1 files changed, 88 insertions, 53 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 89aed5933ed4..f992762d7f51 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -134,18 +134,13 @@ __setup("nohz=", setup_tick_nohz);
  * value. We do this unconditionally on any cpu, as we don't know whether the
  * cpu, which has the update task assigned is in a long sleep.
  */
-static void tick_nohz_update_jiffies(void)
+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;
-        ktime_t now;
-
-        if (!ts->tick_stopped)
-                return;
 
         cpumask_clear_cpu(cpu, nohz_cpu_mask);
-        now = ktime_get();
         ts->idle_waketime = now;
 
         local_irq_save(flags);
@@ -155,20 +150,17 @@ static void tick_nohz_update_jiffies(void)
         touch_softlockup_watchdog();
 }
 
-static void tick_nohz_stop_idle(int cpu)
+static void tick_nohz_stop_idle(int cpu, ktime_t now)
 {
         struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+        ktime_t delta;
 
-        if (ts->idle_active) {
-                ktime_t now, delta;
-                now = ktime_get();
-                delta = ktime_sub(now, ts->idle_entrytime);
-                ts->idle_lastupdate = now;
-                ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
-                ts->idle_active = 0;
+        delta = ktime_sub(now, ts->idle_entrytime);
+        ts->idle_lastupdate = now;
+        ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+        ts->idle_active = 0;
 
-                sched_clock_idle_wakeup_event(0);
-        }
+        sched_clock_idle_wakeup_event(0);
 }
 
 static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
@@ -216,6 +208,7 @@ void tick_nohz_stop_sched_tick(int inidle)
         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);
@@ -263,7 +256,7 @@ void tick_nohz_stop_sched_tick(int inidle)
 
                 if (ratelimit < 10) {
                         printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
-                               local_softirq_pending());
+                               (unsigned int) local_softirq_pending());
                         ratelimit++;
                 }
                 goto end;
@@ -275,14 +268,18 @@ void tick_nohz_stop_sched_tick(int inidle)
                 seq = read_seqbegin(&xtime_lock);
                 last_update = last_jiffies_update;
                 last_jiffies = jiffies;
+                time_delta = timekeeping_max_deferment();
         } while (read_seqretry(&xtime_lock, seq));
 
-        /* Get the next timer wheel timer */
-        next_jiffies = get_next_timer_interrupt(last_jiffies);
-        delta_jiffies = next_jiffies - last_jiffies;
-
-        if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu))
+        if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) ||
+            arch_needs_cpu(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;
+        }
         /*
          * Do not stop the tick, if we are only one off
          * or if the cpu is required for rcu
@@ -294,22 +291,51 @@ void tick_nohz_stop_sched_tick(int inidle)
         if ((long)delta_jiffies >= 1) {
 
                 /*
-                * calculate the expiry time for the next timer wheel
-                * timer
-                */
-                expires = ktime_add_ns(last_update, tick_period.tv64 *
-                                   delta_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.
+                 * invoked. Keep track of the fact that it was the one
+                 * which had the do_timer() duty last. If this cpu is
+                 * the one which had the do_timer() duty last, we
+                 * limit the sleep time to the timekeeping
+                 * max_deferement value which we retrieved
+                 * above. Otherwise we can sleep as long as we want.
                  */
-                if (cpu == tick_do_timer_cpu)
+                if (cpu == tick_do_timer_cpu) {
                         tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+                        ts->do_timer_last = 1;
+                } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
+                        time_delta = KTIME_MAX;
+                        ts->do_timer_last = 0;
+                } else if (!ts->do_timer_last) {
+                        time_delta = KTIME_MAX;
+                }
+
+                /*
+                 * calculate the expiry time for the next timer wheel
+                 * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals
+                 * that there is no timer pending or at least extremely
+                 * far into the future (12 days for HZ=1000). In this
+                 * case we set the expiry to the end of time.
+                 */
+                if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) {
+                        /*
+                         * Calculate the time delta for the next timer event.
+                         * If the time delta exceeds the maximum time delta
+                         * permitted by the current clocksource then adjust
+                         * the time delta accordingly to ensure the
+                         * clocksource does not wrap.
+                         */
+                        time_delta = min_t(u64, time_delta,
+                                           tick_period.tv64 * delta_jiffies);
+                }
+
+                if (time_delta < KTIME_MAX)
+                        expires = ktime_add_ns(last_update, time_delta);
+                else
+                        expires.tv64 = KTIME_MAX;
 
