Index: sys/dev/led/led.c
===================================================================
--- sys/dev/led/led.c
+++ sys/dev/led/led.c
@@ -14,14 +14,17 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/ck.h>
 #include <sys/conf.h>
 #include <sys/ctype.h>
+#include <sys/epoch.h>
 #include <sys/kernel.h>
 #include <sys/limits.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/mutex.h>
 #include <sys/queue.h>
+#include <sys/refcount.h>
 #include <sys/sbuf.h>
 #include <sys/sx.h>
 #include <sys/systm.h>
@@ -30,7 +33,7 @@
 #include <dev/led/led.h>
 
 struct ledsc {
-	LIST_ENTRY(ledsc)	list;
+	CK_LIST_ENTRY(ledsc)	list;
 	char			*name;
 	void			*private;
 	int			unit;
@@ -44,11 +47,11 @@
 };
 
 static struct unrhdr *led_unit;
-static struct mtx led_mtx;
+static __read_mostly epoch_t led_epoch;
 static struct sx led_sx;
-static LIST_HEAD(, ledsc) led_list = LIST_HEAD_INITIALIZER(led_list);
+static CK_LIST_HEAD(, ledsc) led_list = CK_LIST_HEAD_INITIALIZER(led_list);
 static struct callout led_ch;
-static int blinkers = 0;
+static unsigned int blinkers;
 
 static MALLOC_DEFINE(M_LED, "LED", "LED driver");
 
@@ -56,8 +59,11 @@
 led_timeout(void *p)
 {
 	struct ledsc	*sc;
+	struct epoch_tracker et;
+	unsigned int b;
 
-	LIST_FOREACH(sc, &led_list, list) {
+	epoch_enter_preempt(led_epoch, &et);
+	CK_LIST_FOREACH(sc, &led_list, list) {
 		if (sc->ptr == NULL)
 			continue;
 		if (sc->count > 0) {
@@ -66,7 +72,7 @@
 		}
 		if (*sc->ptr == '.') {
 			sc->ptr = NULL;
-			blinkers--;
+			refcount_release(&blinkers);
 			continue;
 		} else if (*sc->ptr == 'U' || *sc->ptr == 'u') {
 			if (sc->last_second == time_second)
@@ -84,8 +90,10 @@
 		if (*sc->ptr == '\0')
 			sc->ptr = sc->str;
 	}
-	if (blinkers > 0)
+	b = refcount_load(&blinkers);
+	if (b > 0)
 		callout_reset(&led_ch, hz / 10, led_timeout, p);
+	epoch_exit_preempt(led_epoch, &et);
 }
 
 static int
@@ -98,14 +106,14 @@
 	if (*sb != NULL) {
 		sc->str = sbuf_data(*sb);
 		if (sc->ptr == NULL) {
-			blinkers++;
+			refcount_acquire(&blinkers);
 			callout_reset(&led_ch, hz / 10, led_timeout, NULL);
 		}
 		sc->ptr = sc->str;
 	} else {
 		sc->str = NULL;
 		if (sc->ptr != NULL)
-			blinkers--;
+			refcount_release(&blinkers);
 		sc->ptr = NULL;
 		sc->func(sc->private, state);
 	}
@@ -215,6 +223,7 @@
 led_write(struct cdev *dev, struct uio *uio, int ioflag)
 {
 	struct ledsc	*sc;
+	struct epoch_tracker et;
 	char *s;
 	struct sbuf *sb = NULL;
 	int error, state = 0;
@@ -232,11 +241,11 @@
 	free(s, M_DEVBUF);
 	if (error)
 		return (error);
-	mtx_lock(&led_mtx);
+	epoch_enter_preempt(led_epoch, &et);
 	sc = dev->si_drv1;
 	if (sc != NULL)
 		error = led_state(sc, &sb, state);
-	mtx_unlock(&led_mtx);
+	epoch_exit_preempt(led_epoch, &et);
 	if (sb != NULL)
 		sbuf_delete(sb);
 	return (error);
@@ -246,14 +255,16 @@
 led_set(char const *name, char const *cmd)
 {
 	struct ledsc	*sc;
+	struct epoch_tracker et;
 	struct sbuf *sb = NULL;
 	int error, state = 0;
 
 	error = led_parse(cmd, &sb, &state);
 	if (error)
 		return (error);
-	mtx_lock(&led_mtx);
-	LIST_FOREACH(sc, &led_list, list) {
+
+	epoch_enter_preempt(led_epoch, &et);
+	CK_LIST_FOREACH(sc, &led_list, list) {
 		if (strcmp(sc->name, name) == 0)
 			break;
 	}
@@ -261,7 +272,7 @@
 		error = led_state(sc, &sb, state);
 	else
 		error = ENOENT;
-	mtx_unlock(&led_mtx);
+	epoch_exit_preempt(led_epoch, &et);
 	if (sb != NULL)
 		sbuf_delete(sb);
 	return (error);
@@ -283,24 +294,25 @@
 led_create_state(led_t *func, void *priv, char const *name, int state)
 {
 	struct ledsc	*sc;
+	struct epoch_tracker et;
 
 	sc = malloc(sizeof *sc, M_LED, M_WAITOK | M_ZERO);
 
-	sx_xlock(&led_sx);
 	sc->name = strdup(name, M_LED);
 	sc->unit = alloc_unr(led_unit);
 	sc->private = priv;
 	sc->func = func;
 	sc->dev = make_dev(&led_cdevsw, sc->unit,
 	    UID_ROOT, GID_WHEEL, 0600, "led/%s", name);
-	sx_xunlock(&led_sx);
-
-	mtx_lock(&led_mtx);
 	sc->dev->si_drv1 = sc;
-	LIST_INSERT_HEAD(&led_list, sc, list);
+
+	sx_xlock(&led_sx);
+	epoch_enter_preempt(led_epoch, &et);
+	CK_LIST_INSERT_HEAD(&led_list, sc, list);
 	if (state != -1)
 		sc->func(sc->private, state != 0);
-	mtx_unlock(&led_mtx);
+	epoch_exit_preempt(led_epoch, &et);
+	sx_unlock(&led_sx);
 
 	return (sc->dev);
 }
@@ -310,17 +322,16 @@
 {
 	struct ledsc *sc;
 
-	mtx_lock(&led_mtx);
+	sx_xlock(&led_sx);
+	epoch_wait_preempt(led_epoch);
 	sc = dev->si_drv1;
 	dev->si_drv1 = NULL;
 	if (sc->ptr != NULL)
-		blinkers--;
-	LIST_REMOVE(sc, list);
-	if (LIST_EMPTY(&led_list))
+		refcount_release(&blinkers);
+	CK_LIST_REMOVE(sc, list);
+	if (CK_LIST_EMPTY(&led_list))
 		callout_stop(&led_ch);
-	mtx_unlock(&led_mtx);
 
-	sx_xlock(&led_sx);
 	free_unr(led_unit, sc->unit);
 	destroy_dev(dev);
 	if (sc->spec != NULL)
@@ -335,9 +346,10 @@
 {
 
 	led_unit = new_unrhdr(0, INT_MAX, NULL);
-	mtx_init(&led_mtx, "LED mtx", NULL, MTX_DEF);
+	led_epoch = epoch_alloc("LEDs", EPOCH_PREEMPT);
+	refcount_init(&blinkers, 0);
 	sx_init(&led_sx, "LED sx");
-	callout_init_mtx(&led_ch, &led_mtx, 0);
+	callout_init(&led_ch, 1);
 }
 
 SYSINIT(leddev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, led_drvinit, NULL);