Re: [patch] lockdep annotate vlan net device as being a special class

[Peter Staubach <staubach@redhat.com>]

Arjan van de Ven wrote:

>On Thu, 2006-06-15 at 16:40 +0200, deweerdt@free.fr wrote:
>  
>
>>Hi,
>>
>>Assigning an inet address to a vlanized interface triggered the following BUG
>>from the lock validator (kernel is 2.6.17-rc6-mm2):
>>    
>>
>
>ok below is a real working (cross my fingers) patch against the current
>-mm tree:
>
>vlan network devices have devices nesting below it, and are a special
>"super class" of normal network devices; split their locks off into a
>separate class since they always nest.
>
>Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
>Signed-off-by: Ingo Molnar <mingo@elte.hu>
>---
> net/8021q/vlan.c |   10 ++++++++++
> 1 file changed, 10 insertions(+)
>
>Index: linux-2.6.17-lockdep/net/8021q/vlan.c
>===================================================================
>--- linux-2.6.17-lockdep.orig/net/8021q/vlan.c
>+++ linux-2.6.17-lockdep/net/8021q/vlan.c
>@@ -364,6 +364,14 @@ static void vlan_transfer_operstate(cons
> 	}
> }
> 
>+/*
>+ * vlan network devices have devices nesting below it, and are a special
>+ * "super class" of normal network devices; split their locks off into a
>+ * separate class since they always nest.
>+ */
>+static struct lock_class_key vlan_netdev_xmit_lock_key;
>+
>+
> /*  Attach a VLAN device to a mac address (ie Ethernet Card).
>  *  Returns the device that was created, or NULL if there was
>  *  an error of some kind.
>@@ -460,6 +468,8 @@ static struct net_device *register_vlan_
> 		    
> 	new_dev = alloc_netdev(sizeof(struct vlan_dev_info), name,
> 			       vlan_setup);
>+
>+	lockdep_set_class(&new_dev->_xmit_lock, &vlan_netdev_xmit_lock_key);
> 	if (new_dev == NULL)
> 		goto out_unlock;
>

Shouldn't this test for new_dev being NULL _before_ it gets used?

    Thanx...

       ps