Subject: [PATCH] atm: clip causes unregister hang

From: Stephen Hemminger <[email-masked]>
Date: Wed, 12 Apr 2006 12:45:33 -0700

If Classical IP over ATM module is loaded, its neighbor table gets
populated when permanent neighbor entries are created; but these entries
are not flushed when the device is removed. Since the entry never gets
flushed the unregister of the network device never completes.

Bug-reference: http://bugzilla.kernel.org/show_bug.cgi?id=6295
Signed-off-by: Stephen Hemminger <[email-masked]>

--- linux-2.6.16.2.orig/net/atm/clip.c	2006-04-12 10:10:43.000000000 -0700
+++ linux-2.6.16.2/net/atm/clip.c	2006-04-12 11:22:47.000000000 -0700
@@ -613,12 +613,19 @@

 static int clip_device_event(struct notifier_block *this,unsigned long event,
-    void *dev)
+			     void *arg)
 {
+	struct net_device *dev = arg;
+
+	if (event == NETDEV_UNREGISTER) {
+		neigh_ifdown(&clip_tbl, dev);
+		return NOTIFY_DONE;
+	}
+
 	/* ignore non-CLIP devices */
-	if (((struct net_device *) dev)->type != ARPHRD_ATM ||
-	    ((struct net_device *) dev)->hard_start_xmit != clip_start_xmit)
+	if (dev->type != ARPHRD_ATM || dev->hard_start_xmit != clip_start_xmit)
 		return NOTIFY_DONE;
+
 	switch (event) {
 		case NETDEV_UP:
 			DPRINTK("clip_device_event NETDEV_UP\n");
@@ -688,8 +695,7 @@
 	DPRINTK("atmarpd_close\n");
 	atmarpd = NULL; /* assumed to be atomic */
 	barrier();
-	unregister_inetaddr_notifier(&clip_inet_notifier);
-	unregister_netdevice_notifier(&clip_dev_notifier);
+
 	if (skb_peek(&sk_atm(vcc)->sk_receive_queue))
 		printk(KERN_ERR "atmarpd_close: closing with requests "
 		    "pending\n");
@@ -731,10 +737,6 @@
 	vcc->push = NULL;
 	vcc->pop = NULL; /* crash */
 	vcc->push_oam = NULL; /* crash */
-	if (register_netdevice_notifier(&clip_dev_notifier))
-		printk(KERN_ERR "register_netdevice_notifier failed\n");
-	if (register_inetaddr_notifier(&clip_inet_notifier))
-		printk(KERN_ERR "register_inetaddr_notifier failed\n");
 	return 0;
 }
 
@@ -992,6 +994,8 @@
 
 	clip_tbl_hook = &clip_tbl;
 	register_atm_ioctl(&clip_ioctl_ops);
+	register_netdevice_notifier(&clip_dev_notifier);
+	register_inetaddr_notifier(&clip_inet_notifier);
 
 #ifdef CONFIG_PROC_FS
 {
@@ -1012,6 +1016,9 @@
 
 	remove_proc_entry("arp", atm_proc_root);
 
+	unregister_inetaddr_notifier(&clip_inet_notifier);
+	unregister_netdevice_notifier(&clip_dev_notifier);
+
 	deregister_atm_ioctl(&clip_ioctl_ops);
 
 	/* First, stop the idle timer, so it stops banging