hrtimer: fixup the HRTIMER_CB_IRQSAFE_NO_SOFTIRQ fallback

Currently all highres=off timers are run from softirq context, but
HRTIMER_CB_IRQSAFE_NO_SOFTIRQ timers expect to run from irq context.

Fix this up by splitting it similar to the highres=on case.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 143 insertions, 135 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index ecc8e2685e2b..49067f14fac1 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -115,10 +115,8 @@ struct hrtimer {
         enum hrtimer_restart            (*function)(struct hrtimer *);
         struct hrtimer_clock_base       *base;
         unsigned long                   state;
-#ifdef CONFIG_HIGH_RES_TIMERS
         enum hrtimer_cb_mode            cb_mode;
         struct list_head                cb_entry;
-#endif
 #ifdef CONFIG_TIMER_STATS
         void                            *start_site;
         char                            start_comm[16];
@@ -194,10 +192,10 @@ struct hrtimer_cpu_base {
         spinlock_t                      lock;
         struct lock_class_key           lock_key;
         struct hrtimer_clock_base       clock_base[HRTIMER_MAX_CLOCK_BASES];
+        struct list_head                cb_pending;
 #ifdef CONFIG_HIGH_RES_TIMERS
         ktime_t                         expires_next;
         int                             hres_active;
-        struct list_head                cb_pending;
         unsigned long                   nr_events;
 #endif
 };
@@ -319,6 +317,7 @@ extern void hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
 
 /* Soft interrupt function to run the hrtimer queues: */
 extern void hrtimer_run_queues(void);
+extern void hrtimer_run_pending(void);
 
 /* Bootup initialization: */
 extern void __init hrtimers_init(void);
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 9f850ca032b6..061ae28a36a0 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -325,6 +325,22 @@ unsigned long ktime_divns(const ktime_t kt, s64 div)
 }
 #endif /* BITS_PER_LONG >= 64 */
 
+/*
+ * Check, whether the timer is on the callback pending list
+ */
+static inline int hrtimer_cb_pending(const struct hrtimer *timer)
+{
+        return timer->state & HRTIMER_STATE_PENDING;
+}
+
+/*
+ * Remove a timer from the callback pending list
+ */
+static inline void hrtimer_remove_cb_pending(struct hrtimer *timer)
+{
+        list_del_init(&timer->cb_entry);
+}
+
 /* High resolution timer related functions */
 #ifdef CONFIG_HIGH_RES_TIMERS
 
@@ -494,29 +510,12 @@ void hres_timers_resume(void)
 }
 
 /*
- * Check, whether the timer is on the callback pending list
- */
-static inline int hrtimer_cb_pending(const struct hrtimer *timer)
-{
-        return timer->state & HRTIMER_STATE_PENDING;
-}
-
-/*
- * Remove a timer from the callback pending list
- */
-static inline void hrtimer_remove_cb_pending(struct hrtimer *timer)
-{
-        list_del_init(&timer->cb_entry);
-}
-
-/*
  * Initialize the high resolution related parts of cpu_base
  */
 static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base)
 {
         base->expires_next.tv64 = KTIME_MAX;
         base->hres_active = 0;
-        INIT_LIST_HEAD(&base->cb_pending);
 }
 
 /*
@@ -524,7 +523,6 @@ static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base)
  */
 static inline void hrtimer_init_timer_hres(struct hrtimer *timer)
 {
-        INIT_LIST_HEAD(&timer->cb_entry);
 }
 
 /*
@@ -618,10 +616,13 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
 {
         return 0;
 }
-static inline int hrtimer_cb_pending(struct hrtimer *timer) { return 0; }
-static inline void hrtimer_remove_cb_pending(struct hrtimer *timer) { }
 static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
 static inline void hrtimer_init_timer_hres(struct hrtimer *timer) { }
+static inline int hrtimer_reprogram(struct hrtimer *timer,
+                                    struct hrtimer_clock_base *base)
+{
+        return 0;
+}
 
