Hi Oliver,
On Mon, Aug 06, 2012 at 10:10:43AM +0200, Oliver Neukum wrote:
> On Monday 06 August 2012 07:21:29 Olivier Sobrie wrote:
> > This driver provides support for several Kvaser CAN/USB devices.
> > Such kind of devices supports up to three can network interfaces.
> >
> > It has been tested with a Kvaser USB Leaf Light (one network interface)
> > connected to a pch_can interface.
> > The firmware version of the Kvaser device was 2.5.205.
>
> > +static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb,
> > + struct net_device *netdev)
> > +{
> > + struct kvaser_usb_net_priv *priv = netdev_priv(netdev);
> > + struct kvaser_usb *dev = priv->dev;
> > + struct net_device_stats *stats = &netdev->stats;
> > + struct can_frame *cf = (struct can_frame *)skb->data;
> > + struct kvaser_usb_tx_urb_context *context = NULL;
> > + struct urb *urb;
> > + void *buf;
> > + struct kvaser_msg *msg;
> > + int i, err;
> > + int ret = NETDEV_TX_OK;
> > +
> > + if (can_dropped_invalid_skb(netdev, skb))
> > + return NETDEV_TX_OK;
> > +
> > + urb = usb_alloc_urb(0, GFP_ATOMIC);
> > + if (!urb) {
> > + netdev_err(netdev, "No memory left for URBs\n");
> > + stats->tx_dropped++;
> > + dev_kfree_skb(skb);
> > + return NETDEV_TX_OK;
> > + }
> > +
> > + buf = usb_alloc_coherent(dev->udev, sizeof(struct kvaser_msg),
> > + GFP_ATOMIC, &urb->transfer_dma);
>
> usb_alloc_coherent() as a rule only makes sense if you reuse the buffer
> and in some cases not even then. Please use a simple kmalloc()
Ok thanks. I'll change it.
>
> > + if (!buf) {
> > + netdev_err(netdev, "No memory left for USB buffer\n");
> > + stats->tx_dropped++;
> > + dev_kfree_skb(skb);
> > + goto nobufmem;
> > + }
> > +
> > + msg = (struct kvaser_msg *)buf;
> > + msg->len = MSG_HEADER_LEN + sizeof(struct kvaser_msg_tx_can);
> > + msg->u.tx_can.flags = 0;
> > + msg->u.tx_can.channel = priv->channel;
> > +
> > + if (cf->can_id & CAN_EFF_FLAG) {
> > + msg->id = CMD_TX_EXT_MESSAGE;
> > + msg->u.tx_can.msg[0] = (cf->can_id >> 24) & 0x1f;
> > + msg->u.tx_can.msg[1] = (cf->can_id >> 18) & 0x3f;
> > + msg->u.tx_can.msg[2] = (cf->can_id >> 14) & 0x0f;
> > + msg->u.tx_can.msg[3] = (cf->can_id >> 6) & 0xff;
> > + msg->u.tx_can.msg[4] = cf->can_id & 0x3f;
> > + } else {
> > + msg->id = CMD_TX_STD_MESSAGE;
> > + msg->u.tx_can.msg[0] = (cf->can_id >> 6) & 0x1f;
> > + msg->u.tx_can.msg[1] = cf->can_id & 0x3f;
> > + }
> > +
> > + msg->u.tx_can.msg[5] = cf->can_dlc;
> > + memcpy(&msg->u.tx_can.msg[6], cf->data, cf->can_dlc);
> > +
> > + if (cf->can_id & CAN_RTR_FLAG)
> > + msg->u.tx_can.flags |= MSG_FLAG_REMOTE_FRAME;
> > +
> > + for (i = 0; i < ARRAY_SIZE(priv->tx_contexts); i++) {
> > + if (priv->tx_contexts[i].echo_index == MAX_TX_URBS) {
> > + context = &priv->tx_contexts[i];
> > + break;
> > + }
> > + }
> > +
> > + if (!context) {
> > + netdev_warn(netdev, "cannot find free context\n");
> > + ret = NETDEV_TX_BUSY;
> > + goto releasebuf;
> > + }
> > +
> > + context->priv = priv;
> > + context->echo_index = i;
> > + context->dlc = cf->can_dlc;
> > +
> > + msg->u.tx_can.tid = context->echo_index;
> > +
> > + usb_fill_bulk_urb(urb, dev->udev,
> > + usb_sndbulkpipe(dev->udev,
> > + dev->bulk_out->bEndpointAddress),
> > + buf, msg->len,
> > + kvaser_usb_write_bulk_callback, context);
> > + urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
> > + usb_anchor_urb(urb, &priv->tx_submitted);
> > +
> > + can_put_echo_skb(skb, netdev, context->echo_index);
> > +
> > + atomic_inc(&priv->active_tx_urbs);
> > +
> > + if (atomic_read(&priv->active_tx_urbs) >= MAX_TX_URBS)
> > + netif_stop_queue(netdev);
