From 83160d14081c5b97e781e7dd9f56ffb0f4ebd5f3 Mon Sep 17 00:00:00 2001
From: Robert Watson <rwatson@FreeBSD.org>
Date: Sun, 8 Mar 2009 22:19:28 +0000
Subject: [PATCH] By default, don't compile in counters of calls to various
 time query functions in the kernel, as these effectively serialize parallel
 calls to the gettimeofday(2) system call, as well as other kernel services
 that use timestamps.

Use the NetBSD version of the fix (kern_tc.c:1.32 by ad@) as
they have picked up our timecounter code and also ran into the
same problem.

Reported by:	kris
Obtained from:	NetBSD
MFC after:	3 days
---
 sys/kern/kern_tc.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index c84054b6f5b2..640984257faf 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -103,6 +103,7 @@ static int timestepwarnings;
 SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
     &timestepwarnings, 0, "");
 
+#ifdef TC_COUNTERS
 #define TC_STATS(foo) \
 	static u_int foo; \
 	SYSCTL_UINT(_kern_timecounter, OID_AUTO, foo, CTLFLAG_RD, &foo, 0, "");\
@@ -114,7 +115,11 @@ TC_STATS(ngetbinuptime); TC_STATS(ngetnanouptime); TC_STATS(ngetmicrouptime);
 TC_STATS(ngetbintime);   TC_STATS(ngetnanotime);   TC_STATS(ngetmicrotime);
 TC_STATS(nsetclock);
 
+#define	TC_COUNT(var)	var++
 #undef TC_STATS
+#else
+#define	TC_COUNT(var)	/* nothing */
+#endif /* TC_COUNTERS */
 
 static void tc_windup(void);
 static void cpu_tick_calibrate(int);
@@ -180,7 +185,7 @@ binuptime(struct bintime *bt)
 	struct timehands *th;
 	u_int gen;
 
-	nbinuptime++;
+	TC_COUNT(nbinuptime);
 	do {
 		th = timehands;
 		gen = th->th_generation;
@@ -194,7 +199,7 @@ nanouptime(struct timespec *tsp)
 {
 	struct bintime bt;
 
-	nnanouptime++;
+	TC_COUNT(nnanouptime);
 	binuptime(&bt);
 	bintime2timespec(&bt, tsp);
 }
@@ -204,7 +209,7 @@ microuptime(struct timeval *tvp)
 {
 	struct bintime bt;
 
-	nmicrouptime++;
+	TC_COUNT(nmicrouptime);
 	binuptime(&bt);
 	bintime2timeval(&bt, tvp);
 }
@@ -213,7 +218,7 @@ void
 bintime(struct bintime *bt)
 {
 
-	nbintime++;
+	TC_COUNT(nbintime);
 	binuptime(bt);
 	bintime_add(bt, &boottimebin);
 }
@@ -223,7 +228,7 @@ nanotime(struct timespec *tsp)
 {
 	struct bintime bt;
 
-	nnanotime++;
+	TC_COUNT(nnanotime);
 	bintime(&bt);
 	bintime2timespec(&bt, tsp);
 }
@@ -233,7 +238,7 @@ microtime(struct timeval *tvp)
 {
 	struct bintime bt;
 
-	nmicrotime++;
+	TC_COUNT(nmicrotime);
 	bintime(&bt);
 	bintime2timeval(&bt, tvp);
 }
@@ -244,7 +249,7 @@ getbinuptime(struct bintime *bt)
 	struct timehands *th;
 	u_int gen;
 
-	ngetbinuptime++;
+	TC_COUNT(ngetbinuptime);
 	do {
 		th = timehands;
 		gen = th->th_generation;
@@ -258,7 +263,7 @@ getnanouptime(struct timespec *tsp)
 	struct timehands *th;
 	u_int gen;
 
-	ngetnanouptime++;
+	TC_COUNT(ngetnanouptime);
 	do {
 		th = timehands;
 		gen = th->th_generation;
@@ -272,7 +277,7 @@ getmicrouptime(struct timeval *tvp)
 	struct timehands *th;
 	u_int gen;
 
-	ngetmicrouptime++;
+	TC_COUNT(ngetmicrouptime);
 	do {
 		th = timehands;
 		gen = th->th_generation;
@@ -286,7 +291,7 @@ getbintime(struct bintime *bt)
 	struct timehands *th;
 	u_int gen;
 
-	ngetbintime++;
+	TC_COUNT(ngetbintime);
 	do {
 		th = timehands;
 		gen = th->th_generation;
@@ -301,7 +306,7 @@ getnanotime(struct timespec *tsp)
 	struct timehands *th;
 	u_int gen;
 
-	ngetnanotime++;
+	TC_COUNT(ngetnanotime);
 	do {
 		th = timehands;
 		gen = th->th_generation;
@@ -315,7 +320,7 @@ getmicrotime(struct timeval *tvp)
 	struct timehands *th;
 	u_int gen;
 
-	ngetmicrotime++;
+	TC_COUNT(ngetmicrotime);
 	do {
 		th = timehands;
 		gen = th->th_generation;
@@ -406,7 +411,7 @@ tc_setclock(struct timespec *ts)
 	struct bintime bt, bt2;
 
 	cpu_tick_calibrate(1);
-	nsetclock++;
+	TC_COUNT(nsetclock);
 	nanotime(&tbef);
 	timespec2bintime(ts, &bt);
 	binuptime(&bt2);