Commit eae792b7 authored by David S. Miller's avatar David S. Miller
Browse files

netdev: Add netdev->select_queue() method. 



Devices or device layers can set this to control the queue selection
performed by dev_pick_tx().

This function runs under RCU protection, which allows overriding
functions to have some way of synchronizing with things like dynamic
->real_num_tx_queues adjustments.

This makes the spinlock prefetch in dev_queue_xmit() a little bit
less effective, but that's the price right now for correctness.

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e3c50d5d

include/linux/netdevice.h

+3 −0
Original line number Diff line number Diff line
@@ -724,6 +724,9 @@ struct net_device 
	void                    (*poll_controller)(struct net_device *dev);

#endif



	u16			(*select_queue)(struct net_device *dev,

						struct sk_buff *skb);



#ifdef CONFIG_NET_NS

	/* Network namespace this network device is inside */

	struct net		*nd_net;

net/core/dev.c

+6 −3
Original line number Diff line number Diff line
@@ -1670,6 +1670,9 @@ static struct netdev_queue *dev_pick_tx(struct net_device *dev, 
{

	u16 queue_index = 0;



	if (dev->select_queue)

		queue_index = dev->select_queue(dev, skb);



	skb_set_queue_mapping(skb, queue_index);

	return netdev_get_tx_queue(dev, queue_index);

}
@@ -1710,14 +1713,14 @@ int dev_queue_xmit(struct sk_buff *skb) 
	}



gso:

	txq = dev_pick_tx(dev, skb);

	spin_lock_prefetch(&txq->lock);



	/* Disable soft irqs for various locks below. Also

	 * stops preemption for RCU.

	 */

	rcu_read_lock_bh();



	txq = dev_pick_tx(dev, skb);

	spin_lock_prefetch(&txq->lock);



	/* Updates of qdisc are serialized by queue->lock.

	 * The struct Qdisc which is pointed to by qdisc is now a

	 * rcu structure - it may be accessed without acquiring

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