Make sysmouse(4) use its own locks, instead of using Giant.

When I changed syscons(4) to work with the MPSAFE TTY code, I just
locked all device nodes down using the compatibility feature that allows
you to override the TTY's lock (Giant in this case). Upon closer
inspection, it seems sysmouse(4) only has two internal variables that
need locking: mouse_level and mouse_status.

I haven't done any performance benchmarks on this, though I think it
won't have any dramatic improvements on the system. It is good to get
rid of Giant here, because the third argument of tty_alloc() has only
been added to ease migration to MPSAFE TTY. It should not be used when
not needed.

While there, remove SC_MOUSE, which is a leftover from the MPSAFE TTY
import.

1 files changed, 10 insertions, 14 deletions

diff --git a/sys/dev/syscons/sysmouse.c b/sys/dev/syscons/sysmouse.c
index 9d926b8..99232cb 100644
--- a/sys/dev/syscons/sysmouse.c
+++ b/sys/dev/syscons/sysmouse.c
@@ -43,8 +43,6 @@ __FBSDID("$FreeBSD$");
 
 #ifndef SC_NO_SYSMOUSE
 
-#define SC_MOUSE 	128		/* minor number */
-
 /* local variables */
 static struct tty	*sysmouse_tty;
 static int		mouse_level;	/* sysmouse protocol level */
@@ -61,7 +59,6 @@ smdev_ioctl(struct tty *tp, u_long cmd, caddr_t data, struct thread *td)
 {
 	mousehw_t *hw;
 	mousemode_t *mode;
-	int s;
 
 	switch (cmd) {
 
@@ -121,14 +118,12 @@ smdev_ioctl(struct tty *tp, u_long cmd, caddr_t data, struct thread *td)
 		return 0;
 
 	case MOUSE_GETSTATUS:	/* get accumulated mouse events */
-		s = spltty();
 		*(mousestatus_t *)data = mouse_status;
 		mouse_status.flags = 0;
 		mouse_status.obutton = mouse_status.button;
 		mouse_status.dx = 0;
 		mouse_status.dy = 0;
 		mouse_status.dz = 0;
-		splx(s);
 		return 0;
 
 #ifdef notyet
@@ -169,7 +164,7 @@ static struct ttydevsw smdev_ttydevsw = {
 static void
 sm_attach_mouse(void *unused)
 {
-	sysmouse_tty = tty_alloc(&smdev_ttydevsw, NULL, &Giant);
+	sysmouse_tty = tty_alloc(&smdev_ttydevsw, NULL, NULL);
 	tty_makedev(sysmouse_tty, NULL, "sysmouse");
 }
 
@@ -191,7 +186,9 @@ sysmouse_event(mouse_info_t *info)
 	};
 	u_char buf[8];
 	int x, y, z;
-	int i;
+	int i, flags = 0;
+
+	tty_lock(sysmouse_tty);
 
 	switch (info->operation) {
 	case MOUSE_ACTION:
@@ -210,7 +207,7 @@ sysmouse_event(mouse_info_t *info)
 			mouse_status.button &= ~info->u.event.id;
 		break;
 	default:
-		return 0;
+		goto done;
 	}
 
 	mouse_status.dx += x;
@@ -218,11 +215,9 @@ sysmouse_event(mouse_info_t *info)
 	mouse_status.dz += z;
 	mouse_status.flags |= ((x || y || z) ? MOUSE_POSCHANGED : 0)
 			      | (mouse_status.obutton ^ mouse_status.button);
-	if (mouse_status.flags == 0)
-		return 0;
-
-	if ((sysmouse_tty == NULL) || !tty_opened(sysmouse_tty))
-		return mouse_status.flags;
+	flags = mouse_status.flags;
+	if (flags == 0 || !tty_opened(sysmouse_tty))
+		goto done;
 
 	/* the first five bytes are compatible with MouseSystems' */
 	buf[0] = MOUSE_MSC_SYNC
@@ -247,7 +242,8 @@ sysmouse_event(mouse_info_t *info)
 	}
 	ttydisc_rint_done(sysmouse_tty);
 
-	return mouse_status.flags;
+done:	tty_unlock(sysmouse_tty);
+	return (flags);
 }
 
 #endif /* !SC_NO_SYSMOUSE */