Am Dienstag, 27. Juni 2006 16:09 schrieb Franck Bui-Huu:
> Oliver Neukum wrote:
> > Am Dienstag, 27. Juni 2006 09:52 schrieb Franck Bui-Huu:
> >> + expire = timeout ? msecs_to_jiffies(timeout) :
> >> MAX_SCHEDULE_TIMEOUT;
> >> + if (!wait_for_completion_timeout(&done, expire)) {
> >> + usb_unlink_urb(urb);
> >> }
> >> -
> >> + status = urb->status;
> >
> > Hm, is this racy?
> > What happens if usb_unlink_urb() and the completion handler race?
> > If usb_unlink_urb() fails to unlink the URB because it is too late,
> > is it guaranteed that urb->status is valid?
> > In the old version this could not happen because the completion was
> > always done.
>
> well, I'm not sure to understand. Do you mean "what happen if the timeout has
> expired, but just before calling usb_unlink_urb() the urb is completed by the
> hcd" ?
>
> If so, I think that usb_unlink_urb() handles this case by checking (with lock
> held) that the urb is still queued.
Precisely. If the URB is not queued it'll notice. But you read urb->status
even in that case.
Regards
Oliver
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