Re: [PATCH 2.5.67] Update VLAN to new module semantics

From: Stephen Hemminger (shemminger@osdl.org)
Date: Tue Apr 08 2003 - 18:03:23 EST


On Tue, 08 Apr 2003 15:25:27 -0700 (PDT)
"David S. Miller" <davem@redhat.com> wrote:

> From: Stephen Hemminger <shemminger@osdl.org>
> Date: Tue, 8 Apr 2003 11:28:05 -0700
>
> /* NOTE: We have a reference to the real device,
> * so hold on to the reference.
> */
> - MOD_INC_USE_COUNT; /* Add was a success!! */
> + try_module_get(THIS_MODULE);
> +
>
> You have to check the return value and error accordingly.
> The administrator can do a waiting module unload which causes
> all try_module_get()'s to fail so that no new references can
> be added to the module.
>
> Please, if you're going to convert things, do it correctly.

That's what I get for copying bugs from other code ...

Here is a repost which handles the race of unload and uncompleted init.

diff -urN -X dontdiff linux-2.5/net/8021q/vlan.c linux-2.5-vlan/net/8021q/vlan.c
--- linux-2.5/net/8021q/vlan.c 2003-04-03 12:13:09.000000000 -0800
+++ linux-2.5-vlan/net/8021q/vlan.c 2003-04-08 15:49:45.000000000 -0700
@@ -29,7 +29,6 @@
 #include <net/p8022.h>
 #include <net/arp.h>
 #include <linux/rtnetlink.h>
-#include <linux/brlock.h>
 #include <linux/notifier.h>
 
 #include <linux/if_vlan.h>
@@ -68,7 +67,6 @@
         .dev =NULL,
         .func = vlan_skb_recv, /* VLAN receive method */
         .data = (void *)(-1), /* Set here '(void *)1' when this code can SHARE SKBs */
- .next = NULL
 };
 
 /* End of global variables definitions. */
@@ -231,9 +229,8 @@
                                 real_dev->vlan_rx_kill_vid(real_dev, vlan_id);
                         }
 
- br_write_lock(BR_NETPROTO_LOCK);
                         grp->vlan_devices[vlan_id] = NULL;
- br_write_unlock(BR_NETPROTO_LOCK);
+ synchronize_net();
 
 
                         /* Caller unregisters (and if necessary, puts)
@@ -266,7 +263,7 @@
                                 ret = 1;
                         }
 
- MOD_DEC_USE_COUNT;
+ module_put(THIS_MODULE);
                 }
         }
 
@@ -433,6 +430,7 @@
         /* set up method calls */
         new_dev->init = vlan_dev_init;
         new_dev->destructor = vlan_dev_destruct;
+ new_dev->owner = THIS_MODULE;
             
         /* new_dev->ifindex = 0; it will be set when added to
          * the global list.
@@ -540,16 +538,22 @@
         register_netdevice(new_dev);
 
         rtnl_unlock();
-
+
         /* NOTE: We have a reference to the real device,
          * so hold on to the reference.
          */
- MOD_INC_USE_COUNT; /* Add was a success!! */
+ if (!try_module_get(THIS_MODULE))
+ goto out_module_dying;
+
 #ifdef VLAN_DEBUG
         printk(VLAN_DBG "Allocated new device successfully, returning.\n");
 #endif
         return new_dev;
 
+out_module_dying:
+ rtnl_lock();
+ unregister_netdevice(new_dev);
+
 out_free_newdev_priv:
         kfree(new_dev->priv);
 
diff -urN -X dontdiff linux-2.5/net/8021q/vlan_dev.c linux-2.5-vlan/net/8021q/vlan_dev.c
--- linux-2.5/net/8021q/vlan_dev.c 2003-04-03 12:13:09.000000000 -0800
+++ linux-2.5-vlan/net/8021q/vlan_dev.c 2003-04-08 15:50:58.000000000 -0700
@@ -31,7 +31,6 @@
 #include <net/datalink.h>
 #include <net/p8022.h>
 #include <net/arp.h>
-#include <linux/brlock.h>
 
 #include "vlan.h"
 #include "vlanproc.h"
-
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