On Fri, Aug 16, 2024 at 11:24:00AM +0200, Kurt Kanzenbach wrote:
> From: Sriram Yagnaraman <sriram.yagnaraman@xxxxxxxx>
>
> Always call igb_xdp_ring_update_tail() under __netif_tx_lock(), add a
> comment to indicate that. This is needed to share the same TX ring between
> XDP, XSK and slow paths.
Sorry for being a-hole here but I think this should go to -net as a fix...
I should have brought it up earlier, current igb XDP support is racy on
tail updates which you're fixing here.
Do you agree...or not?:)
>
> Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@xxxxxxxx>
> [Kurt: Split patches]
> Signed-off-by: Kurt Kanzenbach <kurt@xxxxxxxxxxxxx>
> ---
> drivers/net/ethernet/intel/igb/igb_main.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index 11be39f435f3..4d5e5691c9bd 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -2914,6 +2914,7 @@ static int igb_xdp(struct net_device *dev, struct netdev_bpf *xdp)
> }
> }
>
> +/* This function assumes __netif_tx_lock is held by the caller. */
> static void igb_xdp_ring_update_tail(struct igb_ring *ring)
> {
> /* Force memory writes to complete before letting h/w know there
> @@ -3000,11 +3001,11 @@ static int igb_xdp_xmit(struct net_device *dev, int n,
> nxmit++;
> }
>
> - __netif_tx_unlock(nq);
> -
> if (unlikely(flags & XDP_XMIT_FLUSH))
> igb_xdp_ring_update_tail(tx_ring);
>
> + __netif_tx_unlock(nq);
> +
> return nxmit;
> }
>
> @@ -8853,12 +8854,14 @@ static void igb_put_rx_buffer(struct igb_ring *rx_ring,
>
> static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
> {
> + unsigned int total_bytes = 0, total_packets = 0;
> struct igb_adapter *adapter = q_vector->adapter;
> struct igb_ring *rx_ring = q_vector->rx.ring;
> - struct sk_buff *skb = rx_ring->skb;
> - unsigned int total_bytes = 0, total_packets = 0;
> u16 cleaned_count = igb_desc_unused(rx_ring);
> + struct sk_buff *skb = rx_ring->skb;
> + int cpu = smp_processor_id();
> unsigned int xdp_xmit = 0;
> + struct netdev_queue *nq;
> struct xdp_buff xdp;
> u32 frame_sz = 0;
> int rx_buf_pgcnt;
> @@ -8986,7 +8989,10 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
> if (xdp_xmit & IGB_XDP_TX) {
> struct igb_ring *tx_ring = igb_xdp_tx_queue_mapping(adapter);
>
> + nq = txring_txq(tx_ring);
> + __netif_tx_lock(nq, cpu);
> igb_xdp_ring_update_tail(tx_ring);
> + __netif_tx_unlock(nq);
> }
>
> u64_stats_update_begin(&rx_ring->rx_syncp);
>
> --
> 2.39.2
>
