Re: [PATCH net] xsk: correct tx_ring_empty_descs count statistics

[Stanislav Fomichev <stfomichev@gmail.com>]

On 03/29, Wang Liang wrote:
> The tx_ring_empty_descs count may be incorrect, when set the XDP_TX_RING
> option but do not reserve tx ring. Because xsk_poll() try to wakeup the
> driver by calling xsk_generic_xmit() for non-zero-copy mode. So the
> tx_ring_empty_descs count increases once the xsk_poll()is called:
> 
>   xsk_poll
>     xsk_generic_xmit
>       __xsk_generic_xmit
>         xskq_cons_peek_desc
>           xskq_cons_read_desc
>             q->queue_empty_descs++;
> 
> To avoid this count error, add check for tx descs before send msg in poll.
> 
> Fixes: df551058f7a3 ("xsk: Fix crash in poll when device does not support ndo_xsk_wakeup")
> Signed-off-by: Wang Liang <wangliang74@huawei.com>

Acked-by: Stanislav Fomichev <sdf@fomichev.me>