System blocks (hangs) on ifconfig up

[<shmulik@xxxxxxxxxxx>]

Hello,

My system is Ubuntu 10.04, running kernel 2.6.32-26-generic.

When ever I try to bring up an ethernet interface up for the second time, my
system becomes unresponsive for 60 seconds - i.e. no mouse, no keyboard, no
screen refresh. etc.

Looking at the driver's code, I could see that it's dev->open() method calls
wait_event_interruptible_timeout() with a timeout of 60 seconds - exactly
the delay I'm seeing.

I have narrowed the code to a bare minimum (see below - loosely based on
dummy.c), which only calls mdelay(10000) in it's dev->open() method, and
still, my system blocks for exactly 10 seconds when I run the following
sequence:

> sudo ifconfig shmulik0 up
> sudo ifconfig shmulik0 down
> sudo ifconfig shmulik0 up

At this point - the system is stuck for 10 seconds.


	Thanks,
	Shmulik.

------------------------------------------------------------------------------

shmulik.c:

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/skbuff.h>

MODULE_AUTHOR("Shmulik Hen");
MODULE_DESCRIPTION("Shmulik's sample network driver");
MODULE_LICENSE("GPL");

static struct net_device *g_dev = NULL;

static int shmulik_set_mac_address(struct net_device *dev, void *p)
{
	struct sockaddr *sa = p;

	if (!is_valid_ether_addr(sa->sa_data))
		return -EADDRNOTAVAIL;

	memcpy(dev->dev_addr, sa->sa_data, ETH_ALEN);
	return 0;
}

static netdev_tx_t shmulik_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	dev_kfree_skb(skb);
	return NETDEV_TX_OK;
}

static int shmulik_open(struct net_device *dev)
{
	mdelay(10000);
	netif_carrier_on(dev);
	netif_start_queue(dev);

	return 0;
}

static int shmulik_close(struct net_device *dev)
{
	netif_stop_queue(dev);
	netif_carrier_off(dev);

	return 0;
}

static const struct net_device_ops shmulik_drv_ops =
{
		.ndo_open		= shmulik_open,
		.ndo_stop		= shmulik_close,
		.ndo_start_xmit		= shmulik_start_xmit,
		.ndo_set_mac_address	= shmulik_set_mac_address,
};

static int __init shmulik_drv_init(void)
{
	int rc;
	struct net_device *dev;

	if (g_dev)
		return -EEXIST;

	dev = alloc_etherdev(0);
	if (!dev)
		return -ENOMEM;

	sprintf(dev->name, "%s%d" , "shmulik", 0);
	dev->tx_queue_len = 0;
	dev->flags |= IFF_NOARP;
	dev->flags &= ~IFF_MULTICAST;
	random_ether_addr(dev->dev_addr);

	dev->netdev_ops = &shmulik_drv_ops;

	rc = register_netdev(dev);
	if (rc)
		goto err_exit;

	g_dev = dev;
	return 0;

err_exit:
	free_netdev(dev);
	return rc;
}

static void __exit shmulik_drv_exit(void)
{
	if (g_dev)
	{
		unregister_netdev(g_dev);
		free_netdev(g_dev);
		g_dev = NULL;
	}
}

module_init(shmulik_drv_init);
module_exit(shmulik_drv_exit);