netdev - Re: [PATCH net] ice: don't stop netdev tx queues when setting up XSK socket

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Date: Mon, 25 Sep 2023 15:58:26 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Tony Nguyen <anthony.l.nguyen@...el.com>, <davem@...emloft.net>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <edumazet@...gle.com>,
	<netdev@...r.kernel.org>
CC: Kamil Maziarz <kamil.maziarz@...el.com>, <maciej.fijalkowski@...el.com>,
	<magnus.karlsson@...el.com>, <ast@...nel.org>, <daniel@...earbox.net>,
	<hawk@...nel.org>, <john.fastabend@...il.com>, <bpf@...r.kernel.org>, Chandan
 Kumar Rout <chandanx.rout@...el.com>
Subject: Re: [PATCH net] ice: don't stop netdev tx queues when setting up XSK
 socket



On 9/25/2023 10:19 AM, Tony Nguyen wrote:
> From: Kamil Maziarz <kamil.maziarz@...el.com>
> 
> Avoid stopping netdev tx queues during XSK setup by removing
> netif_tx_stop_queue() and netif_tx_start_queue().
> These changes prevent unnecessary stopping and starting of netdev
> transmit queues during the setup of XDP socket. Without this change,
> after stopping the XDP traffic flow tracker and then stopping
> the XDP prog - NETDEV WATCHDOG transmit queue timed out appears.
> 
> Fixes: 2d4238f55697 ("ice: Add support for AF_XDP")
> Signed-off-by: Kamil Maziarz <kamil.maziarz@...el.com>
> Tested-by: Chandan Kumar Rout <chandanx.rout@...el.com> (A Contingent Worker at Intel)
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
> ---

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

>  drivers/net/ethernet/intel/ice/ice_xsk.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> index 2a3f0834e139..cec492b827d4 100644
> --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> @@ -179,7 +179,6 @@ static int ice_qp_dis(struct ice_vsi *vsi, u16 q_idx)
>  			return -EBUSY;
>  		usleep_range(1000, 2000);
>  	}
> -	netif_tx_stop_queue(netdev_get_tx_queue(vsi->netdev, q_idx));
>  

These were introduced by the original implementation in commit
2d4238f55697 ("ice: Add support for AF_XDP"), without explanation.

Looking at some of the other implementations I don't see calls to
netif_tx_stop_queue or netif_tx_start_queue, so at least its not common.
In fact the only caller in an _xsk.c file appears to be ice.

Thanks,
Jake

>  	ice_fill_txq_meta(vsi, tx_ring, &txq_meta);
>  	err = ice_vsi_stop_tx_ring(vsi, ICE_NO_RESET, 0, tx_ring, &txq_meta);
> @@ -268,7 +267,6 @@ static int ice_qp_ena(struct ice_vsi *vsi, u16 q_idx)
>  	ice_qvec_toggle_napi(vsi, q_vector, true);
>  	ice_qvec_ena_irq(vsi, q_vector);
>  
> -	netif_tx_start_queue(netdev_get_tx_queue(vsi->netdev, q_idx));
>  free_buf:
>  	kfree(qg_buf);
>  	return err;