1 files changed, 631 insertions, 248 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f992762d7f5..6558b7ac112 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -19,20 +19,25 @@
 #include <linux/percpu.h>
 #include <linux/profile.h>
 #include <linux/sched.h>
-#include <linux/tick.h>
 #include <linux/module.h>
+#include <linux/irq_work.h>
+#include <linux/posix-timers.h>
+#include <linux/perf_event.h>
+#include <linux/context_tracking.h>
 
 #include <asm/irq_regs.h>
 
 #include "tick-internal.h"
 
+#include <trace/events/timer.h>
+
 /*
  * Per cpu nohz control structure
  */
-static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
+DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
 
 /*
- * The time, when the last jiffy update happened. Protected by xtime_lock.
+ * The time, when the last jiffy update happened. Protected by jiffies_lock.
  */
 static ktime_t last_jiffies_update;
 
@@ -50,14 +55,14 @@ static void tick_do_update_jiffies64(ktime_t now)
 	ktime_t delta;
 
 	/*
-	 * Do a quick check without holding xtime_lock:
+	 * Do a quick check without holding jiffies_lock:
 	 */
 	delta = ktime_sub(now, last_jiffies_update);
 	if (delta.tv64 < tick_period.tv64)
 		return;
 
-	/* Reevalute with xtime_lock held */
-	write_seqlock(&xtime_lock);
+	/* Reevalute with jiffies_lock held */
+	write_seqlock(&jiffies_lock);
 
 	delta = ktime_sub(now, last_jiffies_update);
 	if (delta.tv64 >= tick_period.tv64) {
@@ -79,8 +84,12 @@ static void tick_do_update_jiffies64(ktime_t now)
 
 		/* Keep the tick_next_period variable up to date */
 		tick_next_period = ktime_add(last_jiffies_update, tick_period);
+	} else {
+		write_sequnlock(&jiffies_lock);
+		return;
 	}
-	write_sequnlock(&xtime_lock);
+	write_sequnlock(&jiffies_lock);
+	update_wall_time();
 }
 
 /*
@@ -90,24 +99,274 @@ static ktime_t tick_init_jiffy_update(void)
 {
 	ktime_t period;
 
-	write_seqlock(&xtime_lock);
+	write_seqlock(&jiffies_lock);
 	/* Did we start the jiffies update yet ? */
 	if (last_jiffies_update.tv64 == 0)
 		last_jiffies_update = tick_next_period;
 	period = last_jiffies_update;
-	write_sequnlock(&xtime_lock);
+	write_sequnlock(&jiffies_lock);
 	return period;
 }
 
