diff --git a/sys/kern/kern_timeout.c b/sys/kern/kern_timeout.c
index fb6cda32e173..831fbacaeaae 100644
--- a/sys/kern/kern_timeout.c
+++ b/sys/kern/kern_timeout.c
@@ -43,6 +43,7 @@
 #include <sys/systm.h>
 #include <sys/callout.h>
 #include <sys/kernel.h>
+#include <sys/mutex.h>
 
 /*
  * TODO:
@@ -89,6 +90,7 @@ softclock(void *dummy)
 
 	steps = 0;
 	s = splhigh();
+	mtx_enter(&sched_lock, MTX_SPIN);
 	while (softticks != ticks) {
 		softticks++;
 		/*
@@ -127,15 +129,18 @@ softclock(void *dummy)
 					c->c_flags =
 					    (c->c_flags & ~CALLOUT_PENDING);
 				}
+				mtx_exit(&sched_lock, MTX_SPIN);
 				splx(s);
 				c_func(c_arg);
 				s = splhigh();
+				mtx_enter(&sched_lock, MTX_SPIN);
 				steps = 0;
 				c = nextsoftcheck;
 			}
 		}
 	}
 	nextsoftcheck = NULL;
+	mtx_exit(&sched_lock, MTX_SPIN);
 	splx(s);
 }
 
@@ -166,6 +171,7 @@ timeout(ftn, arg, to_ticks)
 	struct callout_handle handle;
 
 	s = splhigh();
+	mtx_enter(&sched_lock, MTX_SPIN);
 
 	/* Fill in the next free callout structure. */
 	new = SLIST_FIRST(&callfree);
@@ -177,6 +183,7 @@ timeout(ftn, arg, to_ticks)
 	callout_reset(new, to_ticks, ftn, arg);
 
 	handle.callout = new;
+	mtx_exit(&sched_lock, MTX_SPIN);
 	splx(s);
 	return (handle);
 }
@@ -198,8 +205,10 @@ untimeout(ftn, arg, handle)
 		return;
 
 	s = splhigh();
+	mtx_enter(&sched_lock, MTX_SPIN);
 	if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
 		callout_stop(handle.callout);
+	mtx_exit(&sched_lock, MTX_SPIN);
 	splx(s);
 }
 
@@ -233,6 +242,7 @@ callout_reset(c, to_ticks, ftn, arg)
 	int	s;
 
 	s = splhigh();
+	mtx_enter(&sched_lock, MTX_SPIN);
 	if (c->c_flags & CALLOUT_PENDING)
 		callout_stop(c);
 
@@ -250,8 +260,8 @@ callout_reset(c, to_ticks, ftn, arg)
 	c->c_time = ticks + to_ticks;
 	TAILQ_INSERT_TAIL(&callwheel[c->c_time & callwheelmask], 
 			  c, c_links.tqe);
+	mtx_exit(&sched_lock, MTX_SPIN);
 	splx(s);
-	
 }
 
 void
@@ -261,11 +271,13 @@ callout_stop(c)
 	int	s;
 
 	s = splhigh();
+	mtx_enter(&sched_lock, MTX_SPIN);
 	/*
 	 * Don't attempt to delete a callout that's not on the queue.
 	 */
 	if (!(c->c_flags & CALLOUT_PENDING)) {
 		c->c_flags &= ~CALLOUT_ACTIVE;
+		mtx_exit(&sched_lock, MTX_SPIN);
 		splx(s);
 		return;
 	}
@@ -280,6 +292,7 @@ callout_stop(c)
 	if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
 		SLIST_INSERT_HEAD(&callfree, c, c_links.sle);
 	}
+	mtx_exit(&sched_lock, MTX_SPIN);
 	splx(s);
 }
 
@@ -341,6 +354,7 @@ adjust_timeout_calltodo(time_change)
 
 	/* don't collide with softclock() */
 	s = splhigh(); 
+	mtx_enter(&sched_lock, MTX_SPIN);
 	for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 		p->c_time -= delta_ticks;
 
@@ -351,6 +365,7 @@ adjust_timeout_calltodo(time_change)
 		/* take back the ticks the timer didn't use (p->c_time <= 0) */
 		delta_ticks = -p->c_time;
 	}
+	mtx_exit(&sched_lock, MTX_SPIN);
 	splx(s);
 
 	return;