On Mon, Mar 26, 2018 at 01:14:47PM +0300, Felipe Balbi wrote:
> This is a requirement which has always existed but, somehow, wasn't
> reflected in the documentation and problems weren't found until now
> when Tuba Yavuz found a possible deadlock happening between dwc3 and
> f_hid. She described the situation as follows:
>
> spin_lock_irqsave(&hidg->write_spinlock, flags); // first acquire
> /* we our function has been disabled by host */
> if (!hidg->req) {
> free_ep_req(hidg->in_ep, hidg->req);
> goto try_again;
> }
>
> [...]
>
> status = usb_ep_queue(hidg->in_ep, hidg->req, GFP_ATOMIC);
> =>
> [...]
> => usb_gadget_giveback_request
> =>
> f_hidg_req_complete
> =>
> spin_lock_irqsave(&hidg->write_spinlock, flags); // second acquire
>
> Note that this happens because dwc3 would call ->complete() on a
> failed usb_ep_queue() due to failed Start Transfer command. This is,
> anyway, a theoretical situation because dwc3 currently uses "No
> Response Update Transfer" command for Bulk and Interrupt endpoints.
>
> It's still good to make this case impossible to happen even if the "No
> Reponse Update Transfer" command is changed.
>
> Reported-by: Tuba Yavuz <tuba@xxxxxxxxxxx>
> Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
> Cc: stable <stable@xxxxxxxxxxxxxxx>
> ---
>
> Greg, if you want to pick these two patches as they are, please go
> ahead. If you want, I can also add a Cc stable tag, your call.
I've added the stable tag and applied both of these patches now.
thanks,
greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
