On Wed, 29 Aug 2012, Sebastian Andrzej Siewior wrote:
> > > The BULK URBs usually don't make a scene. They re-submit the complete
> > > queue length in BH so we have a little time in between. The INTR URB is
> > > more evil because usbnet's intr_complete() causes to re-submitt it
> > > immediately. That means we hardly do any progress and end up in a
> > > busy loop.
> >
> > This sounds like a possible bug in usbnet. If usbnet encounters
> > repeated failures while trying to communicate with a USB device, it
> > shouldn't continue to retry indefinitely. It should eventually give
> > up, and maybe do a device reset.
>
> So to interrupt the intr packets we need atleast
>
> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
> index 8531c1c..8dc3705 100644
> --- a/drivers/net/usb/usbnet.c
> +++ b/drivers/net/usb/usbnet.c
> @@ -194,6 +194,7 @@ static void intr_complete (struct urb *urb)
> /* software-driven interface shutdown */
> case -ENOENT: /* urb killed */
> case -ESHUTDOWN: /* hardware gone */
> + case -EPIPE:
> netif_dbg(dev, ifdown, dev->net,
> "intr shutdown, code %d\n", status);
> return;
No, that's not right. For one thing, the error is -EPROTO, not -EPIPE.
But aside from that, usbnet has a comment a little farther down:
/* NOTE: not throttling like RX/TX, since this endpoint
* already polls infrequently
*/
Corresponding to this, there's a comment in dummy-hcd:
case PIPE_INTERRUPT:
/* FIXME is it urb->interval since the last xfer?
* this almost certainly polls too fast.
*/
So the problem appears to be that dummy-hcd doesn't implement the right
interval for periodic transfers. I'd accept a patch to fix that.
Alan Stern
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