+
+static void tick_sched_do_timer(ktime_t now)
+{
+	int cpu = smp_processor_id();
+
+#ifdef CONFIG_NO_HZ_COMMON
+	/*
+	 * 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
+	 * jiffies_lock.
+	 */
+	if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)
+	    && !tick_nohz_full_cpu(cpu))
+		tick_do_timer_cpu = cpu;
+#endif
+
+	/* Check, if the jiffies need an update */
+	if (tick_do_timer_cpu == cpu)
+		tick_do_update_jiffies64(now);
+}
+
+static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
+{
+#ifdef CONFIG_NO_HZ_COMMON
+	/*
+	 * When we are idle and the tick is stopped, we have to touch
+	 * the watchdog as we might not schedule for a really long
+	 * time. This happens on complete idle SMP systems while
+	 * waiting on the login prompt. We also increment the "start of
+	 * idle" jiffy stamp so the idle accounting adjustment we do
+	 * when we go busy again does not account too much ticks.
+	 */
+	if (ts->tick_stopped) {
+		touch_softlockup_watchdog();
+		if (is_idle_task(current))
+			ts->idle_jiffies++;
+	}
+#endif
+	update_process_times(user_mode(regs));
+	profile_tick(CPU_PROFILING);
+}
+
+#ifdef CONFIG_NO_HZ_FULL
+cpumask_var_t tick_nohz_full_mask;
+bool tick_nohz_full_running;
+
+static bool can_stop_full_tick(void)
+{
+	WARN_ON_ONCE(!irqs_disabled());
+
+	if (!sched_can_stop_tick()) {
+		trace_tick_stop(0, "more than 1 task in runqueue\n");
+		return false;
+	}
+
+	if (!posix_cpu_timers_can_stop_tick(current)) {
+		trace_tick_stop(0, "posix timers running\n");
+		return false;
+	}
+
+	if (!perf_event_can_stop_tick()) {
+		trace_tick_stop(0, "perf events running\n");
+		return false;
+	}
+
+	/* sched_clock_tick() needs us? */
+#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
+	/*
+	 * TODO: kick full dynticks CPUs when
+	 * sched_clock_stable is set.
+	 */
+	if (!sched_clock_stable()) {
+		trace_tick_stop(0, "unstable sched clock\n");
+		/*
+		 * Don't allow the user to think they can get
+		 * full NO_HZ with this machine.
+		 */
+		WARN_ONCE(tick_nohz_full_running,
+			  "NO_HZ FULL will not work with unstable sched clock");
+		return false;
+	}
+#endif
+
+	return true;
+}
+
+static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);
+
+/*
+ * Re-evaluate the need for the tick on the current CPU
+ * and restart it if necessary.
+ */
+void __tick_nohz_full_check(void)
+{
+	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
+
+	if (tick_nohz_full_cpu(smp_processor_id())) {
+		if (ts->tick_stopped && !is_idle_task(current)) {
+			if (!can_stop_full_tick())
+				tick_nohz_restart_sched_tick(ts, ktime_get());
+		}
+	}
+}
+
+static void nohz_full_kick_work_func(struct irq_work *work)
+{
+	__tick_nohz_full_check();
+}
+
+static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
+	.func = nohz_full_kick_work_func,
+};
+
+/*
+ * Kick the current CPU if it's full dynticks in order to force it to
+ * re-evaluate its dependency on the tick and restart it if necessary.
+ */
+void tick_nohz_full_kick(void)
+{
+	if (tick_nohz_full_cpu(smp_processor_id()))
+		irq_work_queue(&__get_cpu_var(nohz_full_kick_work));
+}
+
+static void nohz_full_kick_ipi(void *info)
+{
+	__tick_nohz_full_check();
+}
+
+/*
+ * Kick all full dynticks CPUs in order to force these to re-evaluate
+ * their dependency on the tick and restart it if necessary.
+ */
+void tick_nohz_full_kick_all(void)
+{
+	if (!tick_nohz_full_running)
+		return;
+
+	preempt_disable();
+	smp_call_function_many(tick_nohz_full_mask,
+			       nohz_full_kick_ipi, NULL, false);
+	tick_nohz_full_kick();
+	preempt_enable();
+}
+
+/*
+ * Re-evaluate the need for the tick as we switch the current task.
+ * It might need the tick due to per task/process properties:
+ * perf events, posix cpu timers, ...
+ */
+void __tick_nohz_task_switch(struct task_struct *tsk)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	if (!tick_nohz_full_cpu(smp_processor_id()))
+		goto out;
+
+	if (tick_nohz_tick_stopped() && !can_stop_full_tick())
+		tick_nohz_full_kick();
+
+out:
+	local_irq_restore(flags);
+}
+
+/* Parse the boot-time nohz CPU list from the kernel parameters. */
+static int __init tick_nohz_full_setup(char *str)
+{
+	int cpu;
+
+	alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
+	if (cpulist_parse(str, tick_nohz_full_mask) < 0) {
+		pr_warning("NOHZ: Incorrect nohz_full cpumask\n");
+		return 1;
+	}
+
+	cpu = smp_processor_id();
+	if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) {
+		pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu);
+		cpumask_clear_cpu(cpu, tick_nohz_full_mask);
+	}
+	tick_nohz_full_running = true;
+
+	return 1;
+}
+__setup("nohz_full=", tick_nohz_full_setup);
+
+static int 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 (tick_nohz_full_running && tick_do_timer_cpu == cpu)
+			return NOTIFY_BAD;
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+/*
+ * Worst case string length in chunks of CPU range seems 2 steps
+ * separations: 0,2,4,6,...
+ * This is NR_CPUS + sizeof('\0')
+ */
+static char __initdata nohz_full_buf[NR_CPUS + 1];
+
+static int tick_nohz_init_all(void)
+{
+	int err = -1;
+
+#ifdef CONFIG_NO_HZ_FULL_ALL
+	if (!alloc_cpumask_var(&tick_nohz_full_mask, GFP_KERNEL)) {
+		pr_err("NO_HZ: Can't allocate full dynticks cpumask\n");
+		return err;
+	}
+	err = 0;
+	cpumask_setall(tick_nohz_full_mask);
+	cpumask_clear_cpu(smp_processor_id(), tick_nohz_full_mask);
+	tick_nohz_full_running = true;
+#endif
+	return err;
+}
+
+void __init tick_nohz_init(void)
+{
+	int cpu;
+
+	if (!tick_nohz_full_running) {
+		if (tick_nohz_init_all() < 0)
+			return;
+	}
+
+	for_each_cpu(cpu, tick_nohz_full_mask)
+		context_tracking_cpu_set(cpu);
+
+	cpu_notifier(tick_nohz_cpu_down_callback, 0);
+	cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), tick_nohz_full_mask);
+	pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf);
+}
+#endif
+
 /*
  * NOHZ - aka dynamic tick functionality
  */
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
 /*
  * NO HZ enabled ?
  */
 static int tick_nohz_enabled __read_mostly  = 1;
-
+int tick_nohz_active  __read_mostly;
 /*
  * Enable / Disable tickless mode
  */
@@ -136,12 +395,9 @@ __setup("nohz=", setup_tick_nohz);
  */
 static void tick_nohz_update_jiffies(ktime_t now)
 {
-	int cpu = smp_processor_id();
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 	unsigned long flags;
 
