Re: [BUG]: problem when shutting down ppp connection since 2.5.70

[Stephen Hemminger <shemminger@xxxxxxxx>]

The problem is that some protocol is still holding a reference to the device.
This is a bug in the protocol, and needs to be fixed (ie not a ppp bug).

Try building a kernel with only IPv4, eliminate all others then add back until
you find the culprit.

The following patch may help also.

diff -Nru a/net/core/dev.c b/net/core/dev.c
--- a/net/core/dev.c    Wed Jul  9 11:40:56 2003
+++ b/net/core/dev.c    Wed Jul  9 11:40:56 2003
@@ -72,6 +72,8 @@
  *                                     - netif_rx() feedback
  */
 
+#define DEBUG 1
+
 #include <asm/uaccess.h>
 #include <asm/system.h>
 #include <asm/bitops.h>
@@ -2704,6 +2706,8 @@
        goto out;
 }
 
+extern void dst_dumpref(const struct net_device *dev);
+
 static void netdev_wait_allrefs(struct net_device *dev)
 {
        unsigned long rebroadcast_time, warning_time;
@@ -2740,6 +2744,30 @@
                current->state = TASK_RUNNING;
 
                if (time_after(jiffies, warning_time + 10 * HZ)) {
+#ifdef DEBUG
+                       dst_dumpref(dev);
+
+                       if (dev->atalk_ptr)
+                               printk(KERN_INFO "unregister_netdevice: "
+                                      " %s: probably in use as AppleTalk 
device\n", dev->name);
+                       if (dev->ip_ptr)
+                               printk(KERN_INFO "unregister_netdevice: "
+                                      " %s: probably in use as IPv4 device\n", 
dev->name);
+
+                       if (dev->atalk_ptr)
+                               printk(KERN_INFO "unregister_netdevice: "
+                                      " %s: probably in use as DECnet 
device\n", dev->name);
+                       if (dev->ip6_ptr)
+                               printk(KERN_INFO "unregister_netdevice: "
+                                      " %s: probably in use as IPv6 device\n", 
dev->name);
+
+                       if (dev->ec_ptr)
+                               printk(KERN_INFO "unregister_netdevice: "
+                                      " %s: probably in use as Econet 
device\n", dev->name);
+                       if (dev->ax25_ptr)
+                               printk(KERN_INFO "unregister_netdevice: "
+                                      " %s: probably in use as AX.25 
device\n", dev->name);
+#endif
                        printk(KERN_EMERG "unregister_netdevice: "
                               "waiting for %s to become free. Usage "
                               "count = %d\n",
diff -Nru a/net/core/dst.c b/net/core/dst.c
--- a/net/core/dst.c    Wed Jul  9 11:40:56 2003
+++ b/net/core/dst.c    Wed Jul  9 11:40:56 2003
@@ -41,6 +41,21 @@
 static struct timer_list dst_gc_timer =
        TIMER_INITIALIZER(dst_run_gc, 0, DST_GC_MIN);
 
+
+void dst_dumpref(const struct net_device *dev)
+{
+       struct dst_entry *dst;
+       int count = 0;
+
+       spin_lock_bh(&dst_lock);
+       for (dst = dst_garbage_list; dst; dst = dst->next) {
+               if (dst->dev == dev) ++count;
+       }
+       spin_unlock_bh(&dst_lock);
+
+       printk(KERN_INFO "dst route cache has %d references\n", count);
+}
+
 static void dst_run_gc(unsigned long dummy)
 {
        int    delayed = 0;