Hi all.
This fixes an issue I'm seeing with a uvideo(4), that doesn't like
commands we're sending to it. The camera simply sends nothing,
and since we're sleeping forever (xfer timeout is 0, which is
USBD_NO_TIMEOUT), we never get out from 'while (bulk_running)' loop,
visible in the scond chunk of the diff. This not only makes video(1)
and other V4L2 users lockup, but also results in process freeze upon
detach: it calls uvideo_vs_close(), which in turn calls
usbd_ref_wait(), which doesn't return because we still have something
in queue.
Also, in case of error we keep bulk_running set. This seems just
a leftover, as well as the first chunk: if we failed to create kthread,
there won't be anything running under bulk_running==1 for sure.
I must thank kettenis@ for help during diagnosis and mpi@ for a patch
for related issue.
OK?
--
WBR,
Vadim Zhukov
Index: uvideo.c
===================================================================
RCS file: /cvs/src/sys/dev/usb/uvideo.c,v
retrieving revision 1.205
diff -u -p -r1.205 uvideo.c
--- uvideo.c 14 Oct 2019 09:20:48 -0000 1.205
+++ uvideo.c 15 Jan 2020 21:54:43 -0000
@@ -2026,6 +2027,7 @@ uvideo_vs_start_bulk(struct uvideo_softc
error = kthread_create(uvideo_vs_start_bulk_thread, sc, NULL,
DEVNAME(sc));
if (error) {
+ sc->sc_vs_cur->bulk_running = 0;
printf("%s: can't create kernel thread!", DEVNAME(sc));
return (error);
}
@@ -2044,6 +2046,12 @@ uvideo_vs_start_bulk_thread(void *arg)
while (sc->sc_vs_cur->bulk_running) {
size = UGETDW(sc->sc_desc_probe.dwMaxPayloadTransferSize);
+ /*
+ * We can't wait infinitely, since otherwise we'll
+ * block forever if camera stops (or don't even starts)
+ * sending frames. Use '2*' multiplier to compensate
+ * possible lags.
+ */
usbd_setup_xfer(
sc->sc_vs_cur->bxfer.xfer,
sc->sc_vs_cur->pipeh,
@@ -2051,10 +2059,11 @@ uvideo_vs_start_bulk_thread(void *arg)
sc->sc_vs_cur->bxfer.buf,
size,
USBD_NO_COPY | USBD_SHORT_XFER_OK | USBD_SYNCHRONOUS,
- 0,
+ 2 * 1000 / (sc->sc_frame_rate || 1),
NULL);
error = usbd_transfer(sc->sc_vs_cur->bxfer.xfer);
if (error != USBD_NORMAL_COMPLETION) {
+ sc->sc_vs_cur->bulk_running = 0;
DPRINTF(1, "%s: error in bulk xfer: %s!\n",
DEVNAME(sc), usbd_errstr(error));
break;
