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veth: fix dev refcount race 

When deleting the veth driver, veth_close calls netif_carrier_off
for the two extremities of the network device. netif_carrier_off on
the peer device will fire an event and hold a reference on the peer
device. Just after, the peer is unregistered taking the rtnl_lock while
the linkwatch_event is scheduled. If __linkwatch_run_queue does not
occurs before the unregistering, unregister_netdevice will wait for
the dev refcount to reach zero holding the rtnl_lock and linkwatch_event
will wait for the rtnl_lock and hold the dev refcount.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Lezcano 2008-02-20 00:21:47 -08:00 committed by David S. Miller
parent fa907895b7
commit c15853f2c1
1 changed files with 40 additions and 13 deletions
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53
drivers/net/veth.c
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@ -244,18 +244,6 @@ static int veth_open(struct net_device *dev)
return 0;
}
static int veth_close(struct net_device *dev)
{
struct veth_priv *priv;
if (netif_carrier_ok(dev)) {
priv = netdev_priv(dev);
netif_carrier_off(dev);
netif_carrier_off(priv->peer);
}
return 0;
}
static int veth_dev_init(struct net_device *dev)
{
struct veth_net_stats *stats;
@ -286,13 +274,50 @@ static void veth_setup(struct net_device *dev)
dev->hard_start_xmit = veth_xmit;
dev->get_stats = veth_get_stats;
dev->open = veth_open;
dev->stop = veth_close;
dev->ethtool_ops = &veth_ethtool_ops;
dev->features |= NETIF_F_LLTX;
dev->init = veth_dev_init;
dev->destructor = veth_dev_free;
}
static void veth_change_state(struct net_device *dev)
{
struct net_device *peer;
struct veth_priv *priv;
priv = netdev_priv(dev);
peer = priv->peer;
if (netif_carrier_ok(peer)) {
if (!netif_carrier_ok(dev))
netif_carrier_on(dev);
} else {
if (netif_carrier_ok(dev))
netif_carrier_off(dev);
}
}
static int veth_device_event(struct notifier_block *unused,
unsigned long event, void *ptr)
{
struct net_device *dev = ptr;
if (dev->open != veth_open)
goto out;
switch (event) {
case NETDEV_CHANGE:
veth_change_state(dev);
break;
}
out:
return NOTIFY_DONE;
}
static struct notifier_block veth_notifier_block __read_mostly = {
.notifier_call = veth_device_event,
};
/*
* netlink interface
*/
@ -454,12 +479,14 @@ static struct rtnl_link_ops veth_link_ops = {
static __init int veth_init(void)
{
register_netdevice_notifier(&veth_notifier_block);
return rtnl_link_register(&veth_link_ops);
}
static __exit void veth_exit(void)
{
rtnl_link_unregister(&veth_link_ops);
unregister_netdevice_notifier(&veth_notifier_block);
}
module_init(veth_init);