1 files changed, 306 insertions, 77 deletions

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 803fa67aace9..0207868c8b4d 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -33,13 +33,22 @@ static int tick_broadcast_forced;
 static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
 
 #ifdef CONFIG_TICK_ONESHOT
-static void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
+static DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);
+
+static void tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic);
 static void tick_broadcast_clear_oneshot(int cpu);
 static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
+# ifdef CONFIG_HOTPLUG_CPU
+static void tick_broadcast_oneshot_offline(unsigned int cpu);
+# endif
 #else
-static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { BUG(); }
+static inline void
+tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic) { BUG(); }
 static inline void tick_broadcast_clear_oneshot(int cpu) { }
 static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
+# ifdef CONFIG_HOTPLUG_CPU
+static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
+# endif
 #endif
 
 /*
@@ -55,6 +64,13 @@ struct cpumask *tick_get_broadcast_mask(void)
 	return tick_broadcast_mask;
 }
 
+static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);
+
+const struct clock_event_device *tick_get_wakeup_device(int cpu)
+{
+	return tick_get_oneshot_wakeup_device(cpu);
+}
+
 /*
  * Start the device in periodic mode
  */
@@ -82,13 +98,75 @@ static bool tick_check_broadcast_device(struct clock_event_device *curdev,
 	return !curdev || newdev->rating > curdev->rating;
 }
 
+#ifdef CONFIG_TICK_ONESHOT
+static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
+{
+	return per_cpu(tick_oneshot_wakeup_device, cpu);
+}
+
+static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
+{
+	/*
+	 * If we woke up early and the tick was reprogrammed in the
+	 * meantime then this may be spurious but harmless.
+	 */
+	tick_receive_broadcast();
+}
+
+static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
+					   int cpu)
+{
+	struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
+
+	if (!newdev)
+		goto set_device;
+
+	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
+	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
+		 return false;
+
+	if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
+	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
+		return false;
+
+	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
+		return false;
+
+	if (curdev && newdev->rating <= curdev->rating)
+		return false;
+
+	if (!try_module_get(newdev->owner))
+		return false;
+
+	newdev->event_handler = tick_oneshot_wakeup_handler;
+set_device:
+	clockevents_exchange_device(curdev, newdev);
+	per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
+	return true;
+}
+#else
+static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
+{
+	return NULL;
+}
+
+static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
+					   int cpu)
+{
+	return false;
+}
+#endif
+
 /*
  * Conditionally install/replace broadcast device
  */
-void tick_install_broadcast_device(struct clock_event_device *dev)
+void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
 {
 	struct clock_event_device *cur = tick_broadcast_device.evtdev;
 
+	if (tick_set_oneshot_wakeup_device(dev, cpu))
+		return;
+
 	if (!tick_check_broadcast_device(cur, dev))
 		return;
 
@@ -101,6 +179,19 @@ void tick_install_broadcast_device(struct clock_event_device *dev)
 	tick_broadcast_device.evtdev = dev;
 	if (!cpumask_empty(tick_broadcast_mask))
 		tick_broadcast_start_periodic(dev);
+
+	if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
+		return;
+
+	/*
+	 * If the system already runs in oneshot mode, switch the newly
+	 * registered broadcast device to oneshot mode explicitly.
+	 */
+	if (tick_broadcast_oneshot_active()) {
+		tick_broadcast_switch_to_oneshot();
+		return;
+	}
+
 	/*
 	 * Inform all cpus about this. We might be in a situation
 	 * where we did not switch to oneshot mode because the per cpu
@@ -109,8 +200,7 @@ void tick_install_broadcast_device(struct clock_event_device *dev)
 	 * notification the systems stays stuck in periodic mode
 	 * forever.
 	 */
-	if (dev->features & CLOCK_EVT_FEAT_ONESHOT)
-		tick_clock_notify();
+	tick_clock_notify();
 }
 
 /*
@@ -151,7 +241,7 @@ static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
 }
 
 /*
- * Check, if the device is disfunctional and a place holder, which
+ * Check, if the device is dysfunctional and a placeholder, which
  * needs to be handled by the broadcast device.
  */
 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
@@ -175,7 +265,7 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 			tick_broadcast_start_periodic(bc);
 		else
-			tick_broadcast_setup_oneshot(bc);
+			tick_broadcast_setup_oneshot(bc, false);
 		ret = 1;
 	} else {
 		/*
@@ -235,7 +325,6 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 	return ret;
 }
 
-#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 int tick_receive_broadcast(void)
 {
 	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
@@ -250,7 +339,6 @@ int tick_receive_broadcast(void)
 	evt->event_handler(evt);
 	return 0;
 }
-#endif
 
