Re: [Linux-ATM-General] zeppelin causes kernel oops in 2.6.31 with linux-atm-2.5.1 with LEC interfaces.

[Chas W. (CONTRACTOR) <ch...@cm...>]

In message <OF2...@gd...>,Jayson A Dyke writes:
>I'm using the linux kernel v2.6.31 and using linux-atm to create a LEC 
>interface. Every time I go to start zeppelin it causes a kernel oops. The 
>text of that kernel oops is BUG: unable to handle kernel NULL pointer 
>dereferenced at (null). After some investigation by git bisecting the 
>kernel, I narrowed it down to one commit (SHA1: e3804cbebb67887) that 
>removed a deprecated kernel configuration option of COMPAT_NET_DEV_OPS.
>
>I tried this with linux-atm 2.4.1, 2.5.1 and pulling the current 
>development source and compiling it.
>
>Does anyone have any ideas on how to fix this? I need that interface for 
>something and its only a LEC.

there have been two problems recently in the kernel with the lec driver.
i have attached there here in hopes of solving your problem.  it would
be a bit more helpful to get a traceback though from your oops.  the
first one is likely your problem, lec_init() was happening too late.

commit eb0445887a45a3705522aac6c2d8367e90358792
Author: chas williams - CONTRACTOR <ch...@cm...>
Date:   Fri Dec 4 05:19:30 2009 +0000

    atm: [lec] initialize .netdev_ops before calling register_netdev()
    
    fix oops when initializing lane interfaces. lec should probably be
    changed to use alloc_netdev() instead.
    
    Signed-off-by: Chas Williams - CONTRACTOR <ch...@cm...>
    Signed-off-by: David S. Miller <da...@da...>

diff --git a/net/atm/lec.c b/net/atm/lec.c
index b2d6445..42749b7 100644
--- a/net/atm/lec.c
+++ b/net/atm/lec.c
@@ -62,7 +62,6 @@ static int lec_open(struct net_device *dev);
 static netdev_tx_t lec_start_xmit(struct sk_buff *skb,
 				  struct net_device *dev);
 static int lec_close(struct net_device *dev);
-static void lec_init(struct net_device *dev);
 static struct lec_arp_table *lec_arp_find(struct lec_priv *priv,
 					  const unsigned char *mac_addr);
 static int lec_arp_remove(struct lec_priv *priv,
@@ -670,13 +669,6 @@ static const struct net_device_ops lec_netdev_ops = {
 	.ndo_set_multicast_list	= lec_set_multicast_list,
 };
 
-
-static void lec_init(struct net_device *dev)
-{
-	dev->netdev_ops = &lec_netdev_ops;
-	printk("%s: Initialized!\n", dev->name);
-}
-
 static const unsigned char lec_ctrl_magic[] = {
 	0xff,
 	0x00,
@@ -893,6 +885,7 @@ static int lecd_attach(struct atm_vcc *vcc, int arg)
 			dev_lec[i] = alloc_etherdev(size);
 		if (!dev_lec[i])
 			return -ENOMEM;
+		dev_lec[i]->netdev_ops = &lec_netdev_ops;
 		snprintf(dev_lec[i]->name, IFNAMSIZ, "lec%d", i);
 		if (register_netdev(dev_lec[i])) {
 			free_netdev(dev_lec[i]);
@@ -901,7 +894,6 @@ static int lecd_attach(struct atm_vcc *vcc, int arg)
 
 		priv = netdev_priv(dev_lec[i]);
 		priv->is_trdev = is_trdev;
-		lec_init(dev_lec[i]);
 	} else {
 		priv = netdev_priv(dev_lec[i]);
 		if (priv->lecd)


commit cf932353403c7e477a6c6596c0a6a23c6db5f406
Author: root <ro...@re...>
Date:   Fri Jul 16 19:33:19 2010 -0400

    atm: [lec] hold the rtnl lock around dev_set_mtu()
    
    Signed-off-by: Chas Williams - CONTRACTOR <ch...@cm...>

diff --git a/net/atm/lec.c b/net/atm/lec.c
index d98bde1..d6b5511 100644
--- a/net/atm/lec.c
+++ b/net/atm/lec.c
@@ -491,9 +491,11 @@ static int lec_atm_send(struct atm_vcc *vcc, struct sk_buff *skb)
 		priv->lane2_ops = NULL;
 		if (priv->lane_version > 1)
 			priv->lane2_ops = &lane2_ops;
+		rtnl_lock();
 		if (dev_set_mtu(dev, mesg->content.config.mtu))
 			pr_info("%s: change_mtu to %d failed\n",
 				dev->name, mesg->content.config.mtu);
+		rtnl_unlock();
 		priv->is_proxy = mesg->content.config.is_proxy;
 		break;
 	case l_flush_tran_id: