Matthias Fuchs wrote:
> But I ran into some issues. Perhaps some of you can help:
> Q1: Under high TX load the driver runs out of free tx_contexts.
> (see "couldn't find free context"). I expected the socket can core
> to take care of this so that the lower driver cannot be overrun
> by tx jobs. Either this expectation is wrong or there's a bug in
> the driver :-)
Hi Matthias,
i wonder, why you do not stop the netdev tx queue immediately at the beginning
of
> +static netdev_tx_t esd_usb2_start_xmit(struct sk_buff *skb,
> + struct net_device *netdev)
but at this (late) point:
> + if (err) {
> + can_free_echo_skb(netdev, context->echo_index);
> +
> + atomic_dec(&priv->active_tx_urbs);
> + usb_unanchor_urb(urb);
> +
> + if (err == -ENODEV)
> + netif_device_detach(netdev);
> + else
> + dev_warn(ND2D(netdev), "failed tx_urb %d\n", err);
> +
> + goto releasebuf;
> + } else {
> + netdev->trans_start = jiffies;
> +
> + /* Slow down tx path */
> + if (atomic_read(&priv->active_tx_urbs) >= MAX_TX_URBS)
> + netif_stop_queue(netdev);
> + }
The netdev queues in Linux will give you skbs until you say 'stop' :-)
This is not SocketCAN specific.
I assume the handling of netif_[wake|stop]_queue() should be reworked.
E.g. invoke netif_stop_queue() at the beginning of esd_usb2_start_xmit() and
when everything is really fine, you can invoke netif_wake_queue() at the and
of esd_usb2_start_xmit() again.
Btw. did you check the above code with
if (atomic_read(&priv->active_tx_urbs) >= MAX_TX_URBS - 1)
to test for an off-by-one problem in the tx_urbs?
Regards,
Oliver
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