 /*
  * Broadcast the event to the cpus, which are set in the mask (mangled).
@@ -325,7 +413,7 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 	bc_local = tick_do_periodic_broadcast();
 
 	if (clockevent_state_oneshot(dev)) {
-		ktime_t next = ktime_add(dev->next_event, tick_period);
+		ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
 
 		clockevents_program_event(dev, next, true);
 	}
@@ -375,6 +463,7 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
 	switch (mode) {
 	case TICK_BROADCAST_FORCE:
 		tick_broadcast_forced = 1;
+		fallthrough;
 	case TICK_BROADCAST_ON:
 		cpumask_set_cpu(cpu, tick_broadcast_on);
 		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
@@ -384,7 +473,7 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
 			 * - the broadcast device exists
 			 * - the broadcast device is not a hrtimer based one
 			 * - the broadcast device is in periodic mode to
-			 *   avoid a hickup during switch to oneshot mode
+			 *   avoid a hiccup during switch to oneshot mode
 			 */
 			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
 			    tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
@@ -412,7 +501,7 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
 			if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 				tick_broadcast_start_periodic(bc);
 			else
-				tick_broadcast_setup_oneshot(bc);
+				tick_broadcast_setup_oneshot(bc, false);
 		}
 	}
 out:
@@ -432,27 +521,29 @@ void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
-/*
- * Remove a CPU from broadcasting
- */
-void tick_shutdown_broadcast(unsigned int cpu)
+static void tick_shutdown_broadcast(void)
 {
-	struct clock_event_device *bc;
-	unsigned long flags;
-
-	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
-
-	bc = tick_broadcast_device.evtdev;
-	cpumask_clear_cpu(cpu, tick_broadcast_mask);
-	cpumask_clear_cpu(cpu, tick_broadcast_on);
+	struct clock_event_device *bc = tick_broadcast_device.evtdev;
 
 	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 		if (bc && cpumask_empty(tick_broadcast_mask))
 			clockevents_shutdown(bc);
 	}
+}
 
-	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
+/*
+ * Remove a CPU from broadcasting
+ */
+void tick_broadcast_offline(unsigned int cpu)
+{
+	raw_spin_lock(&tick_broadcast_lock);
+	cpumask_clear_cpu(cpu, tick_broadcast_mask);
+	cpumask_clear_cpu(cpu, tick_broadcast_on);
+	tick_broadcast_oneshot_offline(cpu);
+	tick_shutdown_broadcast();
+	raw_spin_unlock(&tick_broadcast_lock);
 }
+
 #endif
 
 void tick_suspend_broadcast(void)
@@ -532,9 +623,13 @@ struct cpumask *tick_get_broadcast_oneshot_mask(void)
  * to avoid a deep idle transition as we are about to get the
  * broadcast IPI right away.
  */
-int tick_check_broadcast_expired(void)
+noinstr int tick_check_broadcast_expired(void)
 {
+#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
+	return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));
+#else
 	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
+#endif
 }
 
 /*
@@ -698,24 +793,16 @@ static void broadcast_shutdown_local(struct clock_event_device *bc,
 	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
 }
 
-int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state,
+					     struct tick_device *td,
+					     int cpu)
 {
-	struct clock_event_device *bc, *dev;
-	int cpu, ret = 0;
+	struct clock_event_device *bc, *dev = td->evtdev;
+	int ret = 0;
 	ktime_t now;
 
-	/*
-	 * If there is no broadcast device, tell the caller not to go
-	 * into deep idle.
-	 */
-	if (!tick_broadcast_device.evtdev)
-		return -EBUSY;
-
-	dev = this_cpu_ptr(&tick_cpu_device)->evtdev;
-
 	raw_spin_lock(&tick_broadcast_lock);
 	bc = tick_broadcast_device.evtdev;
-	cpu = smp_processor_id();
 
 	if (state == TICK_BROADCAST_ENTER) {
 		/*
@@ -800,13 +887,13 @@ int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
 			 * either the CPU handling the broadcast
 			 * interrupt or we got woken by something else.
 			 *
-			 * We are not longer in the broadcast mask, so
+			 * We are no longer in the broadcast mask, so
 			 * if the cpu local expiry time is already
 			 * reached, we would reprogram the cpu local
 			 * timer with an already expired event.
 			 *
 			 * This can lead to a ping-pong when we return
-			 * to idle and therefor rearm the broadcast
+			 * to idle and therefore rearm the broadcast
 			 * timer before the cpu local timer was able
 			 * to fire. This happens because the forced
 			 * reprogramming makes sure that the event
@@ -844,6 +931,53 @@ out:
 	return ret;
 }
 