-	cpumask_clear_cpu(cpu, nohz_cpu_mask);
-	ts->idle_waketime = now;
+	__this_cpu_write(tick_cpu_sched.idle_waketime, now);
 
 	local_irq_save(flags);
 	tick_do_update_jiffies64(now);
@@ -150,14 +406,31 @@ static void tick_nohz_update_jiffies(ktime_t now)
 	touch_softlockup_watchdog();
 }
 
-static void tick_nohz_stop_idle(int cpu, ktime_t now)
+/*
+ * Updates the per cpu time idle statistics counters
+ */
+static void
+update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time)
 {
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 	ktime_t delta;
 
-	delta = ktime_sub(now, ts->idle_entrytime);
-	ts->idle_lastupdate = now;
-	ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+	if (ts->idle_active) {
+		delta = ktime_sub(now, ts->idle_entrytime);
+		if (nr_iowait_cpu(cpu) > 0)
+			ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
+		else
+			ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+		ts->idle_entrytime = now;
+	}
+
+	if (last_update_time)
+		*last_update_time = ktime_to_us(now);
+
+}
+
+static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
+{
+	update_ts_time_stats(smp_processor_id(), ts, now, NULL);
 	ts->idle_active = 0;
 
 	sched_clock_idle_wakeup_event(0);
@@ -165,126 +438,132 @@ static void tick_nohz_stop_idle(int cpu, ktime_t now)
 
 static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
 {
-	ktime_t now, delta;
+	ktime_t now = ktime_get();
 
-	now = ktime_get();
-	if (ts->idle_active) {
-		delta = ktime_sub(now, ts->idle_entrytime);
-		ts->idle_lastupdate = now;
-		ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
-	}
 	ts->idle_entrytime = now;
 	ts->idle_active = 1;
 	sched_clock_idle_sleep_event();
 	return now;
 }
 
+/**
+ * get_cpu_idle_time_us - get the total idle time of a cpu
+ * @cpu: CPU number to query
+ * @last_update_time: variable to store update time in. Do not update
+ * counters if NULL.
+ *
+ * Return the cummulative idle time (since boot) for a given
+ * CPU, in microseconds.
+ *
+ * This time is measured via accounting rather than sampling,
+ * and is as accurate as ktime_get() is.
+ *
+ * This function returns -1 if NOHZ is not enabled.
+ */
 u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
 {
 	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+	ktime_t now, idle;
 
-	if (!tick_nohz_enabled)
+	if (!tick_nohz_active)
 		return -1;
 
-	if (ts->idle_active)
-		*last_update_time = ktime_to_us(ts->idle_lastupdate);
-	else
-		*last_update_time = ktime_to_us(ktime_get());
+	now = ktime_get();
+	if (last_update_time) {
+		update_ts_time_stats(cpu, ts, now, last_update_time);
+		idle = ts->idle_sleeptime;
+	} else {
+		if (ts->idle_active && !nr_iowait_cpu(cpu)) {
+			ktime_t delta = ktime_sub(now, ts->idle_entrytime);
+
+			idle = ktime_add(ts->idle_sleeptime, delta);
+		} else {
+			idle = ts->idle_sleeptime;
+		}
+	}
+
+	return ktime_to_us(idle);
 
-	return ktime_to_us(ts->idle_sleeptime);
 }
 EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
 
