4 files changed, 25 insertions, 9 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index c46c931a7fe..ecfd7b5187e 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -181,12 +181,12 @@ static void clocksource_watchdog(unsigned long data)
 
 	resumed = test_and_clear_bit(0, &watchdog_resumed);
 
-	wdnow = watchdog->read();
+	wdnow = watchdog->read(watchdog);
 	wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);
 	watchdog_last = wdnow;
 
 	list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
-		csnow = cs->read();
+		csnow = cs->read(cs);
 
 		if (unlikely(resumed)) {
 			cs->wd_last = csnow;
@@ -247,7 +247,7 @@ static void clocksource_check_watchdog(struct clocksource *cs)
 
 		list_add(&cs->wd_list, &watchdog_list);
 		if (!started && watchdog) {
-			watchdog_last = watchdog->read();
+			watchdog_last = watchdog->read(watchdog);
 			watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
 			add_timer_on(&watchdog_timer,
 				     cpumask_first(cpu_online_mask));
@@ -268,7 +268,7 @@ static void clocksource_check_watchdog(struct clocksource *cs)
 				cse->flags &= ~CLOCK_SOURCE_WATCHDOG;
 			/* Start if list is not empty */
 			if (!list_empty(&watchdog_list)) {
-				watchdog_last = watchdog->read();
+				watchdog_last = watchdog->read(watchdog);
 				watchdog_timer.expires =
 					jiffies + WATCHDOG_INTERVAL;
 				add_timer_on(&watchdog_timer,
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index 06f197560f3..c3f6c30816e 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -50,7 +50,7 @@
  */
 #define JIFFIES_SHIFT	8
 
-static cycle_t jiffies_read(void)
+static cycle_t jiffies_read(struct clocksource *cs)
 {
 	return (cycle_t) jiffies;
 }
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 21a5ca84951..83c4417b6a3 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -93,7 +93,17 @@ void tick_handle_periodic(struct clock_event_device *dev)
 	for (;;) {
 		if (!clockevents_program_event(dev, next, ktime_get()))
 			return;
-		tick_periodic(cpu);
+		/*
+		 * Have to be careful here. If we're in oneshot mode,
+		 * before we call tick_periodic() in a loop, we need
+		 * to be sure we're using a real hardware clocksource.
+		 * Otherwise we could get trapped in an infinite
+		 * loop, as the tick_periodic() increments jiffies,
+		 * when then will increment time, posibly causing
+		 * the loop to trigger again and again.
+		 */
+		if (timekeeping_valid_for_hres())
+			tick_periodic(cpu);
 		next = ktime_add(next, tick_period);
 	}
 }
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 900f1b6598d..687dff49f6e 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -182,7 +182,7 @@ EXPORT_SYMBOL(do_settimeofday);
  */
 static void change_clocksource(void)
 {
-	struct clocksource *new;
+	struct clocksource *new, *old;
 
 	new = clocksource_get_next();
 
@@ -191,11 +191,16 @@ static void change_clocksource(void)
 
 	clocksource_forward_now();
 
-	new->raw_time = clock->raw_time;
+	if (clocksource_enable(new))
+		return;
 
+	new->raw_time = clock->raw_time;
+	old = clock;
 	clock = new;
+	clocksource_disable(old);
+
 	clock->cycle_last = 0;
-	clock->cycle_last = clocksource_read(new);
+	clock->cycle_last = clocksource_read(clock);
 	clock->error = 0;
 	clock->xtime_nsec = 0;
 	clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
@@ -292,6 +297,7 @@ void __init timekeeping_init(void)
 	ntp_init();
 
 	clock = clocksource_get_next();
+	clocksource_enable(clock);
 	clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
 	clock->cycle_last = clocksource_read(clock);