                 if (delta_jiffies > 1)
                         cpumask_set_cpu(cpu, nohz_cpu_mask);
@@ -342,22 +368,19 @@ void tick_nohz_stop_sched_tick(int inidle)
 
                 ts->idle_sleeps++;
 
+                /* Mark expires */
+                ts->idle_expires = expires;
+
                 /*
-                 * delta_jiffies >= NEXT_TIMER_MAX_DELTA signals that
-                 * there is no timer pending or at least extremly far
-                 * into the future (12 days for HZ=1000). In this case
-                 * we simply stop the tick timer:
+                 * If the expiration time == KTIME_MAX, then
+                 * in this case we simply stop the tick timer.
                  */
-                if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) {
-                        ts->idle_expires.tv64 = KTIME_MAX;
+                 if (unlikely(expires.tv64 == KTIME_MAX)) {
                         if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
                                 hrtimer_cancel(&ts->sched_timer);
                         goto out;
                 }
 
-                /* Mark expiries */
-                ts->idle_expires = expires;
-
                 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
                         hrtimer_start(&ts->sched_timer, expires,
                                       HRTIMER_MODE_ABS_PINNED);
@@ -436,7 +459,11 @@ void tick_nohz_restart_sched_tick(void)
         ktime_t now;
 
         local_irq_disable();
-        tick_nohz_stop_idle(cpu);
+        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;
@@ -450,7 +477,6 @@ void tick_nohz_restart_sched_tick(void)
 
         /* Update jiffies first */
         select_nohz_load_balancer(0);
-        now = ktime_get();
         tick_do_update_jiffies64(now);
         cpumask_clear_cpu(cpu, nohz_cpu_mask);
 
@@ -584,22 +610,18 @@ 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)
+static void tick_nohz_kick_tick(int cpu, 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, now;
-
-        if (!ts->tick_stopped)
-                return;
+        ktime_t delta;
 
         /*
          * Do not touch the tick device, when the next expiry is either
          * already reached or less/equal than the tick period.
          */
-        now = ktime_get();
         delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);
         if (delta.tv64 <= tick_period.tv64)
                 return;
@@ -608,9 +630,26 @@ static void tick_nohz_kick_tick(int cpu)
 #endif
 }
 
+static inline void tick_check_nohz(int cpu)
+{
+        struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+        ktime_t now;
+
+        if (!ts->idle_active && !ts->tick_stopped)
+                return;
+        now = ktime_get();
+        if (ts->idle_active)
+                tick_nohz_stop_idle(cpu, now);
+        if (ts->tick_stopped) {
+                tick_nohz_update_jiffies(now);
+                tick_nohz_kick_tick(cpu, now);
+        }
+}
+
 #else
 
 static inline void tick_nohz_switch_to_nohz(void) { }
+static inline void tick_check_nohz(int cpu) { }
 
 #endif /* NO_HZ */
 
@@ -620,11 +659,7 @@ static inline void tick_nohz_switch_to_nohz(void) { }
 void tick_check_idle(int cpu)
 {
         tick_check_oneshot_broadcast(cpu);
-#ifdef CONFIG_NO_HZ
-        tick_nohz_stop_idle(cpu);
-        tick_nohz_update_jiffies();
-        tick_nohz_kick_tick(cpu);
-#endif
+        tick_check_nohz(cpu);
 }
 
 /*