> > +
> > + err = usb_submit_urb(urb, GFP_ATOMIC);
> > + if (unlikely(err)) {
> > + can_free_echo_skb(netdev, context->echo_index);
> > +
> > + atomic_dec(&priv->active_tx_urbs);
> > + usb_unanchor_urb(urb);
> > +
> > + stats->tx_dropped++;
> > +
> > + if (err == -ENODEV)
> > + netif_device_detach(netdev);
> > + else
> > + netdev_warn(netdev, "Failed tx_urb %d\n", err);
> > +
> > + goto releasebuf;
> > + }
> > +
> > + netdev->trans_start = jiffies;
> > +
> > + usb_free_urb(urb);
> > +
> > + return NETDEV_TX_OK;
> > +
> > +releasebuf:
> > + usb_free_coherent(dev->udev, sizeof(struct kvaser_msg),
> > + buf, urb->transfer_dma);
> > +nobufmem:
> > + usb_free_urb(urb);
> > + return ret;
> > +}
>
> > +static int kvaser_usb_init_one(struct usb_interface *intf,
> > + const struct usb_device_id *id, int channel)
> > +{
> > + struct kvaser_usb *dev = usb_get_intfdata(intf);
> > + struct net_device *netdev;
> > + struct kvaser_usb_net_priv *priv;
> > + int i, err;
> > +
> > + netdev = alloc_candev(sizeof(*priv), MAX_TX_URBS);
> > + if (!netdev) {
> > + dev_err(&intf->dev, "Cannot alloc candev\n");
> > + return -ENOMEM;
> > + }
> > +
> > + priv = netdev_priv(netdev);
> > +
> > + init_completion(&priv->start_comp);
> > + init_completion(&priv->stop_comp);
> > +
> > + init_usb_anchor(&priv->tx_submitted);
> > + atomic_set(&priv->active_tx_urbs, 0);
> > +
> > + for (i = 0; i < ARRAY_SIZE(priv->tx_contexts); i++)
> > + priv->tx_contexts[i].echo_index = MAX_TX_URBS;
> > +
> > + priv->dev = dev;
> > + priv->netdev = netdev;
> > + priv->channel = channel;
> > +
> > + priv->can.state = CAN_STATE_STOPPED;
> > + priv->can.clock.freq = CAN_USB_CLOCK;
> > + priv->can.bittiming_const = &kvaser_usb_bittiming_const;
> > + priv->can.do_set_bittiming = kvaser_usb_set_bittiming;
> > + priv->can.do_set_mode = kvaser_usb_set_mode;
> > + priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES;
> > + if (id->driver_info & KVASER_HAS_SILENT_MODE)
> > + priv->can.ctrlmode_supported |= CAN_CTRLMODE_LISTENONLY;
> > +
> > + netdev->flags |= IFF_ECHO;
> > +
> > + netdev->netdev_ops = &kvaser_usb_netdev_ops;
> > +
> > + SET_NETDEV_DEV(netdev, &intf->dev);
> > +
> > + err = register_candev(netdev);
> > + if (err) {
> > + dev_err(&intf->dev, "Failed to register can device\n");
> > + free_candev(netdev);
> > + return err;
> > + }
> > +
>
> Here the device is usable.
>
> > + dev->nets[channel] = priv;
>
> And only know you init this field. Looks like a race condition.
Argh... Indeed.
Thanks
>
> > + netdev_dbg(netdev, "device registered\n");
> > +
> > + return 0;
> > +}
> > +
>
> > +static void kvaser_usb_disconnect(struct usb_interface *intf)
> > +{
> > + struct kvaser_usb *dev = usb_get_intfdata(intf);
> > + int i;
> > +
> > + usb_set_intfdata(intf, NULL);
> > +
> > + if (!dev)
> > + return;
> > +
> > + for (i = 0; i < dev->nchannels; i++) {
> > + if (!dev->nets[i])
> > + continue;
> > +
> > + unregister_netdev(dev->nets[i]->netdev);
> > + free_candev(dev->nets[i]->netdev);
> > + }
> > +
> > + kvaser_usb_unlink_all_urbs(dev);
>
> So what happens if an URB completes between freeing the candev
> and unlinking and proceeds to push data to upper layers?
In this case I should avoid using netdev context, i.e. pointer to "struct
kvaser_usb_net_priv" in urb callbacks.
Is that what you mean?
I see it is well done in kvaser_usb_read_bulk_callback()
but not in kvaser_usb_write_bulk_callback().
I'll better protect the callbacks and move the free_candev after the
unlink.
Thank you,
--
Olivier
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