+static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
+				       struct tick_device *td,
+				       int cpu)
+{
+	struct clock_event_device *dev, *wd;
+
+	dev = td->evtdev;
+	if (td->mode != TICKDEV_MODE_ONESHOT)
+		return -EINVAL;
+
+	wd = tick_get_oneshot_wakeup_device(cpu);
+	if (!wd)
+		return -ENODEV;
+
+	switch (state) {
+	case TICK_BROADCAST_ENTER:
+		clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
+		clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
+		clockevents_program_event(wd, dev->next_event, 1);
+		break;
+	case TICK_BROADCAST_EXIT:
+		/* We may have transitioned to oneshot mode while idle */
+		if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
+			return -ENODEV;
+	}
+
+	return 0;
+}
+
+int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+	int cpu = smp_processor_id();
+
+	if (!tick_oneshot_wakeup_control(state, td, cpu))
+		return 0;
+
+	if (tick_broadcast_device.evtdev)
+		return ___tick_broadcast_oneshot_control(state, td, cpu);
+
+	/*
+	 * If there is no broadcast or wakeup device, tell the caller not
+	 * to go into deep idle.
+	 */
+	return -EBUSY;
+}
+
 /*
  * Reset the one shot broadcast for a cpu
  *
@@ -868,50 +1002,122 @@ static void tick_broadcast_init_next_event(struct cpumask *mask,
 	}
 }
 
+static inline ktime_t tick_get_next_period(void)
+{
+	ktime_t next;
+
+	/*
+	 * Protect against concurrent updates (store /load tearing on
+	 * 32bit). It does not matter if the time is already in the
+	 * past. The broadcast device which is about to be programmed will
+	 * fire in any case.
+	 */
+	raw_spin_lock(&jiffies_lock);
+	next = tick_next_period;
+	raw_spin_unlock(&jiffies_lock);
+	return next;
+}
+
 /**
  * tick_broadcast_setup_oneshot - setup the broadcast device
+ * @bc: the broadcast device
+ * @from_periodic: true if called from periodic mode
  */
-static void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
+static void tick_broadcast_setup_oneshot(struct clock_event_device *bc,
+					 bool from_periodic)
 {
 	int cpu = smp_processor_id();
+	ktime_t nexttick = 0;
 
 	if (!bc)
 		return;
 
-	/* Set it up only once ! */
-	if (bc->event_handler != tick_handle_oneshot_broadcast) {
-		int was_periodic = clockevent_state_periodic(bc);
-
-		bc->event_handler = tick_handle_oneshot_broadcast;
-
+	/*
+	 * When the broadcast device was switched to oneshot by the first
+	 * CPU handling the NOHZ change, the other CPUs will reach this
+	 * code via hrtimer_run_queues() -> tick_check_oneshot_change()
+	 * too. Set up the broadcast device only once!
+	 */
+	if (bc->event_handler == tick_handle_oneshot_broadcast) {
 		/*
-		 * We must be careful here. There might be other CPUs
-		 * waiting for periodic broadcast. We need to set the
-		 * oneshot_mask bits for those and program the
-		 * broadcast device to fire.
+		 * The CPU which switched from periodic to oneshot mode
+		 * set the broadcast oneshot bit for all other CPUs which
+		 * are in the general (periodic) broadcast mask to ensure
+		 * that CPUs which wait for the periodic broadcast are
+		 * woken up.
+		 *
+		 * Clear the bit for the local CPU as the set bit would
+		 * prevent the first tick_broadcast_enter() after this CPU
+		 * switched to oneshot state to program the broadcast
+		 * device.
+		 *
+		 * This code can also be reached via tick_broadcast_control(),
+		 * but this cannot avoid the tick_broadcast_clear_oneshot()
+		 * as that would break the periodic to oneshot transition of
+		 * secondary CPUs. But that's harmless as the below only
+		 * clears already cleared bits.
 		 */
+		tick_broadcast_clear_oneshot(cpu);
+		return;
+	}
+
+
+	bc->event_handler = tick_handle_oneshot_broadcast;
+	bc->next_event = KTIME_MAX;
+
+	/*
+	 * When the tick mode is switched from periodic to oneshot it must
+	 * be ensured that CPUs which are waiting for periodic broadcast
+	 * get their wake-up at the next tick.  This is achieved by ORing
+	 * tick_broadcast_mask into tick_broadcast_oneshot_mask.
+	 *
+	 * For other callers, e.g. broadcast device replacement,
+	 * tick_broadcast_oneshot_mask must not be touched as this would
+	 * set bits for CPUs which are already NOHZ, but not idle. Their
+	 * next tick_broadcast_enter() would observe the bit set and fail
+	 * to update the expiry time and the broadcast event device.
+	 */
+	if (from_periodic) {
 		cpumask_copy(tmpmask, tick_broadcast_mask);
+		/* Remove the local CPU as it is obviously not idle */
 		cpumask_clear_cpu(cpu, tmpmask);
-		cpumask_or(tick_broadcast_oneshot_mask,
-			   tick_broadcast_oneshot_mask, tmpmask);
-
-		if (was_periodic && !cpumask_empty(tmpmask)) {
-			clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
-			tick_broadcast_init_next_event(tmpmask,
-						       tick_next_period);
-			tick_broadcast_set_event(bc, cpu, tick_next_period);
-		} else
-			bc->next_event = KTIME_MAX;
-	} else {
+		cpumask_or(tick_broadcast_oneshot_mask, tick_broadcast_oneshot_mask, tmpmask);
+
 		/*
-		 * The first cpu which switches to oneshot mode sets
-		 * the bit for all other cpus which are in the general
-		 * (periodic) broadcast mask. So the bit is set and
-		 * would prevent the first broadcast enter after this
-		 * to program the bc device.
+		 * Ensure that the oneshot broadcast handler will wake the
+		 * CPUs which are still waiting for periodic broadcast.
 		 */
-		tick_broadcast_clear_oneshot(cpu);
+		nexttick = tick_get_next_period();
+		tick_broadcast_init_next_event(tmpmask, nexttick);
+
+		/*
+		 * If the underlying broadcast clock event device is
+		 * already in oneshot state, then there is nothing to do.
+		 * The device was already armed for the next tick
+		 * in tick_handle_broadcast_periodic()
+		 */
+		if (clockevent_state_oneshot(bc))
+			return;
 	}
+
+	/*
+	 * When switching from periodic to oneshot mode arm the broadcast
+	 * device for the next tick.
+	 *
+	 * If the broadcast device has been replaced in oneshot mode and
+	 * the oneshot broadcast mask is not empty, then arm it to expire
+	 * immediately in order to reevaluate the next expiring timer.
+	 * @nexttick is 0 and therefore in the past which will cause the
+	 * clockevent code to force an event.
+	 *
+	 * For both cases the programming can be avoided when the oneshot
+	 * broadcast mask is empty.
+	 *
+	 * tick_broadcast_set_event() implicitly switches the broadcast
+	 * device to oneshot state.
+	 */
+	if (!cpumask_empty(tick_broadcast_oneshot_mask))
+		tick_broadcast_set_event(bc, cpu, nexttick);
 }
 
