Which is the correct way to register a new net_device?

i'm trying to register a new net_device in linux...i can alloc and register it correctly and ifconfig shows it. The problem arrives when i try to put the interface up:

ifconfig my_dev up

A kernel freeze occurs...the problem is present only on x86 machines and i can't figure out the reason...on a pcc machine all works well. The code is very simple:

static struct net_device *my_dev;

static int veth_dev_init(struct net_device *dev);
static int veth_open(struct net_device *dev);
static int veth_close(struct net_device *dev);
static int veth_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd);

static struct veth_priv
{
   ...
};

static struct net_device_ops veth_ops =
{
  .ndo_init = veth_dev_init,
  .ndo_open = veth_open,
  .ndo_stop = veth_close,
  .ndo_do_ioctl = veth_ioctl
};

static int __init veth_init()
{
  my_dev = alloc_netdev(sizeof(struct veth_priv), "my_dev", ether_setup);
  if (my_dev == NULL)
    return -ENOMEM;

  my_dev->netdev_ops = &veth_ops;

  register_netdev(my_dev);
  return 0;
}

static void __exit veth_exit()
{
  unregister_netdev(my_dev);
  free_netdev(my_dev);
}

module_init(veth_init);
module_exit(veth_exit);

The first four functions veth_dev_init, veth_open, veth_close and veth_ioctl simply return 0. Maybe is there a missing field in veth_ops structure?

Thank you all!