--- sys/kern/kern_switch.c.orig	2007-06-13 04:50:31.000000000 +0900
+++ sys/kern/kern_switch.c	2007-07-18 10:21:09.000000000 +0900
@@ -192,7 +192,7 @@ critical_exit(void)
 			thread_lock(td);
 			td->td_critnest--;
 			SCHED_STAT_INC(switch_owepreempt);
-			mi_switch(SW_INVOL, NULL);
+			mi_switch(SW_INVOL|SW_PREEMPT, NULL);
 			thread_unlock(td);
 		}
 	} else