Hi Arvid,
On Tue, Apr 10, 2012 at 11:41:24PM +0000, Arvid Brodin wrote:
> On 2012-04-05 14:56, Michael Grzeschik wrote:
> > Its possible that there are RETIRED qtds in the
> > the qtd_list, which have been dequeued. Make sure
> > to iterate through the whole list.
> >
> > This for instance fixes hanging serial devices, which wait
> > for dequeued urbs to properly close their device node.
> >
> > Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
> > ---
> > drivers/usb/host/isp1760-hcd.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/host/isp1760-hcd.c b/drivers/usb/host/isp1760-hcd.c
> > index 6599616..6e0bd48 100644
> > --- a/drivers/usb/host/isp1760-hcd.c
> > +++ b/drivers/usb/host/isp1760-hcd.c
> > @@ -800,7 +800,7 @@ static void collect_qtds(struct usb_hcd *hcd, struct isp1760_qh *qh,
> >
> > list_for_each_entry_safe(qtd, qtd_next, &qh->qtd_list, qtd_list) {
> > if (qtd->status < QTD_XFER_COMPLETE)
> > - break;
> > + continue;
> >
> > last_qtd = last_qtd_of_urb(qtd, qh);
> >
>
> Ok, so this happens when
>
> 1) several urbs are queued to an endpoint
> 2) an urb (not the first in the list) is dequeued
> and
> 3) the device for some reason won't handle/finish the earlier urbs?
Yes, to all three points.
Especially point three is tricky. The caller [1] of usb_kill_urb
triggers a wait_event, which will hang until somebody calls
isp1760_urb_done.
This will only happen when we collect all of the enqueud QTDs
and look for QTDs which have the status QTD_RETIRE.
What is the condition to finish the earlier urb in the queue of an
endpoint? Has the collect_qtds to be in a serial order?
This situation happens reproducible when i try to establish a pppd
connection with my sierra serial usb modem which then does not get a
link. The pppd afterwards hangs while trying to close the ttyUSB
devicenode.
[1] In my special case its: sierra_stop_rx_urbs called by sierra_close.
Cheers,
Michael
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