Hi,
> From: Felipe Balbi, Sent: Monday, May 21, 2018 3:57 PM
>
> Hi,
>
> Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx> writes:
> > The usb_ep_queue() in printer_write() is possible to call req->complete().
> > In that case, since tx_complete() calls list_add(&req->list, &dev->tx_reqs),
> > printer_write() should not call list_add(&req->list, &dev->tx_reqs_active)
> > because the transfer has already finished. So, this patch checks
> > the condition of req->list before adding the list in printer_write().
> >
> > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> > ---
> > This issue can be caused by renesas_usbhs udc driver. I'm not sure
> > this patch is acceptable or not. So, I marked RFC on this patch.
>
> can you explain this a little more? How do you trigger the problem?
Sure. If printer_write() called usb_ep_queue() with 63 bytes or less data,
the renesas_usbhs udc driver transfers data as PIO. In this case, the udc
driver calls usb_gadget_giveback_reuqest() in .queue ops (usbhsg_ep_queue())
immediately. Then, printer_write() calls list_add(&req->list, &dev->tx_reqs_active); wrongly.
After that, if we do rmmod g_printer, WARN_ON(!list_empty(&dev->tx_reqs_active); happens in
printer_func_unbind() because the list entry is not removed.
< Reference: calltrace (very long though...) >
usb_ep_queue(...); at f_printer.c / printer_write()
1-> usbhsg_ep_queue(); at renesas_usbhs/mod_gadget.c
2-> usbhsg_queue_push();
3-> usbhs_pkt_start(); at renesas_usbhs/fifo.c
4-> usbhsf_pkt_handler();
5-> func() = usbhsf_dma_prepare_push();
6-> goto usbhsf_pio_prepare_push; // Because len is 63
7-> usbhsf_pio_prepare_push();
8-> usbhsf_pio_try_push();
5-> done() = usbhsg_queue_done(); at renesas_usbhs/mod_gadget.c
6-> __usbsg_queue_pop();
7-> usb_gadget_giveback_reuqest();
8-> tx_complete(); at f_printer.c
9-> list_del_init(&req->list);
9-> list_add(&req->list, &dev->tx_reqs);
list_add(&req->list, &dev->tx_reqs_active); // Even if the transaction already finished, this driver is possible to add the list to "active".
Best regards,
Yoshihiro Shimoda
> --
> balbi
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