viocons: BKL locking

For some weird reason I can't ascertain (translation "I think its
broken") the viocons driver calls directly into the n_tty ldisc code even
if another ldisc is in use. It'll probably break if you do that but I'm
just fixing the locking and adding a comment that its horked.
Signed-off-by: NAlan Cox <alan@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/viocons.c

@@ -704,8 +704,11 @@ static int viotty_ioctl(struct tty_struct *tty, struct file *file,
 	case KDSKBLED:
 		return 0;
 	}
-
-	return n_tty_ioctl(tty, file, cmd, arg);
+	/* FIXME: WTF is this being called for ??? */
+	lock_kernel();
+	ret =  n_tty_ioctl(tty, file, cmd, arg);
+	unlock_kernel();
+	return ret;
 }
 
 /*