Subject: Re: [PATCH net-next v7 3/3] net: axienet: Introduce dmaengine support

From: Jakub Kicinski <[email-masked]>
Date: Mon, 9 Oct 2023 17:17:56 -0700

On Mon, 9 Oct 2023 19:41:35 +0000 Pandey, Radhey Shyam wrote:
> > But somewhere else or just here after printing the warning?  
> 
> There is call to netif_stop_queue(ndev) just before this netdev_warn.
> I copied below for quick reference.
> 
> +	sg_len = skb_shinfo(skb)->nr_frags + 1;
> +	if (!CIRC_SPACE(lp->tx_ring_head, lp->tx_ring_tail, TX_BD_NUM_MAX)) {
> +		netif_stop_queue(ndev);
> +		if (net_ratelimit())
> +			netdev_warn(ndev, "TX ring unexpectedly full\n");
> +		return NETDEV_TX_BUSY;
> +	}
> 
> However, I noticed above check doesn't account for all frags - so will 
> modify the if check to see if available space is less than sg_len. If yes, then 
> stop the queue and return busy , else continue with xmit.

Please take a look at:

https://www.kernel.org/doc/html/next/networking/driver.html#stop-queues-in-advance