http://lxr.free-electrons.com/source/net/core/dev.c#L26882688 static void net_rx_action(struct softirq_action *h) 2689 { 2690 struct list_head *list = &__get_cpu_var(softnet_data).poll_list; 2691 unsigned long time_limit = jiffies + 2; 2692 int budget = netdev_budget; 2693 void *have; 2694 2695 local_irq_disable(); 2696 2697 while (!list_empty(list)) { 2698 struct napi_struct *n; 2699 int work, weight; 2700 2701 /* If softirq window is exhuasted then punt. 2702 * Allow this to run for 2 jiffies since which will allow 2703 * an average latency of 1.5/HZ. 2704 */ 2705 if (unlikely(budget <= 0 || time_after(jiffies, time_limit))) 2706 goto softnet_break; 2707 2708 local_irq_enable(); 2709 2710 /* Even though interrupts have been re-enabled, this 2711 * access is safe because interrupts can only add new 2712 * entries to the tail of this list, and only ->poll() 2713 * calls can remove this head entry from the list. 2714 */ 2715 n = list_entry(list->next, struct napi_struct, poll_list); 2716 2717 have = netpoll_poll_lock(n); 2718 2719 weight = n->weight; 2720 2721 /* This NAPI_STATE_SCHED test is for avoiding a race 2722 * with netpoll's poll_napi(). Only the entity which 2723 * obtains the lock and sees NAPI_STATE_SCHED set will 2724 * actually make the ->poll() call. Therefore we avoid 2725 * accidently calling ->poll() when NAPI is not scheduled. 2726 */ 2727 work = 0; 2728 if (test_bit(NAPI_STATE_SCHED, &n->state)) 2729 work = n->poll(n, weight); 2730 2731 WARN_ON_ONCE(work > weight); 2732 2733 budget -= work; 2734 2735 local_irq_disable(); 2736 2737 /* Drivers must not modify the NAPI state if they 2738 * consume the entire weight. In such cases this code 2739 * still "owns" the NAPI instance and therefore can 2740 * move the instance around on the list at-will. 2741 */ 2742 if (unlikely(work == weight)) { 2743 if (unlikely(napi_disable_pending(n))) 2744 __napi_complete(n); 2745 else 2746 list_move_tail(&n->poll_list, list); 2747 } 2748 2749 netpoll_poll_unlock(have); 2750 } 2751 out: 2752 local_irq_enable(); 2753 2754 #ifdef CONFIG_NET_DMA 2755 /* 2756 * There may not be any more sk_buffs coming right now, so push 2757 * any pending DMA copies to hardware 2758 */ 2759 dma_issue_pending_all(); 2760 #endif 2761 2762 return; 2763 2764 softnet_break: 2765 __get_cpu_var(netdev_rx_stat).time_squeeze++; 2766 __raise_softirq_irqoff(NET_RX_SOFTIRQ); 2767 goto out; 2768 } 2769 |
