Could you please clarify where exactly do I need to use rtnl lock?
From what I understand, netif_carrier_on/off can be called without the lock.

On Thu, Aug 26, 2021 at 8:15 PM Stephen Hemminger <
stephen@networkplumber.org> wrote:

On Thu, 26 Aug 2021 18:19:09 +0300
Igor Ryzhov [off-list ref] wrote:

quoted

+static int
+kni_ioctl_link(struct net *net, uint32_t ioctl_num,
+             unsigned long ioctl_param)
+{
+     struct kni_net *knet = net_generic(net, kni_net_id);
+     int ret = -EINVAL;
+     struct kni_dev *dev, *n;
+     struct rte_kni_link_info link_info;
+     struct net_device *netdev;
+
+     if (_IOC_SIZE(ioctl_num) > sizeof(link_info))
+             return -EINVAL;
+
+     if (copy_from_user(&link_info, (void *)ioctl_param,

sizeof(link_info)))

quoted

+             return -EFAULT;
+
+     if (strlen(link_info.name) == 0)
+             return -EINVAL;
+
+     down_read(&knet->kni_list_lock);
+     list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
+             if (strncmp(dev->name, link_info.name, RTE_KNI_NAMESIZE)

!= 0)

quoted

+                     continue;
+
+             netdev = dev->net_dev;
+
+             if (link_info.status) {
+                     netif_carrier_on(netdev);
+
+                     dev->speed = link_info.speed;
+                     dev->duplex = link_info.duplex;
+                     dev->autoneg = link_info.autoneg;
+             } else {
+                     netif_carrier_off(netdev);
+             }
+
+             ret = 0;
+             break;
+     }
+     up_read(&knet->kni_list_lock);
+
+     return ret;
+}
+

You need to be using the RTNL mutex in KNI here (and probably elsewhere).
The use of semaphore for list lock should also be replaced by a mutex.

The KNI driver was written long ago and was never reviewed by people
knowledgeable about kernel networking. That is one reason IMHO KNI
should not be used in production systems.