 #endif /* CONFIG_HIGH_RES_TIMERS */
 
@@ -1001,6 +1002,7 @@ void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
                 clock_id = CLOCK_MONOTONIC;
 
         timer->base = &cpu_base->clock_base[clock_id];
+        INIT_LIST_HEAD(&timer->cb_entry);
         hrtimer_init_timer_hres(timer);
 
 #ifdef CONFIG_TIMER_STATS
@@ -1030,6 +1032,85 @@ int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
 }
 EXPORT_SYMBOL_GPL(hrtimer_get_res);
 
+static void run_hrtimer_pending(struct hrtimer_cpu_base *cpu_base)
+{
+        spin_lock_irq(&cpu_base->lock);
+
+        while (!list_empty(&cpu_base->cb_pending)) {
+                enum hrtimer_restart (*fn)(struct hrtimer *);
+                struct hrtimer *timer;
+                int restart;
+
+                timer = list_entry(cpu_base->cb_pending.next,
+                                   struct hrtimer, cb_entry);
+
+                timer_stats_account_hrtimer(timer);
+
+                fn = timer->function;
+                __remove_hrtimer(timer, timer->base, HRTIMER_STATE_CALLBACK, 0);
+                spin_unlock_irq(&cpu_base->lock);
+
+                restart = fn(timer);
+
+                spin_lock_irq(&cpu_base->lock);
+
+                timer->state &= ~HRTIMER_STATE_CALLBACK;
+                if (restart == HRTIMER_RESTART) {
+                        BUG_ON(hrtimer_active(timer));
+                        /*
+                         * Enqueue the timer, allow reprogramming of the event
+                         * device
+                         */
+                        enqueue_hrtimer(timer, timer->base, 1);
+                } else if (hrtimer_active(timer)) {
+                        /*
+                         * If the timer was rearmed on another CPU, reprogram
+                         * the event device.
+                         */
+                        if (timer->base->first == &timer->node)
+                                hrtimer_reprogram(timer, timer->base);
+                }
+        }
+        spin_unlock_irq(&cpu_base->lock);
+}
+
+static void __run_hrtimer(struct hrtimer *timer)
+{
+        struct hrtimer_clock_base *base = timer->base;
+        struct hrtimer_cpu_base *cpu_base = base->cpu_base;
+        enum hrtimer_restart (*fn)(struct hrtimer *);
+        int restart;
+
+        __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
+        timer_stats_account_hrtimer(timer);
+
+        fn = timer->function;
+        if (timer->cb_mode == HRTIMER_CB_IRQSAFE_NO_SOFTIRQ) {
+                /*
+                 * Used for scheduler timers, avoid lock inversion with
+                 * rq->lock and tasklist_lock.
+                 *
+                 * These timers are required to deal with enqueue expiry
+                 * themselves and are not allowed to migrate.
+                 */
+                spin_unlock(&cpu_base->lock);
+                restart = fn(timer);
+                spin_lock(&cpu_base->lock);
+        } else
+                restart = fn(timer);
+
+        /*
+         * Note: We clear the CALLBACK bit after enqueue_hrtimer to avoid
+         * reprogramming of the event hardware. This happens at the end of this
+         * function anyway.
+         */
+        if (restart != HRTIMER_NORESTART) {
+                BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
+                enqueue_hrtimer(timer, base, 0);
+        }
+        timer->state &= ~HRTIMER_STATE_CALLBACK;
+}
+
 #ifdef CONFIG_HIGH_RES_TIMERS
 
 /*
@@ -1063,9 +1144,7 @@ void hrtimer_interrupt(struct clock_event_device *dev)
                 basenow = ktime_add(now, base->offset);
 
                 while ((node = base->first)) {
-                        enum hrtimer_restart (*fn)(struct hrtimer *);
                         struct hrtimer *timer;
-                        int restart;
 
                         timer = rb_entry(node, struct hrtimer, node);
 
@@ -1089,37 +1168,7 @@ void hrtimer_interrupt(struct clock_event_device *dev)
                                 continue;
                         }
 
