Re: [PATCH net v2 3/4] bnxt: make sure xmit_more + errors does not miss doorbells

[Michael Chan <michael.chan@broadcom.com>]

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On Wed, Aug 11, 2021 at 2:38 PM Jakub Kicinski <kuba@kernel.org> wrote:

> @@ -396,6 +404,8 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
>         free_size = bnxt_tx_avail(bp, txr);
>         if (unlikely(free_size < skb_shinfo(skb)->nr_frags + 2)) {
>                 netif_tx_stop_queue(txq);
> +               if (net_ratelimit() && txr->kick_pending)
> +                       netif_warn(bp, tx_err, dev, "bnxt: ring busy!\n");

I think there is one more problem here.  Now that it is possible to
get here, we can race with bnxt_tx_int() again here.  We can call
netif_tx_stop_queue() here after bnxt_tx_int() has already cleaned the
entire TX ring.  So I think we need to call bnxt_tx_wake_queue() here
again if descriptors have become available.

>                 return NETDEV_TX_BUSY;
>         }
>

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