Need one info in netif_rx_schedule()

["Pranjal Kumar Dutta" <pranjalkumardutta@xxxxxxxxx>]

 

Hi,

           I need one clarification in the following networking  code in Linux 2.6.15.1 . The following function is called from netif_rx to enqueue a new packet (sk_buff) to be processed later by ksoftirq on NET_RX_SOFTIRQ. The *dev argument passed on is softnet_data->backlog_dev

  netif_rx_schedule(&queue->backlog_dev) where queue is of sofnet_data for the CPU.

 

 

static inline void __netif_rx_schedule(struct net_device *dev)
{
 unsigned long flags;

 local_irq_save(flags);
 dev_hold(dev);
 list_add_tail(&dev->poll_list, &__get_cpu_var(softnet_data).poll_list);
 if (dev->quota < 0)
  dev->quota += dev->weight;
 else
  dev->quota = dev->weight;
 __raise_softirq_irqoff(NET_RX_SOFTIRQ);
 local_irq_restore(flags);
}

 

Question:

=======

In the above function I am not able to understand what we are trying to achieve in  the list_add_tail. We are adding the poll_list from the backlog_dev to the poll_list of softnet_data.

Which net_devices the backlog_dev->poll_list contain? And which net_devices the softnet_data->poll_list contain ? If somebody can explain the theory behind this it would be of great help.

 

Thanks,

Pranjal