[v3,2/4] net: Allow for more then a single subclass for netif_addr_lock

Currently netif_addr_lock_nested assumes that there can be only
a single nesting level between 2 devices.  However, if we
have multiple devices of the same type stacked, this fails.
For example:
 eth0 <-- vlan0.10 <-- vlan0.10.20

A more complicated configuration may stack more then one type of
device in different order.
Ex:
  eth0 <-- vlan0.10 <-- macvlan0 <-- vlan1.10.20 <-- macvlan1

This patch adds an ndo_* function that allows each stackable
device to report its nesting level.  If the device doesn't
provide this function default subclass of 1 is used.

Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>
---
 include/linux/netdevice.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

On Fri, 2014-05-16 at 17:04 -0400, Vlad Yasevich wrote:
> Currently netif_addr_lock_nested assumes that there can be only

> a single nesting level between 2 devices.  However, if we

> have multiple devices of the same type stacked, this fails.

> For example:

>  eth0 <-- vlan0.10 <-- vlan0.10.20

> 

> A more complicated configuration may stack more then one type of

> device in different order.

> Ex:

>   eth0 <-- vlan0.10 <-- macvlan0 <-- vlan1.10.20 <-- macvlan1

> 

> This patch adds an ndo_* function that allows each stackable

> device to report its nesting level.  If the device doesn't

> provide this function default subclass of 1 is used.

> 

> Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>

> ---

>  include/linux/netdevice.h | 8 +++++++-

>  1 file changed, 7 insertions(+), 1 deletion(-)

> 

> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h

> index fb912e8..9d4b1f1 100644

> --- a/include/linux/netdevice.h

> +++ b/include/linux/netdevice.h

> @@ -1144,6 +1144,7 @@ struct net_device_ops {

>  	netdev_tx_t		(*ndo_dfwd_start_xmit) (struct sk_buff *skb,

>  							struct net_device *dev,

>  							void *priv);

> +	int			(*ndo_get_lock_subclass)(struct net_device *dev);

>  };

>  

>  /**

> @@ -2950,7 +2951,12 @@ static inline void netif_addr_lock(struct net_device *dev)

>  

>  static inline void netif_addr_lock_nested(struct net_device *dev)

>  {

> -	spin_lock_nested(&dev->addr_list_lock, SINGLE_DEPTH_NESTING);

> +	int subclass = SINGLE_DEPTH_NESTING;

> +

> +	if (dev->netdev_ops->ndo_get_lock_subclass)

> +		subclass = dev->netdev_ops->ndo_get_lock_subclass(dev);

> +

> +	spin_lock_nested(&dev->addr_list_lock, subclass);

>  }

>  


Hi,

I know this has already been applied. However, this commit causes a
warning in include/linux/netdevice.h when W=1

In file included from ixgbe/ixgbe.h:35:0,
                 from ixgbe/ixgbe_lib.c:29:
include/linux/netdevice.h: In function ‘netif_addr_lock_nested’:
include/linux/netdevice.h:2954:6: warning: variable ‘subclass’ set but not used [-Wunused-but-set-variable]
  int subclass = SINGLE_DEPTH_NESTING;
      ^

This only occurs if CONFIG_DEBUG_LOCK_ALLOC=Y, and there seems to be no
easy fix for the warning, due to how spin_lock_nested is a macro that
discards the second parameter when DEBUG_LOCK_ALLOC is disabled.

I'm not sure how big a deal this is, considering that it only occurs at
W=1, and the patch is already committed.

>  static inline void netif_addr_lock_bh(struct net_device *dev)


Regards,
Jake

From: "Keller, Jacob E" <jacob.e.keller@intel.com>
Date: Wed, 4 Jun 2014 21:42:12 +0000

> This only occurs if CONFIG_DEBUG_LOCK_ALLOC=Y, and there seems to be no
> easy fix for the warning, due to how spin_lock_nested is a macro that
> discards the second parameter when DEBUG_LOCK_ALLOC is disabled.

spin_lock_nested(), in that case, should mark the argument as unused.

