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

wat
2021-08-13T08:44:44Z

On 2021-08-13 15:25, Ikjoon Jang wrote:
> Hi,
>
> On Fri, Aug 13, 2021 at 10:44 AM Tao Wang <wat@codeaurora.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@codeaurora.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;
>

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
>>