linux linkwatch进程指的是什么
链接状态改变(linkwatch)
在Linux网络协议栈中linkwatch模块用来通知网卡当前是否能够进行数据传输.
驱动中调用netif_carrier_on/netif_carrier_off函数来通知网络状态变化.
主要作用:
启动/禁止 TX队列的流量控制功能
发起netlink消息NETDEV_CHANGE到用户空间
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | void netif_carrier_on(struct net_device *dev){ if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) { if (dev->reg_state == NETREG_UNINITIALIZED) return; linkwatch_fire_event(dev); if (netif_running(dev)) __netdev_watchdog_up(dev); }}void netif_carrier_off(struct net_device *dev){ if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state)) { if (dev->reg_state == NETREG_UNINITIALIZED) return ; linkwatch_fire_event(dev); }}linwatch模块，只需要知道状态改变了，不需要知道具体是on还是offvoid linkwatch_fire_event(struct net_device *dev){ /*判断是否为紧急事件, 内核规定两次事件的间隔至少为1个HZ*/ bool urgent = linkwatch_urgent_event(dev); if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) { linkwatch_add_event(dev);//把dev添加到lweventlist链表 } else if (!urgent) return; /*调用工作队列linkwatch_event */ linkwatch_schedule_work(urgent);} static void __linkwatch_run_queue(int urgent_only){ struct net_device *dev; LIST_HEAD(wrk); while (!list_empty(&wrk)) { dev = list_first_entry(&wrk, struct net_device, link_watch_list); list_del_init(&dev->link_watch_list); /*判断是否只执行紧急事件 */ if (urgent_only && !linkwatch_urgent_event(dev)) { list_add_tail(&dev->link_watch_list, &lweventlist); continue; } spin_unlock_irq(&lweventlist_lock); linkwatch_do_dev(dev); spin_lock_irq(&lweventlist_lock); } if (!list_empty(&lweventlist)){ linkwatch_schedule_work(0); } spin_unlock_irq(&lweventlist_lock);} static void linkwatch_do_dev(struct net_device *dev){ rfc2863_policy(dev); if (dev->flags & IFF_UP) { if (netif_carrier_ok(dev)) dev_activate(dev);//启动tx队列流量控制功能 else dev_deactivate(dev)；//禁止tx队列流量控制功能 netdev_state_change(dev);//发起Netlink事件:NETDEV_CHANGE } dev_put(dev);} |
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