 /**
- * tick_nohz_stop_sched_tick - stop the idle tick from the idle task
+ * get_cpu_iowait_time_us - get the total iowait time of a cpu
+ * @cpu: CPU number to query
+ * @last_update_time: variable to store update time in. Do not update
+ * counters if NULL.
  *
- * When the next event is more than a tick into the future, stop the idle tick
- * Called either from the idle loop or from irq_exit() when an idle period was
- * just interrupted by an interrupt which did not cause a reschedule.
+ * Return the cummulative iowait time (since boot) for a given
+ * CPU, in microseconds.
+ *
+ * This time is measured via accounting rather than sampling,
+ * and is as accurate as ktime_get() is.
+ *
+ * This function returns -1 if NOHZ is not enabled.
  */
-void tick_nohz_stop_sched_tick(int inidle)
+u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
 {
-	unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags;
-	struct tick_sched *ts;
-	ktime_t last_update, expires, now;
-	struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
-	u64 time_delta;
-	int cpu;
-
-	local_irq_save(flags);
-
-	cpu = smp_processor_id();
-	ts = &per_cpu(tick_cpu_sched, cpu);
-
-	/*
-	 * Call to tick_nohz_start_idle stops the last_update_time from being
-	 * updated. Thus, it must not be called in the event we are called from
-	 * irq_exit() with the prior state different than idle.
-	 */
-	if (!inidle && !ts->inidle)
-		goto end;
+	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+	ktime_t now, iowait;
 
-	/*
-	 * Set ts->inidle unconditionally. Even if the system did not
-	 * switch to NOHZ mode the cpu frequency governers rely on the
-	 * update of the idle time accounting in tick_nohz_start_idle().
-	 */
-	ts->inidle = 1;
+	if (!tick_nohz_active)
+		return -1;
 
-	now = tick_nohz_start_idle(ts);
+	now = ktime_get();
+	if (last_update_time) {
+		update_ts_time_stats(cpu, ts, now, last_update_time);
+		iowait = ts->iowait_sleeptime;
+	} else {
+		if (ts->idle_active && nr_iowait_cpu(cpu) > 0) {
+			ktime_t delta = ktime_sub(now, ts->idle_entrytime);
 
-	/*
-	 * If this cpu is offline and it 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. If we don't drop
-	 * this here the jiffies might be stale and do_timer() never
-	 * invoked.
-	 */
-	if (unlikely(!cpu_online(cpu))) {
-		if (cpu == tick_do_timer_cpu)
-			tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+			iowait = ktime_add(ts->iowait_sleeptime, delta);
+		} else {
+			iowait = ts->iowait_sleeptime;
+		}
 	}
 
-	if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
-		goto end;
-
-	if (need_resched())
-		goto end;
+	return ktime_to_us(iowait);
+}
+EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
 
-	if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
-		static int ratelimit;
+static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
+					 ktime_t now, int cpu)
+{
+	unsigned long seq, last_jiffies, next_jiffies, delta_jiffies;
+	ktime_t last_update, expires, ret = { .tv64 = 0 };
+	unsigned long rcu_delta_jiffies;
+	struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
+	u64 time_delta;
 
-		if (ratelimit < 10) {
-			printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
-			       (unsigned int) local_softirq_pending());
-			ratelimit++;
-		}
-		goto end;
-	}
+	time_delta = timekeeping_max_deferment();
 
-	ts->idle_calls++;
 	/* Read jiffies and the time when jiffies were updated last */
 	do {
-		seq = read_seqbegin(&xtime_lock);
+		seq = read_seqbegin(&jiffies_lock);
 		last_update = last_jiffies_update;
 		last_jiffies = jiffies;
-		time_delta = timekeeping_max_deferment();
-	} while (read_seqretry(&xtime_lock, seq));
+	} while (read_seqretry(&jiffies_lock, seq));
 
-	if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) ||
-	    arch_needs_cpu(cpu)) {
+	if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
+	    arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
 		next_jiffies = last_jiffies + 1;
 		delta_jiffies = 1;
 	} else {
 		/* Get the next timer wheel timer */
 		next_jiffies = get_next_timer_interrupt(last_jiffies);
 		delta_jiffies = next_jiffies - last_jiffies;
+		if (rcu_delta_jiffies < delta_jiffies) {
+			next_jiffies = last_jiffies + rcu_delta_jiffies;
+			delta_jiffies = rcu_delta_jiffies;
+		}
 	}
+
 	/*
-	 * Do not stop the tick, if we are only one off
-	 * or if the cpu is required for rcu
+	 * Do not stop the tick, if we are only one off (or less)
+	 * or if the cpu is required for RCU:
 	 */
-	if (!ts->tick_stopped && delta_jiffies == 1)
+	if (!ts->tick_stopped && delta_jiffies <= 1)
 		goto out;
 
