Re: [PATCH] usb-host: workaround libusb bug

[BALATON Zoltan]

On Fri, 29 May 2020, Gerd Hoffmann wrote:
> libusb seems to no allways call the completion callback for requests

Typo: not always call.

Regards,
BALATON Zoltan

> canceled (which it is supposed to do according to the docs).  So add
> a limit to avoid qemu waiting forever.
>
> Tested-by: BALATON Zoltan <balaton@eik.bme.hu>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
> hw/usb/host-libusb.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/hw/usb/host-libusb.c b/hw/usb/host-libusb.c
> index e28441379d99..094010d5f849 100644
> --- a/hw/usb/host-libusb.c
> +++ b/hw/usb/host-libusb.c
> @@ -951,6 +951,7 @@ fail:
> static void usb_host_abort_xfers(USBHostDevice *s)
> {
>     USBHostRequest *r, *rtmp;
> +    int limit = 100;
>
>     QTAILQ_FOREACH_SAFE(r, &s->requests, next, rtmp) {
>         usb_host_req_abort(r);
> @@ -961,6 +962,19 @@ static void usb_host_abort_xfers(USBHostDevice *s)
>         memset(&tv, 0, sizeof(tv));
>         tv.tv_usec = 2500;
>         libusb_handle_events_timeout(ctx, &tv);
> +        if (--limit == 0) {
> +            /*
> +             * Don't wait forever for libusb calling the complete
> +             * callback (which will unlink and free the request).
> +             *
> +             * Leaking memory here, to make sure libusb will not
> +             * access memory which we have released already.
> +             */
> +            QTAILQ_FOREACH_SAFE(r, &s->requests, next, rtmp) {
> +                QTAILQ_REMOVE(&s->requests, r, next);
> +            }
> +            return;
> +        }
>     }
> }