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

On 2021-08-13 15:25, Ikjoon Jang wrote:

Hi,

On Fri, Aug 13, 2021 at 10:44 AM Tao Wang [off-list ref] wrote:

quoted

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 <redacted>
---
 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.

quoted

        }
        return 0;
 }
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