_file("dma_cap", 0444, priv->dbgfs_dir, dev,
 			    &stmmac_dma_cap_fops);
 
-	register_netdevice_notifier(&stmmac_notifier);
+	rtnl_unlock();
 }
 
 static void stmmac_exit_fs(struct net_device *dev)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
 
-	unregister_netdevice_notifier(&stmmac_notifier);
 	debugfs_remove_recursive(priv->dbgfs_dir);
 }
 #endif /* CONFIG_DEBUG_FS */
···
 
 	netdev_info(priv->dev, "%s: removing driver", __func__);
 
-#ifdef CONFIG_DEBUG_FS
-	stmmac_exit_fs(ndev);
-#endif
 	stmmac_stop_all_dma(priv);
 
 	stmmac_mac_set(priv, priv->ioaddr, false);
 	netif_carrier_off(ndev);
 	unregister_netdev(ndev);
+#ifdef CONFIG_DEBUG_FS
+	stmmac_exit_fs(ndev);
+#endif
 	phylink_destroy(priv->phylink);
 	if (priv->plat->stmmac_rst)
 		reset_control_assert(priv->plat->stmmac_rst);
···
 	/* Create debugfs main directory if it doesn't exist yet */
 	if (!stmmac_fs_dir)
 		stmmac_fs_dir = debugfs_create_dir(STMMAC_RESOURCE_NAME, NULL);
+	register_netdevice_notifier(&stmmac_notifier);
 #endif
 
 	return 0;
···
 static void __exit stmmac_exit(void)
 {
 #ifdef CONFIG_DEBUG_FS
+	unregister_netdevice_notifier(&stmmac_notifier);
 	debugfs_remove_recursive(stmmac_fs_dir);
 #endif
 }