[PATCH] (3/4) dlci locking and registration changes

[Stephen Hemminger <shemminger@xxxxxxxx>]

Change the locking for the dlci device list and registration.
- use RTNL instead of a private lock (needed for net notifier in next patch).
- reorder the checks in the dlci_add to avoid complicated unwinds
- use dev->destructor to free
- hold RTNL around deassoc to protect callback from races


diff -Nru a/drivers/net/wan/dlci.c b/drivers/net/wan/dlci.c
--- a/drivers/net/wan/dlci.c    Mon Sep  8 14:02:46 2003
+++ b/drivers/net/wan/dlci.c    Mon Sep  8 14:02:46 2003
@@ -58,7 +58,6 @@
 static const char version[] = "DLCI driver v0.35, 4 Jan 1997, 
mike.mclagan@xxxxxxxxx";
 
 static LIST_HEAD(dlci_devs);
-static spinlock_t dlci_dev_lock = SPIN_LOCK_UNLOCKED;
 
 static void dlci_setup(struct net_device *);
 
@@ -360,34 +359,38 @@
        struct net_device       *master, *slave;
        struct dlci_local       *dlp;
        struct frad_local       *flp;
-       int                     err;
+       int                     err = -EINVAL;
 
 
        /* validate slave device */
        slave = dev_get_by_name(dlci->devname);
        if (!slave)
-               return(-ENODEV);
+               return -ENODEV;
 
-       if (slave->type != ARPHRD_FRAD) {
-               dev_put(slave);
-               return(-EINVAL);
-       }
+       if (slave->type != ARPHRD_FRAD || slave->priv == NULL)
+               goto err1;
 
        /* create device name */
        master = alloc_netdev( sizeof(struct dlci_local), "dlci%d",
                              dlci_setup);
        if (!master) {
-               dev_put(slave);
-               return(-ENOMEM);
+               err = -ENOMEM;
+               goto err1;
        }
 
-       err = register_netdev(master);
-       if (err < 0) {
-               dev_put(slave);
-               kfree(master);
-               return(err);
+       /* make sure same slave not already registered */
+       rtnl_lock();
+       list_for_each_entry(dlp, &dlci_devs, list) {
+               if (dlp->slave == slave) {
+                       err = -EBUSY;
+                       goto err2;
+               }
        }
 
+       err = dev_alloc_name(master, master->name);
+       if (err < 0)
+               goto err2;
+
        *(short *)(master->dev_addr) = dlci->dlci;
 
        dlp = (struct dlci_local *) master->priv;
@@ -395,22 +398,27 @@
        dlp->master = master;
 
        flp = slave->priv;
-       err = flp ? (*flp->assoc)(slave, master) : -EINVAL;
+       err = (*flp->assoc)(slave, master);
        if (err < 0)
-       {
-               unregister_netdev(master);
-               dev_put(slave);
-               free_netdev(master);
-               return(err);
-       }
+               goto err2;
+
+       err = register_netdevice(master);
+       if (err < 0) 
+               goto err2;
 
        strcpy(dlci->devname, master->name);
 
-       spin_lock_bh(&dlci_dev_lock);
        list_add(&dlp->list, &dlci_devs);
-       spin_unlock_bh(&dlci_dev_lock);
+       rtnl_unlock();
 
        return(0);
+
+ err2:
+       rtnl_unlock();
+       kfree(master);
+ err1:
+       dev_put(slave);
+       return(err);
 }
 
 static int dlci_del(struct dlci_add *dlci)
@@ -433,21 +441,18 @@
        slave = dlp->slave;
        flp = slave->priv;
 
+       rtnl_lock();
        err = (*flp->deassoc)(slave, master);
-       if (err) 
-               return(err);
-
+       if (!err) {
+               list_del(&dlp->list);
 
-       spin_lock_bh(&dlci_dev_lock);
-       list_del(&dlp->list);
-       spin_unlock_bh(&dlci_dev_lock);
+               unregister_netdevice(master);
 
-       unregister_netdev(master);
-
-       dev_put(slave);
-       free_netdev(master);
+               dev_put(slave);
+       }
+       rtnl_unlock();
 
-       return(0);
+       return(err);
 }
 
 static int dlci_ioctl(unsigned int cmd, void *arg)
@@ -494,6 +499,7 @@
        dev->hard_header        = dlci_header;
        dev->get_stats          = dlci_get_stats;
        dev->change_mtu         = dlci_change_mtu;
+       dev->destructor         = free_netdev;
 
        dlp->receive            = dlci_receive;
 
@@ -518,12 +524,12 @@
        
        dlci_ioctl_set(NULL);
 
+       rtnl_lock();
        list_for_each_entry_safe(dlp, nxt, &dlci_devs, list) {
-               unregister_netdev(dlp->master);
+               unregister_netdevice(dlp->master);
                dev_put(dlp->slave);
-               free_netdev(dlp->master);
        }
-
+       rtnl_unlock();
 }
 
 module_init(init_dlci);