tick/xen: Provide and use tick_suspend_local() and tick_resume_local()

Xen calls on every cpu into tick_resume() which is just wrong.
tick_resume() is for the syscore global suspend/resume
invocation. What XEN really wants is a per cpu local resume
function.

Provide a tick_resume_local() function and use it in XEN.

Also provide a complementary tick_suspend_local() and modify
tick_unfreeze() and tick_freeze(), respectively, to use the
new local tick resume/suspend functions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ Combined two patches, rebased, modified subject/changelog. ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1698741.eezk9tnXtG@vostro.rjw.lan
[ Merged to latest timers/core. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/xen/suspend.c

@@ -85,7 +85,7 @@ static void xen_vcpu_notify_restore(void *data)
 	if (smp_processor_id() == 0)
 		return;
 
-	tick_resume();
+	tick_resume_local();
 }
 
 void xen_arch_resume(void)

include/linux/tick.h

@@ -29,13 +29,13 @@ extern struct tick_device *tick_get_device(int cpu);
 extern void __init tick_init(void);
 extern void tick_freeze(void);
 extern void tick_unfreeze(void);
-/* Should be core only, but XEN resume magic abuses this interface */
-extern void tick_resume(void);
+/* Should be core only, but XEN resume magic requires this */
+extern void tick_resume_local(void);
 #else /* CONFIG_GENERIC_CLOCKEVENTS */
 static inline void tick_init(void) { }
 static inline void tick_freeze(void) { }
 static inline void tick_unfreeze(void) { }
-static inline void tick_resume(void) { }
+static inline void tick_resume_local(void) { }
 #endif /* !CONFIG_GENERIC_CLOCKEVENTS */
 
 #ifdef CONFIG_TICK_ONESHOT

kernel/time/tick-broadcast.c

@@ -455,11 +455,26 @@ void tick_suspend_broadcast(void)
 	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 }
 
-int tick_resume_broadcast(void)
+/*
+ * This is called from tick_resume_local() on a resuming CPU. That's
+ * called from the core resume function, tick_unfreeze() and the magic XEN
+ * resume hackery.
+ *
+ * In none of these cases the broadcast device mode can change and the
+ * bit of the resuming CPU in the broadcast mask is safe as well.
+ */
+bool tick_resume_check_broadcast(void)
+{
+	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
+		return false;
+	else
+		return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
+}
+
+void tick_resume_broadcast(void)
 {
 	struct clock_event_device *bc;
 	unsigned long flags;
-	int broadcast = 0;
 
 	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 
@@ -472,8 +487,6 @@ int tick_resume_broadcast(void)
 		case TICKDEV_MODE_PERIODIC:
 			if (!cpumask_empty(tick_broadcast_mask))
 				tick_broadcast_start_periodic(bc);
-			broadcast = cpumask_test_cpu(smp_processor_id(),
-						     tick_broadcast_mask);
 			break;
 		case TICKDEV_MODE_ONESHOT:
 			if (!cpumask_empty(tick_broadcast_mask))
@@ -482,11 +495,8 @@ int tick_resume_broadcast(void)
 		}
 	}
 	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
-
-	return broadcast;
 }
 
-
 #ifdef CONFIG_TICK_ONESHOT
 
 static cpumask_var_t tick_broadcast_oneshot_mask;

