1 files changed, 42 insertions, 15 deletions

diff --git a/kernel/timer.c b/kernel/timer.c
index d78de047599b..87bd529879c2 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -81,6 +81,7 @@ struct tvec_base {
         unsigned long timer_jiffies;
         unsigned long next_timer;
         unsigned long active_timers;
+        unsigned long all_timers;
         struct tvec_root tv1;
         struct tvec tv2;
         struct tvec tv3;
@@ -337,6 +338,20 @@ void set_timer_slack(struct timer_list *timer, int slack_hz)
 }
 EXPORT_SYMBOL_GPL(set_timer_slack);
 
+/*
+ * If the list is empty, catch up ->timer_jiffies to the current time.
+ * The caller must hold the tvec_base lock.  Returns true if the list
+ * was empty and therefore ->timer_jiffies was updated.
+ */
+static bool catchup_timer_jiffies(struct tvec_base *base)
+{
+        if (!base->all_timers) {
+                base->timer_jiffies = jiffies;
+                return true;
+        }
+        return false;
+}
+
 static void
 __internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 {
@@ -383,15 +398,17 @@ __internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 
 static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 {
+        (void)catchup_timer_jiffies(base);
         __internal_add_timer(base, timer);
         /*
          * Update base->active_timers and base->next_timer
          */
         if (!tbase_get_deferrable(timer->base)) {
-                if (time_before(timer->expires, base->next_timer))
+                if (!base->active_timers++ ||
+                    time_before(timer->expires, base->next_timer))
                         base->next_timer = timer->expires;
-                base->active_timers++;
         }
+        base->all_timers++;
 }
 
 #ifdef CONFIG_TIMER_STATS
@@ -671,6 +688,8 @@ detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
         detach_timer(timer, true);
         if (!tbase_get_deferrable(timer->base))
                 base->active_timers--;
+        base->all_timers--;
+        (void)catchup_timer_jiffies(base);
 }
 
 static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
@@ -685,6 +704,8 @@ static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
                 if (timer->expires == base->next_timer)
                         base->next_timer = base->timer_jiffies;
         }
+        base->all_timers--;
+        (void)catchup_timer_jiffies(base);
         return 1;
 }
 
@@ -739,12 +760,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
 
         debug_activate(timer, expires);
 
-        cpu = smp_processor_id();
-
-#if defined(CONFIG_NO_HZ_COMMON) && defined(CONFIG_SMP)
-        if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
-                cpu = get_nohz_timer_target();
-#endif
+        cpu = get_nohz_timer_target(pinned);
         new_base = per_cpu(tvec_bases, cpu);
 
         if (base != new_base) {
@@ -939,8 +955,15 @@ void add_timer_on(struct timer_list *timer, int cpu)
          * with the timer by holding the timer base lock. This also
          * makes sure that a CPU on the way to stop its tick can not
          * evaluate the timer wheel.
+         *
+         * Spare the IPI for deferrable timers on idle targets though.
+         * The next busy ticks will take care of it. Except full dynticks
+         * require special care against races with idle_cpu(), lets deal
+         * with that later.
          */
-        wake_up_nohz_cpu(cpu);
+        if (!tbase_get_deferrable(timer->base) || tick_nohz_full_cpu(cpu))
+                wake_up_nohz_cpu(cpu);
+
         spin_unlock_irqrestore(&base->lock, flags);
 }
 EXPORT_SYMBOL_GPL(add_timer_on);
@@ -1146,6 +1169,10 @@ static inline void __run_timers(struct tvec_base *base)
         struct timer_list *timer;
 
         spin_lock_irq(&base->lock);
+        if (catchup_timer_jiffies(base)) {
+                spin_unlock_irq(&base->lock);
+                return;
+        }
         while (time_after_eq(jiffies, base->timer_jiffies)) {
                 struct list_head work_list;
                 struct list_head *head = &work_list;
@@ -1160,7 +1187,7 @@ static inline void __run_timers(struct tvec_base *base)
                                         !cascade(base, &base->tv4, INDEX(2)))
                         cascade(base, &base->tv5, INDEX(3));
                 ++base->timer_jiffies;
-                list_replace_init(base->tv1.vec + index, &work_list);
+                list_replace_init(base->tv1.vec + index, head);
                 while (!list_empty(head)) {
                         void (*fn)(unsigned long);
                         unsigned long data;
@@ -1523,9 +1550,8 @@ static int init_timers_cpu(int cpu)
                         if (!base)
                                 return -ENOMEM;
 
-                        /* Make sure that tvec_base is 2 byte aligned */
-                        if (tbase_get_deferrable(base)) {
-                                WARN_ON(1);
+                        /* Make sure tvec_base has TIMER_FLAG_MASK bits free */
+                        if (WARN_ON(base != tbase_get_base(base))) {
                                 kfree(base);
                                 return -ENOMEM;
                         }
@@ -1559,6 +1585,7 @@ static int init_timers_cpu(int cpu)
         base->timer_jiffies = jiffies;
         base->next_timer = base->timer_jiffies;
         base->active_timers = 0;
+        base->all_timers = 0;
         return 0;
 }
 
@@ -1648,9 +1675,9 @@ void __init init_timers(void)
 
         err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
                                (void *)(long)smp_processor_id());
-        init_timer_stats();
-
         BUG_ON(err != NOTIFY_OK);
+
+        init_timer_stats();
         register_cpu_notifier(&timers_nb);
         open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
 }