Subject: Re: [PATCH net v2] vlan: Fix lockdep warning when vlan dev handle notification

From: Ding Tianhong <[email-masked]>
Date: Mon, 17 Mar 2014 11:08:37 +0800

On 2014/3/15 10:02, David Miller wrote:
> From: Ding Tianhong <[email-masked]>
> Date: Thu, 13 Mar 2014 10:22:18 +0800
> 
>> When I open the LOCKDEP config and run these steps:
> 
> This doesn't work?
> 

It make no sense, I have try it before, the class check only focus on the lock_class_key,
not the lockdep_subclass_key.

Regards
Ding

> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
> index 4b65aa4..9ad89ff 100644
> --- a/net/8021q/vlan_dev.c
> +++ b/net/8021q/vlan_dev.c
> @@ -556,10 +556,22 @@ static struct device_type vlan_type = {
>  
>  static const struct net_device_ops vlan_netdev_ops;
>  
> +static int vlan_calculate_locking_subclass(struct net_device *real_dev)
> +{
> +	int subclass = 0;
> +
> +	while (is_vlan_dev(real_dev)) {
> +		subclass++;
> +		real_dev = vlan_dev_priv(real_dev)->real_dev;
> +	}
> +
> +	return subclass;
> +}
> +
>  static int vlan_dev_init(struct net_device *dev)
>  {
>  	struct net_device *real_dev = vlan_dev_priv(dev)->real_dev;
> -	int subclass = 0, i;
> +	int subclass, i;
>  
>  	netif_carrier_off(dev);
>  
> @@ -604,9 +616,7 @@ static int vlan_dev_init(struct net_device *dev)
>  
>  	SET_NETDEV_DEVTYPE(dev, &vlan_type);
>  
> -	if (is_vlan_dev(real_dev))
> -		subclass = 1;
> -
> +	subclass = vlan_calculate_locking_subclass(real_dev);
>  	vlan_dev_set_lockdep_class(dev, subclass);
>  
>  	vlan_dev_priv(dev)->vlan_pcpu_stats = alloc_percpu(struct vlan_pcpu_stats);
> 
> .
>