[src/trunk]: src/sys/dev/usb In ucompoll() also bail out if we don't have a v...

[jakllsch <jakllsch%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/7ba6ec12bbfe
branches:  trunk
changeset: 772734:7ba6ec12bbfe
user:      jakllsch <jakllsch%NetBSD.org@localhost>
date:      Sat Jan 14 20:25:45 2012 +0000

description:
In ucompoll() also bail out if we don't have a valid softc.
Seems to prevent occasional crashes when a open ucom is removed.

diffstat:

 sys/dev/usb/ucom.c |  13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diffs (38 lines):

diff -r 4fda08526d2c -r 7ba6ec12bbfe sys/dev/usb/ucom.c
--- a/sys/dev/usb/ucom.c        Sat Jan 14 20:20:31 2012 +0000
+++ b/sys/dev/usb/ucom.c        Sat Jan 14 20:25:45 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ucom.c,v 1.93 2011/12/23 00:51:45 jakllsch Exp $       */
+/*     $NetBSD: ucom.c,v 1.94 2012/01/14 20:25:45 jakllsch Exp $       */
 
 /*
  * Copyright (c) 1998, 2000 The NetBSD Foundation, Inc.
@@ -34,7 +34,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ucom.c,v 1.93 2011/12/23 00:51:45 jakllsch Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ucom.c,v 1.94 2012/01/14 20:25:45 jakllsch Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -656,13 +656,16 @@
 int
 ucompoll(dev_t dev, int events, struct lwp *l)
 {
-       struct ucom_softc *sc = device_lookup_private(&ucom_cd, UCOMUNIT(dev));
-       struct tty *tp = sc->sc_tty;
+       struct ucom_softc *sc;
+       struct tty *tp;
        int revents;
 
-       if (sc->sc_dying)
+       sc = device_lookup_private(&ucom_cd, UCOMUNIT(dev));
+       if (sc == NULL || sc->sc_dying)
                return (POLLHUP);
 
+       tp = sc->sc_tty;
+
        sc->sc_refcnt++;
        revents = ((*tp->t_linesw->l_poll)(tp, events, l));
        if (--sc->sc_refcnt < 0)