Re: [PATCH] usb: xhci-ring: set all cancelled_td's cancel_status to TD_CLEARING_CACHE

[wat]

On 2021-08-13 15:25, Ikjoon Jang wrote:
> Hi,
>
> On Fri, Aug 13, 2021 at 10:44 AM Tao Wang <wat@xxxxxxxxxxxxxx> wrote:
> > USB SSD may fail to unmount if disconnect during data transferring.
> >
> > it stuck in usb_kill_urb() due to urb use_count will not become zero,
> > this means urb giveback is not happen.
> > in xhci_handle_cmd_set_deq() will giveback urb if td's cancel_status
> > equal to TD_CLEARING_CACHE,
> > but in xhci_invalidate_cancelled_tds(), only last canceled td's
> > cancel_status change to TD_CLEARING_CACHE,
> > thus giveback only happen to last urb.
> >
> > this change set all cancelled_td's cancel_status to TD_CLEARING_CACHE
> > rather than the last one, so all urb can giveback.
> >
> > Signed-off-by: Tao Wang <wat@xxxxxxxxxxxxxx>
> > ---
> >  drivers/usb/host/xhci-ring.c | 24 ++++++++++++------------
> >  1 file changed, 12 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/usb/host/xhci-ring.c 
> > b/drivers/usb/host/xhci-ring.c
> > index 8fea44b..c7dd7c0 100644
> > --- a/drivers/usb/host/xhci-ring.c
> > +++ b/drivers/usb/host/xhci-ring.c
> > @@ -960,19 +960,19 @@ static int xhci_invalidate_cancelled_tds(struct 
> > xhci_virt_ep *ep)
> >                         td_to_noop(xhci, ring, td, false);
> >                         td->cancel_status = TD_CLEARED;
> >                 }
> > -       }
> > -       if (cached_td) {
> > -               cached_td->cancel_status = TD_CLEARING_CACHE;
> > -
> > -               err = xhci_move_dequeue_past_td(xhci, slot_id, 
> > ep->ep_index,
> > -                                               
> > cached_td->urb->stream_id,
> > -                                               cached_td);
> > -               /* Failed to move past cached td, try just setting it 
> > noop */
> > -               if (err) {
> > -                       td_to_noop(xhci, ring, cached_td, false);
> > -                       cached_td->cancel_status = TD_CLEARED;
> > +               if (cached_td) {
> > +                       cached_td->cancel_status = TD_CLEARING_CACHE;
> > +
> > +                       err = xhci_move_dequeue_past_td(xhci, slot_id, 
> > ep->ep_index,
> > +                                                       
> > cached_td->urb->stream_id,
> > +                                                       cached_td);
> > +                       /* Failed to move past cached td, try just 
> > setting it noop */
> > +                       if (err) {
> > +                               td_to_noop(xhci, ring, cached_td, 
> > false);
> > +                               cached_td->cancel_status = TD_CLEARED;
> > +                       }
> > +                       cached_td = NULL;
> >                 }
> > -               cached_td = NULL;
>
> I think we can call xhci_move_dequeue_past_td() just once to
> the last halted && cancelled TD in a ring.
>
> But that might need to compare two TDs to see which one is
> the latter, I'm not sure how to do this well. :-/
>
> if (!cached_td || cached_td < td)
>   cached_td = td;

thanks, I think you are correct that we can call 
xhci_move_dequeue_past_td() just once to
 the last halted && cancelled TD in a ring,
but the set status "cached_td->cancel_status = TD_CLEARING_CACHE;" 
should be every cancelled TD.
I am not very good at td and ring, I have a question why we need to
compare two TDs to see which one is the latter.

> >         }
> >         return 0;
> >  }
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
> > Forum,
> > a Linux Foundation Collaborative Project