设备关闭操作主要完成设备启用标记位的清除，未发送完的数据发送完，发送禁用通知等操作；下面为相关函数的调用关系，其中dev_change_flags调用__dev_close的流程，已经在设备开启文章中做过介绍，此处不再分析；
1 /** 2 * 设备禁用函数调用关系 3 * dev_change_flags-->_dev_change_flags-->__dev_close 4 * dev_close-->dev_close_many-->__dev_close_many 5 */
dev_close将设备加入到临时链表中，并且调用关闭多个设备的函数，对设备执行关闭操作；
1 /* 设备关闭 */ 2 int dev_close(struct net_device *dev) 3 { 4 /* 启动状态 */ 5 if (dev->flags & IFF_UP) { 6 7 /* 初始化single链表 */ 8 LIST_HEAD(single); 9 /* 加入single链表 */ 10 list_add(&dev->close_list, &single); 11 12 /* 关闭设备 */ 13 dev_close_many(&single, true); 14 15 /* 删除链表 */ 16 list_del(&single); 17 } 18 return 0; 19 }
dev_close_many函数会移除未运行的设备，然后调用__dev_close_many对设备进行关闭，关闭成功之后发送设备关闭消息，并移除关闭设备节点；
1 /* 关闭设备 */ 2 int dev_close_many(struct list_head *head, bool unlink) 3 { 4 struct net_device *dev, *tmp; 5 6 /* Remove the devices that don't need to be closed */ 7 /* 移除未运行的设备 */ 8 list_for_each_entry_safe(dev, tmp, head, close_list) 9 if (!(dev->flags & IFF_UP)) 10 list_del_init(&dev->close_list); 11 12 /* 关闭设备 */ 13 __dev_close_many(head); 14 15 list_for_each_entry_safe(dev, tmp, head, close_list) { 16 /* netlink消息 */ 17 rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING, GFP_KERNEL); 18 19 /* 通知设备关闭 */ 20 call_netdevice_notifiers(NETDEV_DOWN, dev); 21 22 /* 移除设备节点 */ 23 if (unlink) 24 list_del_init(&dev->close_list); 25 } 26 27 return 0; 28 }
__dev_close_many通知设备正在关闭，等待未发送完的数据发送完，如果设备驱动实现了关闭操作函数，则调用之，最后清除开启标记；
1 static int __dev_close_many(struct list_head *head) 2 { 3 struct net_device *dev; 4 5 ASSERT_RTNL(); 6 might_sleep(); 7 8 list_for_each_entry(dev, head, close_list) { 9 /* Temporarily disable netpoll until the interface is down */ 10 /* 禁用netpoll */ 11 netpoll_poll_disable(dev); 12 13 /* 通知设备正在关闭 */ 14 call_netdevice_notifiers(NETDEV_GOING_DOWN, dev); 15 16 /* 清除start标志位 */ 17 clear_bit(__LINK_STATE_START, &dev->state); 18 19 /* Synchronize to scheduled poll. We cannot touch poll list, it 20 * can be even on different cpu. So just clear netif_running(). 21 * 22 * dev->stop() will invoke napi_disable() on all of it's 23 * napi_struct instances on this device. 24 */ 25 smp_mb__after_atomic(); /* Commit netif_running(). */ 26 } 27 28 /* 未发送完的数据发送完 */ 29 dev_deactivate_many(head); 30 31 list_for_each_entry(dev, head, close_list) { 32 const struct net_device_ops *ops = dev->netdev_ops; 33 34 /* 35 * Call the device specific close. This cannot fail. 36 * Only if device is UP 37 * 38 * We allow it to be called even after a DETACH hot-plug 39 * event. 40 */ 41 /* 调用设备关闭操作 */ 42 if (ops->ndo_stop) 43 ops->ndo_stop(dev); 44 45 /* 标记设备关闭 */ 46 dev->flags &= ~IFF_UP; 47 /* 启用netpoll */ 48 netpoll_poll_enable(dev); 49 } 50 51 return 0; 52 }