Christian Lamparter wrote:
> well, I took a quick look into the usb code...
> (I know this isn't "usb_poison_anchored_urbs", or usb_kill_anchored_urbs,
> but they have to use this ones!)
>
> void usb_kill_urb(struct urb *urb)
> {
> might_sleep();
> if (!(urb && urb->dev && urb->ep))
> return;
> atomic_inc(&urb->reject);
>
> usb_hcd_unlink_urb(urb, -ENOENT);
> wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
>
> atomic_dec(&urb->reject);
> }
>
> vs.
>
> void usb_poison_urb(struct urb *urb)
> {
> might_sleep();
> if (!(urb && urb->dev && urb->ep))
> return;
> atomic_inc(&urb->reject);
>
> usb_hcd_unlink_urb(urb, -ENOENT);
> wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
> }
>
> it looks like usb_poison_urb doesn't do what I though it does...
> In fact the way I see it now... there's no advantage if we use it,
> we can stick usb_kill_anchored_urb, right?
the difference is that after an urb is killed it can be resubmitted;
after it's poisoned it will always fail w/ -EPERM.
usb_poison_anchored_urbs() will not only poison all anchored urbs
but also mark the anchor itself -- and the usb_anchor_urb() call will
then also poison every urb it anchors.
So once you have called usb_poison_anchored_urbs(A), you can count
on every single urb that either already was or is subsequently
anchored to A to always fail on submission.
And any urbs that were already submitted at the time of the
usb_poison_anchored_urbs(A) call will have gone through the completion.
artur
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