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On Wed, 2014-06-04 at 14:53 -0700, David Miller wrote:
> From: "Keller, Jacob E" <jacob.e.keller@intel.com>

> Date: Wed, 4 Jun 2014 21:42:12 +0000

> 

> > This only occurs if CONFIG_DEBUG_LOCK_ALLOC=Y, and there seems to be no

> > easy fix for the warning, due to how spin_lock_nested is a macro that

> > discards the second parameter when DEBUG_LOCK_ALLOC is disabled.

> 

> spin_lock_nested(), in that case, should mark the argument as unused.

> 

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Can it do that? spin_lock_nested is a macro.

Thanks,
Jake

On 06/04/2014 05:42 PM, Keller, Jacob E wrote:
> On Fri, 2014-05-16 at 17:04 -0400, Vlad Yasevich wrote:
>> Currently netif_addr_lock_nested assumes that there can be only
>> a single nesting level between 2 devices.  However, if we
>> have multiple devices of the same type stacked, this fails.
>> For example:
>>  eth0 <-- vlan0.10 <-- vlan0.10.20
>>
>> A more complicated configuration may stack more then one type of
>> device in different order.
>> Ex:
>>   eth0 <-- vlan0.10 <-- macvlan0 <-- vlan1.10.20 <-- macvlan1
>>
>> This patch adds an ndo_* function that allows each stackable
>> device to report its nesting level.  If the device doesn't
>> provide this function default subclass of 1 is used.
>>
>> Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>
>> ---
>>  include/linux/netdevice.h | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>> index fb912e8..9d4b1f1 100644
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -1144,6 +1144,7 @@ struct net_device_ops {
>>  	netdev_tx_t		(*ndo_dfwd_start_xmit) (struct sk_buff *skb,
>>  							struct net_device *dev,
>>  							void *priv);
>> +	int			(*ndo_get_lock_subclass)(struct net_device *dev);
>>  };
>>  
>>  /**
>> @@ -2950,7 +2951,12 @@ static inline void netif_addr_lock(struct net_device *dev)
>>  
>>  static inline void netif_addr_lock_nested(struct net_device *dev)
>>  {
>> -	spin_lock_nested(&dev->addr_list_lock, SINGLE_DEPTH_NESTING);
>> +	int subclass = SINGLE_DEPTH_NESTING;
>> +
>> +	if (dev->netdev_ops->ndo_get_lock_subclass)
>> +		subclass = dev->netdev_ops->ndo_get_lock_subclass(dev);
>> +
>> +	spin_lock_nested(&dev->addr_list_lock, subclass);
>>  }
>>  
> 
> Hi,
> 
> I know this has already been applied. However, this commit causes a
> warning in include/linux/netdevice.h when W=1
> 
> In file included from ixgbe/ixgbe.h:35:0,
>                  from ixgbe/ixgbe_lib.c:29:
> include/linux/netdevice.h: In function ‘netif_addr_lock_nested’:
> include/linux/netdevice.h:2954:6: warning: variable ‘subclass’ set but not used [-Wunused-but-set-variable]
>   int subclass = SINGLE_DEPTH_NESTING;
>       ^
> 
> This only occurs if CONFIG_DEBUG_LOCK_ALLOC=Y, and there seems to be no
> easy fix for the warning, due to how spin_lock_nested is a macro that
> discards the second parameter when DEBUG_LOCK_ALLOC is disabled.
> 
> I'm not sure how big a deal this is, considering that it only occurs at
> W=1, and the patch is already committed.
> 

Yuck.  It's actually raw_spin_lock_nested() macro that discards the
subclass argument...

We could do something really silly like:

# define raw_spin_lock_nested(lock, subclass) \
                             sublcass;_raw_spin_lock(lock)

That seems to get rid of the warning for me.

-vlad

>>  static inline void netif_addr_lock_bh(struct net_device *dev)
> 
> Regards,
> Jake
> 
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> 

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