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

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Date:   Fri, 13 Aug 2021 15:25:12 +0800
From:   Ikjoon Jang <ikjn@...omium.org>
To:     Tao Wang <wat@...eaurora.org>
Cc:     Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "open list:USB XHCI DRIVER" <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: xhci-ring: set all cancelled_td's cancel_status to TD_CLEARING_CACHE

Hi,

On Fri, Aug 13, 2021 at 10:44 AM Tao Wang <wat@...eaurora.org> 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@...eaurora.org>
> ---
>  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;

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