 	/* Schedule the tick, if we are at least one jiffie off */
@@ -313,6 +592,13 @@ void tick_nohz_stop_sched_tick(int inidle)
 			time_delta = KTIME_MAX;
 		}
 
+#ifdef CONFIG_NO_HZ_FULL
+		if (!ts->inidle) {
+			time_delta = min(time_delta,
+					 scheduler_tick_max_deferment());
+		}
+#endif
+
 		/*
 		 * calculate the expiry time for the next timer wheel
 		 * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals
@@ -337,13 +623,12 @@ void tick_nohz_stop_sched_tick(int inidle)
 		else
 			expires.tv64 = KTIME_MAX;
 
-		if (delta_jiffies > 1)
-			cpumask_set_cpu(cpu, nohz_cpu_mask);
-
 		/* Skip reprogram of event if its not changed */
 		if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
 			goto out;
 
+		ret = expires;
+
 		/*
 		 * nohz_stop_sched_tick can be called several times before
 		 * the nohz_restart_sched_tick is called. This happens when
@@ -352,25 +637,14 @@ void tick_nohz_stop_sched_tick(int inidle)
 		 * the scheduler tick in nohz_restart_sched_tick.
 		 */
 		if (!ts->tick_stopped) {
-			if (select_nohz_load_balancer(1)) {
-				/*
-				 * sched tick not stopped!
-				 */
-				cpumask_clear_cpu(cpu, nohz_cpu_mask);
-				goto out;
-			}
+			nohz_balance_enter_idle(cpu);
+			calc_load_enter_idle();
 
-			ts->idle_tick = hrtimer_get_expires(&ts->sched_timer);
+			ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
 			ts->tick_stopped = 1;
-			ts->idle_jiffies = last_jiffies;
-			rcu_enter_nohz();
+			trace_tick_stop(1, " ");
 		}
 
-		ts->idle_sleeps++;
-
-		/* Mark expires */
-		ts->idle_expires = expires;
-
 		/*
 		 * If the expiration time == KTIME_MAX, then
 		 * in this case we simply stop the tick timer.
@@ -395,15 +669,162 @@ void tick_nohz_stop_sched_tick(int inidle)
 		 * softirq.
 		 */
 		tick_do_update_jiffies64(ktime_get());
-		cpumask_clear_cpu(cpu, nohz_cpu_mask);
 	}
 	raise_softirq_irqoff(TIMER_SOFTIRQ);
 out:
 	ts->next_jiffies = next_jiffies;
 	ts->last_jiffies = last_jiffies;
 	ts->sleep_length = ktime_sub(dev->next_event, now);
-end:
-	local_irq_restore(flags);
+
+	return ret;
+}
+
+static void tick_nohz_full_stop_tick(struct tick_sched *ts)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	int cpu = smp_processor_id();
+
+	if (!tick_nohz_full_cpu(cpu) || is_idle_task(current))
+		return;
+
+	if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
+		return;
+
+	if (!can_stop_full_tick())
+		return;
+
+	tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
+#endif
+}
+
+static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
+{
+	/*
+	 * If this cpu is offline and it 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. If we don't drop
+	 * this here the jiffies might be stale and do_timer() never
+	 * invoked.
+	 */
+	if (unlikely(!cpu_online(cpu))) {
+		if (cpu == tick_do_timer_cpu)
+			tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+		return false;
+	}
+
+	if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) {
+		ts->sleep_length = (ktime_t) { .tv64 = NSEC_PER_SEC/HZ };
+		return false;
+	}
+
+	if (need_resched())
+		return false;
+
+	if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
+		static int ratelimit;
+
+		if (ratelimit < 10 &&
+		    (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) {
+			pr_warn("NOHZ: local_softirq_pending %02x\n",
+				(unsigned int) local_softirq_pending());
+			ratelimit++;
+		}
+		return false;
+	}
+
+	if (tick_nohz_full_enabled()) {
+		/*
+		 * 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;
+}
+
+static void __tick_nohz_idle_enter(struct tick_sched *ts)
+{
+	ktime_t now, expires;
+	int cpu = smp_processor_id();
+
+	now = tick_nohz_start_idle(ts);
+
+	if (can_stop_idle_tick(cpu, ts)) {
+		int was_stopped = ts->tick_stopped;
+
+		ts->idle_calls++;
+
+		expires = tick_nohz_stop_sched_tick(ts, now, cpu);
+		if (expires.tv64 > 0LL) {
+			ts->idle_sleeps++;
+			ts->idle_expires = expires;
+		}
+
+		if (!was_stopped && ts->tick_stopped)
+			ts->idle_jiffies = ts->last_jiffies;
+	}
+}
+
+/**
+ * tick_nohz_idle_enter - stop the idle tick from the idle task
+ *
+ * When the next event is more than a tick into the future, stop the idle tick
+ * Called when we start the idle loop.
+ *
+ * The arch is responsible of calling:
+ *
+ * - rcu_idle_enter() after its last use of RCU before the CPU is put
+ *  to sleep.
+ * - rcu_idle_exit() before the first use of RCU after the CPU is woken up.
+ */
+void tick_nohz_idle_enter(void)
+{
+	struct tick_sched *ts;
+
+	WARN_ON_ONCE(irqs_disabled());
+
+	/*
+ 	 * Update the idle state in the scheduler domain hierarchy
+ 	 * when tick_nohz_stop_sched_tick() is called from the idle loop.
+ 	 * State will be updated to busy during the first busy tick after
+ 	 * exiting idle.
+ 	 */
+	set_cpu_sd_state_idle();
+
+	local_irq_disable();
+
+	ts = &__get_cpu_var(tick_cpu_sched);
+	ts->inidle = 1;
+	__tick_nohz_idle_enter(ts);
+
+	local_irq_enable();
+}
+EXPORT_SYMBOL_GPL(tick_nohz_idle_enter);
+
+/**
+ * tick_nohz_irq_exit - update next tick event from interrupt exit
+ *
+ * When an interrupt fires while we are idle and it doesn't cause
+ * a reschedule, it may still add, modify or delete a timer, enqueue
+ * an RCU callback, etc...
+ * So we need to re-calculate and reprogram the next tick event.
+ */
+void tick_nohz_irq_exit(void)
+{
+	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
+
+	if (ts->inidle)
+		__tick_nohz_idle_enter(ts);
+	else
+		tick_nohz_full_stop_tick(ts);
 }
 
