Index: sys/dev/usb/ugen.c
===================================================================
RCS file: /cvsroot/src/sys/dev/usb/ugen.c,v
retrieving revision 1.134
diff -p -u -r1.134 ugen.c
--- sys/dev/usb/ugen.c	7 Jul 2016 06:55:42 -0000	1.134
+++ sys/dev/usb/ugen.c	26 Aug 2017 22:55:31 -0000
@@ -366,15 +366,12 @@ ugenopen(dev_t dev, int flag, int mode, 
 	int i, j;
 
 	sc = device_lookup_private(&ugen_cd, unit);
-	if (sc == NULL)
+	if (sc == NULL || sc->sc_dying)
 		return ENXIO;
 
 	DPRINTFN(5, ("ugenopen: flag=%d, mode=%d, unit=%d endpt=%d\n",
 		     flag, mode, unit, endpt));
 
-	if (sc == NULL || sc->sc_dying)
-		return ENXIO;
-
 	/* The control endpoint allows multiple opens. */
 	if (endpt == USB_CONTROL_ENDPOINT) {
 		sc->sc_is_open[USB_CONTROL_ENDPOINT] = 1;
@@ -513,7 +510,7 @@ ugenclose(dev_t dev, int flag, int mode,
 	int i;
 
 	sc = device_lookup_private(& ugen_cd, UGENUNIT(dev));
-	if (sc == NULL)
+	if (sc == NULL || sc->sc_dying)
 		return ENXIO;
 
 	DPRINTFN(5, ("ugenclose: flag=%d, mode=%d, unit=%d, endpt=%d\n",
@@ -589,9 +586,6 @@ ugen_do_read(struct ugen_softc *sc, int 
 
 	DPRINTFN(5, ("%s: ugenread: %d\n", device_xname(sc->sc_dev), endpt));
 
-	if (sc->sc_dying)
-		return EIO;
-
 	if (endpt == USB_CONTROL_ENDPOINT)
 		return ENODEV;
 
@@ -801,7 +795,7 @@ ugenread(dev_t dev, struct uio *uio, int
 	int error;
 
 	sc = device_lookup_private(& ugen_cd, UGENUNIT(dev));
-	if (sc == NULL)
+	if (sc == NULL || sc->sc_dying)
 		return ENXIO;
 
 	mutex_enter(&sc->sc_lock);
@@ -832,9 +826,6 @@ ugen_do_write(struct ugen_softc *sc, int
 
 	DPRINTFN(5, ("%s: ugenwrite: %d\n", device_xname(sc->sc_dev), endpt));
 
-	if (sc->sc_dying)
-		return EIO;
-
 	if (endpt == USB_CONTROL_ENDPOINT)
 		return ENODEV;
 
@@ -995,7 +986,7 @@ ugenwrite(dev_t dev, struct uio *uio, in
 	int error;
 
 	sc = device_lookup_private(& ugen_cd, UGENUNIT(dev));
-	if (sc == NULL)
+	if (sc == NULL || sc->sc_dying)
 		return ENXIO;
 
 	mutex_enter(&sc->sc_lock);
@@ -1830,7 +1821,7 @@ ugenioctl(dev_t dev, u_long cmd, void *a
 	int error;
 
 	sc = device_lookup_private(& ugen_cd, UGENUNIT(dev));
-	if (sc == NULL)
+	if (sc == NULL || sc->sc_dying)
 		return ENXIO;
 
 	sc->sc_refcnt++;
@@ -1954,6 +1945,10 @@ static int
 filt_ugenread_intr(struct knote *kn, long hint)
 {
 	struct ugen_endpoint *sce = kn->kn_hook;
+	struct ugen_softc *sc = sce->sc;
+
+	if (sc->sc_dying)
+		return 0;
 
 	kn->kn_data = sce->q.c_cc;
 	return kn->kn_data > 0;
@@ -1963,6 +1958,10 @@ static int
 filt_ugenread_isoc(struct knote *kn, long hint)
 {
 	struct ugen_endpoint *sce = kn->kn_hook;
+	struct ugen_softc *sc = sce->sc;
+
+	if (sc->sc_dying)
+		return 0;
 
 	if (sce->cur == sce->fill)
 		return 0;
@@ -1980,6 +1979,10 @@ static int
 filt_ugenread_bulk(struct knote *kn, long hint)
 {
 	struct ugen_endpoint *sce = kn->kn_hook;
+	struct ugen_softc *sc = sce->sc;
+
+	if (sc->sc_dying)
+		return 0;
 
 	if (!(sce->state & UGEN_BULK_RA))
 		/*
@@ -2001,6 +2004,10 @@ static int
 filt_ugenwrite_bulk(struct knote *kn, long hint)
 {
 	struct ugen_endpoint *sce = kn->kn_hook;
+	struct ugen_softc *sc = sce->sc;
+
+	if (sc->sc_dying)
+		return 0;
 
 	if (!(sce->state & UGEN_BULK_WB))
 		/*
@@ -2038,10 +2045,7 @@ ugenkqfilter(dev_t dev, struct knote *kn
 	struct klist *klist;
 
 	sc = device_lookup_private(&ugen_cd, UGENUNIT(dev));
-	if (sc == NULL)
-		return ENXIO;
-
-	if (sc->sc_dying)
+	if (sc == NULL || sc->sc_dying)
 		return ENXIO;
 
 	if (UGENENDPOINT(dev) == USB_CONTROL_ENDPOINT)