kernel/time/tick-common.c

@@ -373,6 +373,41 @@ void tick_shutdown(unsigned int *cpup)
 	}
 }
 
+/**
+ * tick_suspend_local - Suspend the local tick device
+ *
+ * Called from the local cpu for freeze with interrupts disabled.
+ *
+ * No locks required. Nothing can change the per cpu device.
+ */
+static void tick_suspend_local(void)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+
+	clockevents_shutdown(td->evtdev);
+}
+
+/**
+ * tick_resume_local - Resume the local tick device
+ *
+ * Called from the local CPU for unfreeze or XEN resume magic.
+ *
+ * No locks required. Nothing can change the per cpu device.
+ */
+void tick_resume_local(void)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+	bool broadcast = tick_resume_check_broadcast();
+
+	clockevents_tick_resume(td->evtdev);
+	if (!broadcast) {
+		if (td->mode == TICKDEV_MODE_PERIODIC)
+			tick_setup_periodic(td->evtdev, 0);
+		else
+			tick_resume_oneshot();
+	}
+}
+
 /**
  * tick_suspend - Suspend the tick and the broadcast device
  *
@@ -384,9 +419,7 @@ void tick_shutdown(unsigned int *cpup)
  */
 void tick_suspend(void)
 {
-	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
-
-	clockevents_shutdown(td->evtdev);
+	tick_suspend_local();
 	tick_suspend_broadcast();
 }
 
@@ -394,26 +427,14 @@ void tick_suspend(void)
  * tick_resume - Resume the tick and the broadcast device
  *
  * Called from syscore_resume() via timekeeping_resume with only one
- * CPU online and interrupts disabled or from tick_unfreeze() under
- * tick_freeze_lock.
+ * CPU online and interrupts disabled.
  *
  * No locks required. Nothing can change the per cpu device.
  */
 void tick_resume(void)
 {
-	struct tick_device *td;
-	int broadcast;
-
-	broadcast = tick_resume_broadcast();
-	td = this_cpu_ptr(&tick_cpu_device);
-	clockevents_tick_resume(td->evtdev);
-
-	if (!broadcast) {
-		if (td->mode == TICKDEV_MODE_PERIODIC)
-			tick_setup_periodic(td->evtdev, 0);
-		else
-			tick_resume_oneshot();
-	}
+	tick_resume_broadcast();
+	tick_resume_local();
 }
 
 static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
@@ -436,7 +457,7 @@ void tick_freeze(void)
 	if (tick_freeze_depth == num_online_cpus()) {
 		timekeeping_suspend();
 	} else {
-		tick_suspend();
+		tick_suspend_local();
 	}
 
 	raw_spin_unlock(&tick_freeze_lock);

kernel/time/tick-internal.h

@@ -23,6 +23,7 @@ extern void tick_check_new_device(struct clock_event_device *dev);
 extern void tick_handover_do_timer(int *cpup);
 extern void tick_shutdown(unsigned int *cpup);
 extern void tick_suspend(void);
+extern void tick_resume(void);
 extern bool tick_check_replacement(struct clock_event_device *curdev,
 				   struct clock_event_device *newdev);
 extern void tick_install_replacement(struct clock_event_device *dev);
@@ -43,6 +44,7 @@ extern int __clockevents_update_freq(struct clock_event_device *dev, u32 freq);
 extern ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt);
 #else
 static inline void tick_suspend(void) { }
+static inline void tick_resume(void) { }
 #endif /* GENERIC_CLOCKEVENTS */
 
 /* Oneshot related functions */
@@ -81,7 +83,8 @@ extern int tick_is_broadcast_device(struct clock_event_device *dev);
 extern void tick_broadcast_on_off(unsigned long reason, int *oncpu);
 extern void tick_shutdown_broadcast(unsigned int *cpup);
 extern void tick_suspend_broadcast(void);
-extern int tick_resume_broadcast(void);
+extern void tick_resume_broadcast(void);
+extern bool tick_resume_check_broadcast(void);
 extern void tick_broadcast_init(void);
 extern void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast);
 extern int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq);
@@ -95,7 +98,8 @@ static inline void tick_do_periodic_broadcast(struct clock_event_device *d) { }
 static inline void tick_broadcast_on_off(unsigned long reason, int *oncpu) { }
 static inline void tick_shutdown_broadcast(unsigned int *cpup) { }
 static inline void tick_suspend_broadcast(void) { }
-static inline int tick_resume_broadcast(void) { return 0; }
+static inline void tick_resume_broadcast(void) { }
+static inline bool tick_resume_check_broadcast(void) { return false; }
 static inline void tick_broadcast_init(void) { }
 static inline int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq) { return -ENODEV; }