3 files changed, 51 insertions, 4 deletions

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 2fb8cb88df8d..8a6875cc1879 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -573,7 +573,8 @@ void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
                 bc->event_handler = tick_handle_oneshot_broadcast;
 
                 /* Take the do_timer update */
-                tick_do_timer_cpu = cpu;
+                if (!tick_nohz_extended_cpu(cpu))
+                        tick_do_timer_cpu = cpu;
 
                 /*
                  * We must be careful here. There might be other CPUs
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index b1600a6973f4..b7dc0cbdb59b 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -163,7 +163,10 @@ static void tick_setup_device(struct tick_device *td,
                  * this cpu:
                  */
                 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
-                        tick_do_timer_cpu = cpu;
+                        if (!tick_nohz_extended_cpu(cpu))
+                                tick_do_timer_cpu = cpu;
+                        else
+                                tick_do_timer_cpu = TICK_DO_TIMER_NONE;
                         tick_next_period = ktime_get();
                         tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
                 }
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 79c275f08b7d..57bb3fe5aaa3 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -112,7 +112,8 @@ static void tick_sched_do_timer(ktime_t now)
          * this duty, then the jiffies update is still serialized by
          * jiffies_lock.
          */
-        if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
+        if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)
+            && !tick_nohz_extended_cpu(cpu))
                 tick_do_timer_cpu = cpu;
 #endif
 
@@ -166,6 +167,25 @@ static int __init tick_nohz_extended_setup(char *str)
 }
 __setup("nohz_extended=", tick_nohz_extended_setup);
 
+static int __cpuinit tick_nohz_cpu_down_callback(struct notifier_block *nfb,
+                                                 unsigned long action,
+                                                 void *hcpu)
+{
+        unsigned int cpu = (unsigned long)hcpu;
+
+        switch (action & ~CPU_TASKS_FROZEN) {
+        case CPU_DOWN_PREPARE:
+                /*
+                 * If we handle the timekeeping duty for full dynticks CPUs,
+                 * we can't safely shutdown that CPU.
+                 */
+                if (have_nohz_extended_mask && tick_do_timer_cpu == cpu)
+                        return -EINVAL;
+                break;
+        }
+        return NOTIFY_OK;
+}
+
 static int __init init_tick_nohz_extended(void)
 {
         cpumask_var_t online_nohz;
@@ -174,6 +194,8 @@ static int __init init_tick_nohz_extended(void)
         if (!have_nohz_extended_mask)
                 return 0;
 
+        cpu_notifier(tick_nohz_cpu_down_callback, 0);
+
         if (!zalloc_cpumask_var(&online_nohz, GFP_KERNEL)) {
                 pr_warning("NO_HZ: Not enough memory to check extended nohz mask\n");
                 return -ENOMEM;
@@ -188,11 +210,17 @@ static int __init init_tick_nohz_extended(void)
         /* Ensure we keep a CPU outside the dynticks range for timekeeping */
         cpumask_and(online_nohz, cpu_online_mask, nohz_extended_mask);
         if (cpumask_equal(online_nohz, cpu_online_mask)) {
-                cpu = cpumask_any(cpu_online_mask);
                 pr_warning("NO_HZ: Must keep at least one online CPU "
                            "out of nohz_extended range\n");
+                /*
+                 * We know the current CPU doesn't have its tick stopped.
+                 * Let's use it for the timekeeping duty.
+                 */
+                preempt_disable();
+                cpu = smp_processor_id();
                 pr_warning("NO_HZ: Clearing %d from nohz_extended range\n", cpu);
                 cpumask_clear_cpu(cpu, nohz_extended_mask);
+                preempt_enable();
         }
         put_online_cpus();
         free_cpumask_var(online_nohz);
@@ -551,6 +579,21 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
                 return false;
         }
 
+        if (have_nohz_extended_mask) {
+                /*
+                 * Keep the tick alive to guarantee timekeeping progression
+                 * if there are full dynticks CPUs around
+                 */
+                if (tick_do_timer_cpu == cpu)
+                        return false;
+                /*
+                 * Boot safety: make sure the timekeeping duty has been
+                 * assigned before entering dyntick-idle mode,
+                 */
+                if (tick_do_timer_cpu == TICK_DO_TIMER_NONE)
+                        return false;
+        }
+
         return true;
 }