Index: sys/dev/led/led.c
===================================================================
--- sys/dev/led/led.c
+++ sys/dev/led/led.c
@@ -17,6 +17,7 @@
 #include <sys/conf.h>
 #include <sys/ctype.h>
 #include <sys/kernel.h>
+#include <sys/kthread.h>
 #include <sys/limits.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
@@ -41,21 +42,23 @@
 	char			*ptr;
 	int			count;
 	time_t			last_second;
+	bool			in_use;
+	bool			destroying;
 };
 
 static struct unrhdr *led_unit;
 static struct mtx led_mtx;
 static struct sx led_sx;
 static LIST_HEAD(, ledsc) led_list = LIST_HEAD_INITIALIZER(led_list);
-static struct callout led_ch;
 static int blinkers = 0;
 
 static MALLOC_DEFINE(M_LED, "LED", "LED driver");
 
 static void
-led_timeout(void *p)
+led_timeout(void)
 {
 	struct ledsc	*sc;
+	int		state;
 
 	LIST_FOREACH(sc, &led_list, list) {
 		if (sc->ptr == NULL)
@@ -72,20 +75,42 @@
 			if (sc->last_second == time_second)
 				continue;
 			sc->last_second = time_second;
-			sc->func(sc->private, *sc->ptr == 'U');
+			state = *sc->ptr == 'U';
 		} else if (*sc->ptr >= 'a' && *sc->ptr <= 'j') {
-			sc->func(sc->private, 0);
+			state = 0;
 			sc->count = (*sc->ptr & 0xf) - 1;
 		} else if (*sc->ptr >= 'A' && *sc->ptr <= 'J') {
-			sc->func(sc->private, 1);
+			state = 1;
 			sc->count = (*sc->ptr & 0xf) - 1;
 		}
 		sc->ptr++;
 		if (*sc->ptr == '\0')
 			sc->ptr = sc->str;
+		sc->in_use = true;
+		mtx_unlock(&led_mtx);
+		sc->func(sc->private, state);
+		mtx_lock(&led_mtx);
+		sc->in_use = false;
+		if (sc->destroying)
+			wakeup(sc);
 	}
-	if (blinkers > 0)
-		callout_reset(&led_ch, hz / 10, led_timeout, p);
+}
+
+static void
+led_blinker_thread(void *arg __unused)
+{
+	int timeout;
+
+	mtx_lock(&led_mtx);
+	for (;;) {
+		if (blinkers > 0)
+			timeout = hz / 10;
+		else
+			timeout = 0;
+		(void)mtx_sleep(&led_list, &led_mtx, 0, "blnkwt", timeout);
+		led_timeout();
+	}
+	mtx_unlock(&led_mtx);
 }
 
 static int
@@ -95,11 +120,13 @@
 
 	sb2 = sc->spec;
 	sc->spec = *sb;
+	sc->count = 0;
 	if (*sb != NULL) {
 		sc->str = sbuf_data(*sb);
 		if (sc->ptr == NULL) {
 			blinkers++;
-			callout_reset(&led_ch, hz / 10, led_timeout, NULL);
+			if (blinkers == 1)
+				wakeup(&led_list);
 		}
 		sc->ptr = sc->str;
 	} else {
@@ -107,9 +134,12 @@
 		if (sc->ptr != NULL)
 			blinkers--;
 		sc->ptr = NULL;
+		sc->in_use = true;
+		mtx_unlock(&led_mtx);
 		sc->func(sc->private, state);
+		mtx_lock(&led_mtx);
+		sc->in_use = false;
 	}
-	sc->count = 0;
 	*sb = sb2;
 	return(0);
 }
@@ -298,9 +328,9 @@
 	mtx_lock(&led_mtx);
 	sc->dev->si_drv1 = sc;
 	LIST_INSERT_HEAD(&led_list, sc, list);
+	mtx_unlock(&led_mtx);
 	if (state != -1)
 		sc->func(sc->private, state != 0);
-	mtx_unlock(&led_mtx);
 
 	return (sc->dev);
 }
@@ -312,12 +342,13 @@
 
 	mtx_lock(&led_mtx);
 	sc = dev->si_drv1;
+	sc->destroying = true;
+	while (sc->in_use)
+		(void)mtx_sleep(sc, &led_mtx, 0, "ledbsy", 0);
 	dev->si_drv1 = NULL;
 	if (sc->ptr != NULL)
 		blinkers--;
 	LIST_REMOVE(sc, list);
-	if (LIST_EMPTY(&led_list))
-		callout_stop(&led_ch);
 	mtx_unlock(&led_mtx);
 
 	sx_xlock(&led_sx);
@@ -337,7 +368,11 @@
 	led_unit = new_unrhdr(0, INT_MAX, NULL);
 	mtx_init(&led_mtx, "LED mtx", NULL, MTX_DEF);
 	sx_init(&led_sx, "LED sx");
-	callout_init_mtx(&led_ch, &led_mtx, 0);
+
+	if (kproc_create(led_blinker_thread, NULL, NULL, 0, 0,
+	    "led blinker") != 0) {
+		panic("led_drvinit: can't create thread");
+	}
 }
 
 SYSINIT(leddev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, led_drvinit, NULL);