On Fri, Jun 18, 2021 at 04:39:56PM +0300, Prabhakar Kushwaha wrote:

dev_get_by_name() finds network device by name but it also increases
reference count.
Increasing the ref count,
If nvme-tcp queue is present and the network device driver is removed
before nvme_tcp, we will face the following continuous log:
  "kernel:unregister_netdevice: waiting for <eth> to become
  free. Usage count = 2"
And rmmod further halts. Similar case arises during reboot/shutdown
with nvme-tcp queue present and both never completes.

As a fix we will use __dev_get_by_name() which find network device by
name without increasing any reference counter.

And when you remove it without the refcount we'll now have a stale
kernel pointer?

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