-                        __remove_hrtimer(timer, base,
-                                         HRTIMER_STATE_CALLBACK, 0);
-                        timer_stats_account_hrtimer(timer);
-
-                        fn = timer->function;
-                        if (timer->cb_mode == HRTIMER_CB_IRQSAFE_NO_SOFTIRQ) {
-                                /*
-                                 * Used for scheduler timers, avoid lock
-                                 * inversion with rq->lock and tasklist_lock.
-                                 *
-                                 * These timers are required to deal with
-                                 * enqueue expiry themselves and are not
-                                 * allowed to migrate.
-                                 */
-                                spin_unlock(&cpu_base->lock);
-                                restart = fn(timer);
-                                spin_lock(&cpu_base->lock);
-                        } else
-                                restart = fn(timer);
-
-                        /*
-                         * Note: We clear the CALLBACK bit after
-                         * enqueue_hrtimer to avoid reprogramming of
-                         * the event hardware. This happens at the end
-                         * of this function anyway.
-                         */
-                        if (restart != HRTIMER_NORESTART) {
-                                BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
-                                enqueue_hrtimer(timer, base, 0);
-                        }
-                        timer->state &= ~HRTIMER_STATE_CALLBACK;
+                        __run_hrtimer(timer);
                 }
                 spin_unlock(&cpu_base->lock);
                 base++;
@@ -1140,52 +1189,41 @@ void hrtimer_interrupt(struct clock_event_device *dev)
 
 static void run_hrtimer_softirq(struct softirq_action *h)
 {
-        struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
-
-        spin_lock_irq(&cpu_base->lock);
-
-        while (!list_empty(&cpu_base->cb_pending)) {
-                enum hrtimer_restart (*fn)(struct hrtimer *);
-                struct hrtimer *timer;
-                int restart;
-
-                timer = list_entry(cpu_base->cb_pending.next,
-                                   struct hrtimer, cb_entry);
+        run_hrtimer_pending(&__get_cpu_var(hrtimer_bases));
+}
 
-                timer_stats_account_hrtimer(timer);
+#endif  /* CONFIG_HIGH_RES_TIMERS */
 
-                fn = timer->function;
-                __remove_hrtimer(timer, timer->base, HRTIMER_STATE_CALLBACK, 0);
-                spin_unlock_irq(&cpu_base->lock);
+/*
+ * Called from timer softirq every jiffy, expire hrtimers:
+ *
+ * For HRT its the fall back code to run the softirq in the timer
+ * softirq context in case the hrtimer initialization failed or has
+ * not been done yet.
+ */
+void hrtimer_run_pending(void)
+{
+        struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
 
-                restart = fn(timer);
+        if (hrtimer_hres_active())
+                return;
 
-                spin_lock_irq(&cpu_base->lock);
+        /*
+         * This _is_ ugly: We have to check in the softirq context,
+         * whether we can switch to highres and / or nohz mode. The
+         * clocksource switch happens in the timer interrupt with
+         * xtime_lock held. Notification from there only sets the
+         * check bit in the tick_oneshot code, otherwise we might
+         * deadlock vs. xtime_lock.
+         */
+        if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
+                hrtimer_switch_to_hres();
 
-                timer->state &= ~HRTIMER_STATE_CALLBACK;
-                if (restart == HRTIMER_RESTART) {
-                        BUG_ON(hrtimer_active(timer));
-                        /*
-                         * Enqueue the timer, allow reprogramming of the event
-                         * device
-                         */
-                        enqueue_hrtimer(timer, timer->base, 1);
-                } else if (hrtimer_active(timer)) {
-                        /*
-                         * If the timer was rearmed on another CPU, reprogram
-                         * the event device.
-                         */
-                        if (timer->base->first == &timer->node)
-                                hrtimer_reprogram(timer, timer->base);
-                }
-        }
-        spin_unlock_irq(&cpu_base->lock);
+        run_hrtimer_pending(cpu_base);
 }
 