 /**
@@ -421,7 +842,7 @@ ktime_t tick_nohz_get_sleep_length(void)
 static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 {
 	hrtimer_cancel(&ts->sched_timer);
-	hrtimer_set_expires(&ts->sched_timer, ts->idle_tick);
+	hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
 
 	while (1) {
 		/* Forward the time to expire in the future */
@@ -438,49 +859,36 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 				hrtimer_get_expires(&ts->sched_timer), 0))
 				break;
 		}
-		/* Update jiffies and reread time */
-		tick_do_update_jiffies64(now);
+		/* Reread time and update jiffies */
 		now = ktime_get();
+		tick_do_update_jiffies64(now);
 	}
 }
 
-/**
- * tick_nohz_restart_sched_tick - restart the idle tick from the idle task
- *
- * Restart the idle tick when the CPU is woken up from idle
- */
-void tick_nohz_restart_sched_tick(void)
+static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
 {
-	int cpu = smp_processor_id();
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
-#ifndef CONFIG_VIRT_CPU_ACCOUNTING
-	unsigned long ticks;
-#endif
-	ktime_t now;
-
-	local_irq_disable();
-	if (ts->idle_active || (ts->inidle && ts->tick_stopped))
-		now = ktime_get();
-
-	if (ts->idle_active)
-		tick_nohz_stop_idle(cpu, now);
-
-	if (!ts->inidle || !ts->tick_stopped) {
-		ts->inidle = 0;
-		local_irq_enable();
-		return;
-	}
+	/* Update jiffies first */
+	tick_do_update_jiffies64(now);
+	update_cpu_load_nohz();
 
-	ts->inidle = 0;
+	calc_load_exit_idle();
+	touch_softlockup_watchdog();
+	/*
+	 * Cancel the scheduled timer and restore the tick
+	 */
+	ts->tick_stopped  = 0;
+	ts->idle_exittime = now;
 
-	rcu_exit_nohz();
+	tick_nohz_restart(ts, now);
+}
 
-	/* Update jiffies first */
-	select_nohz_load_balancer(0);
-	tick_do_update_jiffies64(now);
-	cpumask_clear_cpu(cpu, nohz_cpu_mask);
+static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
+{
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
+	unsigned long ticks;
 
