[PATCH v2 1/3] can: rockchip_canfd: prevent TX stall on echo skb failure

[Marc Kleine-Budde]

On 30.07.2026 18:11:46, Cunhao Lu wrote:
> rkcanfd_start_xmit() advances tx_head and requests transmission even when
> can_put_echo_skb() fails. This creates a pending TX entry without the echo
> skb that the RXSTX completion path needs to match the self-received frame.
> The entry cannot be completed, and the netdev TX queue can remain stopped
> after the two-entry software FIFO fills.
>
> Do not advance tx_head or request transmission if the echo skb cannot be
> installed. Account the frame as dropped and report the error. The
> -ENOMEM and -EBUSY paths have already consumed the skb; explicitly free
> it on -EINVAL, where ownership remains with the caller.

Can you update can_put_echo_skb() to always free the skb in the error case?

> Fixes: b6661d73290c ("can: rockchip_canfd: add TX PATH")
> Cc: stable at vger.kernel.org
> Signed-off-by: Cunhao Lu <1579567540 at qq.com>
> ---
>  drivers/net/can/rockchip/rockchip_canfd-tx.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/can/rockchip/rockchip_canfd-tx.c b/drivers/net/can/rockchip/rockchip_canfd-tx.c
> index 12200dcfd338..d2cbe25c46d6 100644
> --- a/drivers/net/can/rockchip/rockchip_canfd-tx.c
> +++ b/drivers/net/can/rockchip/rockchip_canfd-tx.c
> @@ -125,8 +125,18 @@ netdev_tx_t rkcanfd_start_xmit(struct sk_buff *skb, struct net_device *ndev)
>
>  	frame_len = can_skb_get_frame_len(skb);
>  	err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
> -	if (!err)
> -		netdev_sent_queue(priv->ndev, frame_len);
> +	if (err) {
> +		if (err == -EINVAL)
> +			dev_kfree_skb_any(skb);
> +
> +		ndev->stats.tx_dropped++;
> +		if (net_ratelimit())
> +			netdev_err(ndev, "%s: failed to put echo skb: %pe\n",
> +				   __func__, ERR_PTR(err));

Is this error message needed? In the -EINVAL case can_put_echo_skb()
already emits an error. If skb allocation I think in -ENOMEM case the
kernel already throws an error, right?

> +
> +		return NETDEV_TX_OK;
> +	}
> +	netdev_sent_queue(priv->ndev, frame_len);
>
>  	WRITE_ONCE(priv->tx_head, priv->tx_head + 1);

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
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