Re: [PATCH net-next v1 3/5] net: lan743x: quiesce TX before freeing the rings

[Nicolai Buchwitz <nb@tipi-net.de>]

On 15.10.2026 17:00, Chris Babroski wrote:
> lan743x_pcidev_shutdown(), which suspend also uses, calls
> netif_device_detach() and then lan743x_netdev_close() with the qdisc
> still attached. Detaching only sets the queue stop bits. It does not 
> wait
> for an ndo_start_xmit() that is already running, and the TX NAPI poll
> still wakes a stopped queue as soon as it has reclaimed descriptors. 
> The
> TX NAPI of a channel that has not been closed yet can therefore restart
> its queue, and the stack then transmits on a ring that
> lan743x_tx_close() is freeing.
> 
> Only wake a queue from TX NAPI while the device is present. In
> lan743x_netdev_close(), wait for any NAPI poll that may have missed the
> detach with synchronize_net(), then stop all queues with
> netif_tx_disable(), which also waits for transmits in progress, before
> closing the channels. For ndo_stop the qdisc is already deactivated, so
> this only adds a grace period there.
> 
> Fixes: 23f0703c125b ("lan743x: Add main source files for new lan743x 
> driver")
> Assisted-by: LLM
> Signed-off-by: Chris Babroski <cbabroski@nvidia.com>
> ---
>  drivers/net/ethernet/microchip/lan743x_main.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/microchip/lan743x_main.c 
> b/drivers/net/ethernet/microchip/lan743x_main.c
> index 583f631df701..8d256a80dac6 100644
> --- a/drivers/net/ethernet/microchip/lan743x_main.c
> +++ b/drivers/net/ethernet/microchip/lan743x_main.c
> @@ -2125,7 +2125,8 @@ static int lan743x_tx_napi_poll(struct 
> napi_struct *napi, int weight)
>  	/* clean up tx ring */
>  	lan743x_tx_release_completed_descriptors(tx);
>  	txq = netdev_get_tx_queue(adapter->netdev, tx->channel_number);
> -	if (netif_tx_queue_stopped(txq)) {
> +	if (netif_tx_queue_stopped(txq) &&
> +	    netif_device_present(adapter->netdev)) {
>  		if (tx->rqd_descriptors) {
>  			if (tx->rqd_descriptors <=
>  			    lan743x_tx_get_avail_desc(tx)) {
> @@ -3336,6 +3337,9 @@ static int lan743x_netdev_close(struct net_device 
> *netdev)
> 
>  	lan743x_phylink_disconnect(adapter);
> 
> +	synchronize_net();
> +	netif_tx_disable(netdev);
> +
>  	for (index = 0; index < adapter->used_tx_channels; index++)
>  		lan743x_tx_close(&adapter->tx[index]);

Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>

Thanks,
Nicolai