Protect update of the per processor switchtime variable against

interrupts.

Protect usage of the per processor switchtime variable against
interrupts in calcru().

This seem to eliminate the "microuptime() went backwards" warnings.

1 files changed, 14 insertions, 6 deletions

diff --git a/sys/kern/kern_resource.c b/sys/kern/kern_resource.c
index 73ffb03..b872acd 100644
--- a/sys/kern/kern_resource.c
+++ b/sys/kern/kern_resource.c
@@ -567,19 +567,27 @@ calcru(p, up, sp, ip)
 
 	tu = p->p_runtime;
 	if (p == curproc) {
+		struct timeval old_switchtime;
 		/*
 		 * Adjust for the current time slice.  This is actually fairly
 		 * important since the error here is on the order of a time
 		 * quantum, which is much greater than the sampling error.
 		 */
-		microuptime(&tv);
-		if (timevalcmp(&tv, PCPU_PTR(switchtime), <))
+		do {
+			old_switchtime = PCPU_GET(switchtime);
+			microuptime(&tv);
+		} while (old_switchtime.tv_sec != 
+			 PCPU_GET(switchtime.tv_sec) ||
+			 old_switchtime.tv_usec !=
+			 PCPU_GET(switchtime.tv_usec));
+		if (timevalcmp(&tv, &old_switchtime, <))
 			printf("microuptime() went backwards (%ld.%06ld -> %ld.%06ld)\n",
-			    PCPU_GET(switchtime.tv_sec), PCPU_GET(switchtime.tv_usec),
-			    tv.tv_sec, tv.tv_usec);
+			       old_switchtime.tv_sec,
+			       old_switchtime.tv_usec,
+			       tv.tv_sec, tv.tv_usec);
 		else
-			tu += (tv.tv_usec - PCPU_GET(switchtime.tv_usec)) +
-			    (tv.tv_sec - PCPU_GET(switchtime.tv_sec)) *
+			tu += (tv.tv_usec - old_switchtime.tv_usec) +
+			    (tv.tv_sec - old_switchtime.tv_sec) *
 			    (int64_t)1000000;
 	}
 	ptu = p->p_uu + p->p_su + p->p_iu;