1 files changed, 40 insertions, 2 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 51556b95f60f..f4fc867f467d 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -221,6 +221,18 @@ void tick_nohz_stop_sched_tick(void)
                         ts->tick_stopped = 1;
                         ts->idle_jiffies = last_jiffies;
                 }
+
+                /*
+                 * If this cpu is the one which updates jiffies, then
+                 * give up the assignment and let it be taken by the
+                 * cpu which runs the tick timer next, which might be
+                 * this cpu as well. If we don't drop this here the
+                 * jiffies might be stale and do_timer() never
+                 * invoked.
+                 */
+                if (cpu == tick_do_timer_cpu)
+                        tick_do_timer_cpu = -1;
+
                 /*
                  * calculate the expiry time for the next timer wheel
                  * timer
@@ -338,12 +350,24 @@ static void tick_nohz_handler(struct clock_event_device *dev)
 {
         struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
         struct pt_regs *regs = get_irq_regs();
+        int cpu = smp_processor_id();
         ktime_t now = ktime_get();
 
         dev->next_event.tv64 = KTIME_MAX;
 
+        /*
+         * Check if the do_timer duty was dropped. We don't care about
+         * concurrency: This happens only when the cpu in charge went
+         * into a long sleep. If two cpus happen to assign themself to
+         * this duty, then the jiffies update is still serialized by
+         * xtime_lock.
+         */
+        if (unlikely(tick_do_timer_cpu == -1))
+                tick_do_timer_cpu = cpu;
+
         /* Check, if the jiffies need an update */
-        tick_do_update_jiffies64(now);
+        if (tick_do_timer_cpu == cpu)
+                tick_do_update_jiffies64(now);
 
         /*
          * When we are idle and the tick is stopped, we have to touch
@@ -431,9 +455,23 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
         struct hrtimer_cpu_base *base = timer->base->cpu_base;
         struct pt_regs *regs = get_irq_regs();
         ktime_t now = ktime_get();
+        int cpu = smp_processor_id();
+
+#ifdef CONFIG_NO_HZ
+        /*
+         * Check if the do_timer duty was dropped. We don't care about
+         * concurrency: This happens only when the cpu in charge went
+         * into a long sleep. If two cpus happen to assign themself to
+         * this duty, then the jiffies update is still serialized by
+         * xtime_lock.
+         */
+        if (unlikely(tick_do_timer_cpu == -1))
+                tick_do_timer_cpu = cpu;
+#endif
 
         /* Check, if the jiffies need an update */
-        tick_do_update_jiffies64(now);
+        if (tick_do_timer_cpu == cpu)
+                tick_do_update_jiffies64(now);
 
         /*
          * Do not call, when we are not in irq context and have