-#endif  /* CONFIG_HIGH_RES_TIMERS */
-
 /*
- * Expire the per base hrtimer-queue:
+ * Called from hardirq context every jiffy
  */
 static inline void run_hrtimer_queue(struct hrtimer_cpu_base *cpu_base,
                                      int index)
@@ -1199,46 +1237,27 @@ static inline void run_hrtimer_queue(struct hrtimer_cpu_base *cpu_base,
         if (base->get_softirq_time)
                 base->softirq_time = base->get_softirq_time();
 
-        spin_lock_irq(&cpu_base->lock);
+        spin_lock(&cpu_base->lock);
 
         while ((node = base->first)) {
                 struct hrtimer *timer;
-                enum hrtimer_restart (*fn)(struct hrtimer *);
-                int restart;
 
                 timer = rb_entry(node, struct hrtimer, node);
                 if (base->softirq_time.tv64 <= timer->expires.tv64)
                         break;
 
-#ifdef CONFIG_HIGH_RES_TIMERS
-                WARN_ON_ONCE(timer->cb_mode == HRTIMER_CB_IRQSAFE_NO_SOFTIRQ);
-#endif
-                timer_stats_account_hrtimer(timer);
-
-                fn = timer->function;
-                __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
-                spin_unlock_irq(&cpu_base->lock);
-
-                restart = fn(timer);
-
-                spin_lock_irq(&cpu_base->lock);
-
-                timer->state &= ~HRTIMER_STATE_CALLBACK;
-                if (restart != HRTIMER_NORESTART) {
-                        BUG_ON(hrtimer_active(timer));
-                        enqueue_hrtimer(timer, base, 0);
+                if (timer->cb_mode == HRTIMER_CB_SOFTIRQ) {
+                        __remove_hrtimer(timer, base, HRTIMER_STATE_PENDING, 0);
+                        list_add_tail(&timer->cb_entry,
+                                        &base->cpu_base->cb_pending);
+                        continue;
                 }
+
+                __run_hrtimer(timer);
         }
-        spin_unlock_irq(&cpu_base->lock);
+        spin_unlock(&cpu_base->lock);
 }
 
-/*
- * Called from timer softirq every jiffy, expire hrtimers:
- *
- * For HRT its the fall back code to run the softirq in the timer
- * softirq context in case the hrtimer initialization failed or has
- * not been done yet.
- */
 void hrtimer_run_queues(void)
 {
         struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
@@ -1247,18 +1266,6 @@ void hrtimer_run_queues(void)
         if (hrtimer_hres_active())
                 return;
 
-        /*
-         * This _is_ ugly: We have to check in the softirq context,
-         * whether we can switch to highres and / or nohz mode. The
-         * clocksource switch happens in the timer interrupt with
-         * xtime_lock held. Notification from there only sets the
-         * check bit in the tick_oneshot code, otherwise we might
-         * deadlock vs. xtime_lock.
-         */
-        if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
-                if (hrtimer_switch_to_hres())
-                        return;
-
         hrtimer_get_softirq_time(cpu_base);
 
         for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
@@ -1407,6 +1414,7 @@ static void __cpuinit init_hrtimers_cpu(int cpu)
         for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
                 cpu_base->clock_base[i].cpu_base = cpu_base;
 
+        INIT_LIST_HEAD(&cpu_base->cb_pending);
         hrtimer_init_hres(cpu_base);
 }
 
diff --git a/kernel/timer.c b/kernel/timer.c
index 2a00c22203f3..f739dfb539ce 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -896,7 +896,7 @@ static void run_timer_softirq(struct softirq_action *h)
 {
         tvec_base_t *base = __get_cpu_var(tvec_bases);
 
-        hrtimer_run_queues();
+        hrtimer_run_pending();
 
         if (time_after_eq(jiffies, base->timer_jiffies))
                 __run_timers(base);
@@ -907,6 +907,7 @@ static void run_timer_softirq(struct softirq_action *h)
  */
 void run_local_timers(void)
 {
+        hrtimer_run_queues();
         raise_softirq(TIMER_SOFTIRQ);
         softlockup_tick();
 }