-#ifndef CONFIG_VIRT_CPU_ACCOUNTING
+	if (vtime_accounting_enabled())
+		return;
 	/*
 	 * We stopped the tick in idle. Update process times would miss the
 	 * time we slept as update_process_times does only a 1 tick
@@ -493,18 +901,40 @@ void tick_nohz_restart_sched_tick(void)
 	if (ticks && ticks < LONG_MAX)
 		account_idle_ticks(ticks);
 #endif
+}
 
-	touch_softlockup_watchdog();
-	/*
-	 * Cancel the scheduled timer and restore the tick
-	 */
-	ts->tick_stopped  = 0;
-	ts->idle_exittime = now;
+/**
+ * tick_nohz_idle_exit - restart the idle tick from the idle task
+ *
+ * Restart the idle tick when the CPU is woken up from idle
+ * This also exit the RCU extended quiescent state. The CPU
+ * can use RCU again after this function is called.
+ */
+void tick_nohz_idle_exit(void)
+{
+	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
+	ktime_t now;
 
-	tick_nohz_restart(ts, now);
+	local_irq_disable();
+
+	WARN_ON_ONCE(!ts->inidle);
+
+	ts->inidle = 0;
+
+	if (ts->idle_active || ts->tick_stopped)
+		now = ktime_get();
+
+	if (ts->idle_active)
+		tick_nohz_stop_idle(ts, now);
+
+	if (ts->tick_stopped) {
+		tick_nohz_restart_sched_tick(ts, now);
+		tick_nohz_account_idle_ticks(ts);
+	}
 
 	local_irq_enable();
 }
+EXPORT_SYMBOL_GPL(tick_nohz_idle_exit);
 
 static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now)
 {
@@ -519,40 +949,12 @@ 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 == TICK_DO_TIMER_NONE))
-		tick_do_timer_cpu = cpu;
-
-	/* Check, if the jiffies need an update */
-	if (tick_do_timer_cpu == cpu)
-		tick_do_update_jiffies64(now);
-
-	/*
-	 * When we are idle and the tick is stopped, we have to touch
-	 * the watchdog as we might not schedule for a really long
-	 * time. This happens on complete idle SMP systems while
-	 * waiting on the login prompt. We also increment the "start
-	 * of idle" jiffy stamp so the idle accounting adjustment we
-	 * do when we go busy again does not account too much ticks.
-	 */
-	if (ts->tick_stopped) {
-		touch_softlockup_watchdog();
-		ts->idle_jiffies++;
-	}
-
-	update_process_times(user_mode(regs));
-	profile_tick(CPU_PROFILING);
+	tick_sched_do_timer(now);
+	tick_sched_handle(ts, regs);
 
 	while (tick_nohz_reprogram(ts, now)) {
 		now = ktime_get();
@@ -576,7 +978,7 @@ static void tick_nohz_switch_to_nohz(void)
 		local_irq_enable();
 		return;
 	}
-
+	tick_nohz_active = 1;
 	ts->nohz_mode = NOHZ_MODE_LOWRES;
 
 	/*
@@ -594,9 +996,6 @@ static void tick_nohz_switch_to_nohz(void)
 		next = ktime_add(next, tick_period);
 	}
 	local_irq_enable();
-
-	printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n",
-	       smp_processor_id());
 }
 
 /*
@@ -610,12 +1009,10 @@ static void tick_nohz_switch_to_nohz(void)
  * timer and do not touch the other magic bits which need to be done
  * when idle is left.
  */
-static void tick_nohz_kick_tick(int cpu, ktime_t now)
+static void tick_nohz_kick_tick(struct tick_sched *ts, ktime_t now)
 {
 #if 0
 	/* Switch back to 2.6.27 behaviour */
-
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 	ktime_t delta;
 
 	/*
@@ -630,36 +1027,36 @@ static void tick_nohz_kick_tick(int cpu, ktime_t now)
 #endif
 }
 
-static inline void tick_check_nohz(int cpu)
+static inline void tick_nohz_irq_enter(void)
 {
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
 	ktime_t now;
 
 	if (!ts->idle_active && !ts->tick_stopped)
 		return;
 	now = ktime_get();
 	if (ts->idle_active)
-		tick_nohz_stop_idle(cpu, now);
+		tick_nohz_stop_idle(ts, now);
 	if (ts->tick_stopped) {
 		tick_nohz_update_jiffies(now);
-		tick_nohz_kick_tick(cpu, now);
+		tick_nohz_kick_tick(ts, now);
 	}
 }
 
 #else
 
 static inline void tick_nohz_switch_to_nohz(void) { }
-static inline void tick_check_nohz(int cpu) { }
+static inline void tick_nohz_irq_enter(void) { }
 