 /*
@@ -920,14 +1126,16 @@ static void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 void tick_broadcast_switch_to_oneshot(void)
 {
 	struct clock_event_device *bc;
+	enum tick_device_mode oldmode;
 	unsigned long flags;
 
 	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 
+	oldmode = tick_broadcast_device.mode;
 	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 	bc = tick_broadcast_device.evtdev;
 	if (bc)
-		tick_broadcast_setup_oneshot(bc);
+		tick_broadcast_setup_oneshot(bc, oldmode == TICKDEV_MODE_PERIODIC);
 
 	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 }
@@ -942,6 +1150,30 @@ void hotplug_cpu__broadcast_tick_pull(int deadcpu)
 	bc = tick_broadcast_device.evtdev;
 
 	if (bc && broadcast_needs_cpu(bc, deadcpu)) {
+		/*
+		 * If the broadcast force bit of the current CPU is set,
+		 * then the current CPU has not yet reprogrammed the local
+		 * timer device to avoid a ping-pong race. See
+		 * ___tick_broadcast_oneshot_control().
+		 *
+		 * If the broadcast device is hrtimer based then
+		 * programming the broadcast event below does not have any
+		 * effect because the local clockevent device is not
+		 * running and not programmed because the broadcast event
+		 * is not earlier than the pending event of the local clock
+		 * event device. As a consequence all CPUs waiting for a
+		 * broadcast event are stuck forever.
+		 *
+		 * Detect this condition and reprogram the cpu local timer
+		 * device to avoid the starvation.
+		 */
+		if (tick_check_broadcast_expired()) {
+			struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+
+			cpumask_clear_cpu(smp_processor_id(), tick_broadcast_force_mask);
+			tick_program_event(td->evtdev->next_event, 1);
+		}
+
 		/* This moves the broadcast assignment to this CPU: */
 		clockevents_program_event(bc, bc->next_event, 1);
 	}
@@ -949,13 +1181,12 @@ void hotplug_cpu__broadcast_tick_pull(int deadcpu)
 }
 
 /*
- * Remove a dead CPU from broadcasting
+ * Remove a dying CPU from broadcasting
  */
-void tick_shutdown_broadcast_oneshot(unsigned int cpu)
+static void tick_broadcast_oneshot_offline(unsigned int cpu)
 {
-	unsigned long flags;
-
-	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
+	if (tick_get_oneshot_wakeup_device(cpu))
+		tick_set_oneshot_wakeup_device(NULL, cpu);
 
 	/*
 	 * Clear the broadcast masks for the dead cpu, but do not stop
@@ -964,8 +1195,6 @@ void tick_shutdown_broadcast_oneshot(unsigned int cpu)
 	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
 	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
 	cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
-
-	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 }
 #endif