Subject: Re: [PATCH iwl-net v3 5/6] ice: remove ICE_CFG_BUSY locking from AF_XDP code

From: Maciej Fijalkowski <[email-masked]>
Date: Thu, 22 Aug 2024 13:43:50 +0200

On Mon, Aug 19, 2024 at 12:05:42PM +0200, Larysa Zaremba wrote:
> Locking used in ice_qp_ena() and ice_qp_dis() does pretty much nothing,
> because ICE_CFG_BUSY is a state flag that is supposed to be set in a PF
> state, not VSI one. Therefore it does not protect the queue pair from
> e.g. reset.
> 
> Despite being useless, it still can deadlock the unfortunate functions that
> have fell into the same ICE_CFG_BUSY-VSI trap. This happens if ice_qp_ena
> returns an error.

I believe the last sentence is not valid after our recent fixes around xsk
and tx timeouts.

> 
> Remove ICE_CFG_BUSY locking from ice_qp_dis() and ice_qp_ena().
> 
> Fixes: 2d4238f55697 ("ice: Add support for AF_XDP")
> Reviewed-by: Wojciech Drewek <[email-masked]>
> Reviewed-by: Jacob Keller <[email-masked]>
> Tested-by: Chandan Kumar Rout <[email-masked]>
> Signed-off-by: Larysa Zaremba <[email-masked]>

Reviewed-by: Maciej Fijalkowski <[email-masked]>

> ---
>  drivers/net/ethernet/intel/ice/ice_xsk.c | 9 ---------
>  1 file changed, 9 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> index 8693509efbe7..5dee829bfc47 100644
> --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> @@ -165,7 +165,6 @@ static int ice_qp_dis(struct ice_vsi *vsi, u16 q_idx)
>  	struct ice_q_vector *q_vector;
>  	struct ice_tx_ring *tx_ring;
>  	struct ice_rx_ring *rx_ring;
> -	int timeout = 50;
>  	int fail = 0;
>  	int err;
>  
> @@ -176,13 +175,6 @@ static int ice_qp_dis(struct ice_vsi *vsi, u16 q_idx)
>  	rx_ring = vsi->rx_rings[q_idx];
>  	q_vector = rx_ring->q_vector;
>  
> -	while (test_and_set_bit(ICE_CFG_BUSY, vsi->state)) {
> -		timeout--;
> -		if (!timeout)
> -			return -EBUSY;
> -		usleep_range(1000, 2000);
> -	}
> -
>  	synchronize_net();
>  	netif_carrier_off(vsi->netdev);
>  	netif_tx_stop_queue(netdev_get_tx_queue(vsi->netdev, q_idx));
> @@ -261,7 +253,6 @@ static int ice_qp_ena(struct ice_vsi *vsi, u16 q_idx)
>  		netif_tx_start_queue(netdev_get_tx_queue(vsi->netdev, q_idx));
>  		netif_carrier_on(vsi->netdev);
>  	}
> -	clear_bit(ICE_CFG_BUSY, vsi->state);
>  
>  	return fail;
>  }
> -- 
> 2.43.0
>