Re: [PATCH bpf v3] xdp: fix hang while unregistering device bound to xdp socket

[William Tu]

On Mon, Jun 10, 2019 at 9:39 AM Ilya Maximets <i.maximets@xxxxxxxxxxx> wrote:
>
> Device that bound to XDP socket will not have zero refcount until the
> userspace application will not close it. This leads to hang inside
> 'netdev_wait_allrefs()' if device unregistering requested:
>
>   # ip link del p1
>   < hang on recvmsg on netlink socket >
>
>   # ps -x | grep ip
>   5126  pts/0    D+   0:00 ip link del p1
>
>   # journalctl -b
>
>   Jun 05 07:19:16 kernel:
>   unregister_netdevice: waiting for p1 to become free. Usage count = 1
>
>   Jun 05 07:19:27 kernel:
>   unregister_netdevice: waiting for p1 to become free. Usage count = 1
>   ...

Thanks. I hit the same issue quite often when using veth driver to
test AF_XDP.

>
> Fix that by implementing NETDEV_UNREGISTER event notification handler
> to properly clean up all the resources and unref device.
>
> This should also allow socket killing via ss(8) utility.
>
> Fixes: 965a99098443 ("xsk: add support for bind for Rx")
> Signed-off-by: Ilya Maximets <i.maximets@xxxxxxxxxxx>
> ---
Tested-by: William Tu <u9012063@xxxxxxxxx>