-#endif /* NO_HZ */
+#endif /* CONFIG_NO_HZ_COMMON */
 
 /*
  * Called from irq_enter to notify about the possible interruption of idle()
  */
-void tick_check_idle(int cpu)
+void tick_irq_enter(void)
 {
-	tick_check_oneshot_broadcast(cpu);
-	tick_check_nohz(cpu);
+	tick_check_oneshot_broadcast_this_cpu();
+	tick_nohz_irq_enter();
 }
 
 /*
@@ -668,7 +1065,7 @@ void tick_check_idle(int cpu)
 #ifdef CONFIG_HIGH_RES_TIMERS
 /*
  * We rearm the timer until we get disabled by the idle code.
- * Called with interrupts disabled and timer->base->cpu_base->lock held.
+ * Called with interrupts disabled.
  */
 static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
 {
@@ -676,50 +1073,31 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
 		container_of(timer, struct tick_sched, sched_timer);
 	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 == TICK_DO_TIMER_NONE))
-		tick_do_timer_cpu = cpu;
-#endif
-
-	/* Check, if the jiffies need an update */
-	if (tick_do_timer_cpu == cpu)
-		tick_do_update_jiffies64(now);
+	tick_sched_do_timer(now);
 
 	/*
 	 * Do not call, when we are not in irq context and have
 	 * no valid regs pointer
 	 */
-	if (regs) {
-		/*
-		 * When we are idle and the tick is stopped, we have to touch
-		 * the watchdog as we might not schedule for a really long
-		 * time. This happens on complete idle SMP systems while
-		 * waiting on the login prompt. We also increment the "start of
-		 * idle" jiffy stamp so the idle accounting adjustment we do
-		 * when we go busy again does not account too much ticks.
-		 */
-		if (ts->tick_stopped) {
-			touch_softlockup_watchdog();
-			ts->idle_jiffies++;
-		}
-		update_process_times(user_mode(regs));
-		profile_tick(CPU_PROFILING);
-	}
+	if (regs)
+		tick_sched_handle(ts, regs);
 
 	hrtimer_forward(timer, now, tick_period);
 
 	return HRTIMER_RESTART;
 }
 
+static int sched_skew_tick;
+
+static int __init skew_tick(char *str)
+{
+	get_option(&str, &sched_skew_tick);
+
+	return 0;
+}
+early_param("skew_tick", skew_tick);
+
 /**
  * tick_setup_sched_timer - setup the tick emulation timer
  */
@@ -727,7 +1105,6 @@ void tick_setup_sched_timer(void)
 {
 	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
 	ktime_t now = ktime_get();
-	u64 offset;
 
 	/*
 	 * Emulate tick processing via per-CPU hrtimers:
@@ -737,10 +1114,14 @@ void tick_setup_sched_timer(void)
 
 	/* Get the next period (per cpu) */
 	hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
-	offset = ktime_to_ns(tick_period) >> 1;
-	do_div(offset, num_possible_cpus());
-	offset *= smp_processor_id();
-	hrtimer_add_expires_ns(&ts->sched_timer, offset);
+
+	/* Offset the tick to avert jiffies_lock contention. */
+	if (sched_skew_tick) {
+		u64 offset = ktime_to_ns(tick_period) >> 1;
+		do_div(offset, num_possible_cpus());
+		offset *= smp_processor_id();
+		hrtimer_add_expires_ns(&ts->sched_timer, offset);
+	}
 
 	for (;;) {
 		hrtimer_forward(&ts->sched_timer, now, tick_period);
@@ -752,14 +1133,16 @@ void tick_setup_sched_timer(void)
 		now = ktime_get();
 	}
 
-#ifdef CONFIG_NO_HZ
-	if (tick_nohz_enabled)
+#ifdef CONFIG_NO_HZ_COMMON
+	if (tick_nohz_enabled) {
 		ts->nohz_mode = NOHZ_MODE_HIGHRES;
+		tick_nohz_active = 1;
+	}
 #endif
 }
 #endif /* HIGH_RES_TIMERS */
 
-#if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS
+#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
 void tick_cancel_sched_timer(int cpu)
 {
 	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
@@ -769,7 +1152,7 @@ void tick_cancel_sched_timer(int cpu)
 		hrtimer_cancel(&ts->sched_timer);
 # endif
 
-	ts->nohz_mode = NOHZ_MODE_INACTIVE;
+	memset(ts, 0, sizeof(*ts));
 }
 #endif