2 files changed, 17 insertions, 4 deletions

diff --git a/sys/kern/kern_resource.c b/sys/kern/kern_resource.c
index fde934e96169..495175ed935b 100644
--- a/sys/kern/kern_resource.c
+++ b/sys/kern/kern_resource.c
@@ -49,6 +49,7 @@
 #include <sys/resourcevar.h>
 #include <sys/malloc.h>
 #include <sys/proc.h>
+#include <sys/time.h>
 
 #include <vm/vm.h>
 #include <vm/vm_param.h>
@@ -519,8 +520,13 @@ calcru(p, up, sp, ip)
 		 * quantum, which is much greater than the sampling error.
 		 */
 		microuptime(&tv);
-		tu += (tv.tv_usec - switchtime.tv_usec) +
-		    (tv.tv_sec - switchtime.tv_sec) * (int64_t)1000000;
+		if (timevalcmp(&tv, &switchtime, <))
+			printf("microuptime() went backwards (%ld.%06ld -> %ld,%06ld)\n",
+			    switchtime.tv_sec, switchtime.tv_usec, 
+			    tv.tv_sec, tv.tv_usec);
+		else
+			tu += (tv.tv_usec - switchtime.tv_usec) +
+			    (tv.tv_sec - switchtime.tv_sec) * (int64_t)1000000;
 	}
 	ptu = p->p_stats->p_uu + p->p_stats->p_su + p->p_stats->p_iu;
 	if (tu < ptu || (int64_t)tu < 0) {
diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index 597f5e60ffcc..16699e06bd7e 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -791,8 +791,15 @@ mi_switch()
 	 * process was running, and add that to its total so far.
 	 */
 	microuptime(&new_switchtime);
-	p->p_runtime += (new_switchtime.tv_usec - switchtime.tv_usec) +
-	    (new_switchtime.tv_sec - switchtime.tv_sec) * (int64_t)1000000;
+	if (timevalcmp(&new_switchtime, &switchtime, <)) {
+		printf("microuptime() went backwards (%ld.%06ld -> %ld,%06ld)\n",
+		    switchtime.tv_sec, switchtime.tv_usec, 
+		    new_switchtime.tv_sec, new_switchtime.tv_usec);
+		new_switchtime = switchtime;
+	} else {
+		p->p_runtime += (new_switchtime.tv_usec - switchtime.tv_usec) +
+		    (new_switchtime.tv_sec - switchtime.tv_sec) * (int64_t)1000000;
+	}
 
 	/*
 	 * Check if the process exceeds its cpu resource allocation.