Index: sys/sys/callout.h
===================================================================
--- sys/sys/callout.h	(revision 243099)
+++ sys/sys/callout.h	(working copy)
@@ -96,7 +96,7 @@ int	_callout_reset_on(struct callout *, struct bin
         (0))
 #define callout_reset_flags_on(c, to_ticks, fn, arg, cpu, flags)	\
     _callout_reset_on((c), (NULL), (to_ticks), (fn), (arg), (cpu),	\
-        (flags))			
+        (flags))
 #define callout_reset_bt_on(c, bt, fn, arg, cpu, flags)			\
     _callout_reset_on((c), (bt), (0), (fn), (arg), (cpu), (flags)) 
 #define	callout_reset(c, on_tick, fn, arg)				\
Index: sys/sys/time.h
===================================================================
--- sys/sys/time.h	(revision 243099)
+++ sys/sys/time.h	(working copy)
@@ -352,7 +352,7 @@ int	tvtohz(struct timeval *tv);
             ((bt)->frac >> 1))
 
 #define	TIMESEL(x, bt)          					\
-	((x) < tc_timethreshold ? (binuptime : getbinuptime(&(bt)))
+	((x) < tc_timethreshold ? binuptime(&(bt)) : getbinuptime(&(bt)))
 
 
 #else /* !_KERNEL */
Index: sys/kern/kern_time.c
===================================================================
--- sys/kern/kern_time.c	(revision 243099)
+++ sys/kern/kern_time.c	(working copy)
@@ -483,35 +483,48 @@ int
 kern_nanosleep(struct thread *td, struct timespec *rqt, struct timespec *rmt)
 {
 	struct timespec ts;
-	struct bintime bt, bt2, tmp;
-	int error;
+	struct bintime bt, bt2, bt_prec, tmp;
+	int carry, flags, k, error;
 
 	if (rqt->tv_nsec < 0 || rqt->tv_nsec >= 1000000000)
 		return (EINVAL);
 	if (rqt->tv_sec < 0 || (rqt->tv_sec == 0 && rqt->tv_nsec == 0))
 		return (0);
-	binuptime(&bt);
+	TIMESEL(rqt->tv_nsec, bt);
 	timespec2bintime(rqt, &tmp);
-	bintime_add(&bt,&tmp);
-	for (;;) {
-		error = tsleep_bt(&nanowait, PWAIT | PCATCH, "nanslp", &bt, 0);
-		binuptime(&bt2);
-		if (error != EWOULDBLOCK) {
-			if (error == ERESTART)
-				error = EINTR;
-			if (rmt != NULL) {
-				tmp = bt;
-				bintime_sub(&tmp, &bt2);	
-				bintime2timespec(&tmp, &ts);
-				if (ts.tv_sec < 0)
-					timespecclear(&ts);
-				*rmt = ts;
-			}
-			return (error);
+	bintime_add(&bt, &tmp);
+	k = 4;
+	bt_prec = tmp;
+	bt_prec.frac >>= k;
+	carry = bt_prec.sec & ((1 << k) - 1);
+	bt_prec.sec >>= k;
+	bt_prec.frac |= (carry) ? ~(((uint64_t)1 << (64 - carry)) - 1) : 0;
+	if (rqt->tv_nsec > tc_timethreshold) {
+		bintime_add(&bt, &tick_bt);
+		if (bintime_cmp(&bt_prec, &tick_bt, <))
+			bt_prec = tick_bt;
+	}
+	flags = C_DIRECT_EXEC;
+	k = C_BT2PABS(bt_prec.frac);
+	flags |= C_SETPABS(k);
+	error = tsleep_bt(&nanowait, PWAIT | PCATCH, "nanslp", &bt, flags);
+	TIMESEL(rqt->tv_nsec, bt2);
+	if (error != EWOULDBLOCK) {
+		if (error == ERESTART)
+			error = EINTR;
+		if (rmt != NULL) {
+			tmp = bt;
+			bintime_sub(&tmp, &bt2);
+			bintime2timespec(&tmp, &ts);
+			if (ts.tv_sec < 0)
+				timespecclear(&ts);
+			*rmt = ts;
 		}
 		if (bintime_cmp(&bt2, &bt, >=))
 			return (0);
+		return (error);
 	}
+	return (0);
 }
 
 #ifndef _SYS_SYSPROTO_H_