4 files changed, 25 insertions, 9 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index c46c931a7fe7..ecfd7b5187e0 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 06f197560f3b..c3f6c30816e3 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 21a5ca849514..83c4417b6a3c 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 900f1b6598d1..687dff49f6e7 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);