* Linus Torvalds <torvalds@linux-foundation.org> wrote:

quoted text
> > Compiling right now - delayed because I just had to pick up one of 
> > the kids from gymnastics.
> 
> Ok, it does indeed solve the problem for me.
> 
> Mind sending a signed-off thing with explanations etc?

here's Thomas' patch with explanations:

------------------------->
From: Thomas Gleixner <tglx@linutronix.de>

The programming of periodic tick devices needs to be saved/restored 
across suspend/resume - otherwise we might end up with a system coming 
up that relies on getting a PIT (or HPET) interrupt, while those devices 
default to 'no interrupts' after powerup. (To confuse things it worked 
to a certain degree on some systems because the lapic gets initialized 
as a side-effect of SMP bootup.)

This suspend / resume thing was dropped unintentionally during the 
last-minute -mm code reshuffling.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 12b3efe..5567745 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -284,6 +284,42 @@ void tick_shutdown_broadcast(unsigned int *cpup)
 	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 }
 
+void tick_suspend_broadcast(void)
+{
+	struct clock_event_device *bc;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tick_broadcast_lock, flags);
+
+	bc = tick_broadcast_device.evtdev;
+	if (bc && tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
+		clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
+
+	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
+}
+
+int tick_resume_broadcast(void)
+{
+	struct clock_event_device *bc;
+	unsigned long flags;
+	int broadcast = 0;
+
+	spin_lock_irqsave(&tick_broadcast_lock, flags);
+
+	bc = tick_broadcast_device.evtdev;
+	if (bc) {
+		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC &&
+		    !cpus_empty(tick_broadcast_mask))
+			tick_broadcast_start_periodic(bc);
+
+		broadcast = cpu_isset(smp_processor_id(), tick_broadcast_mask);
+	}
+	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
+
+	return broadcast;
+}
+
+
 #ifdef CONFIG_TICK_ONESHOT
 
 static cpumask_t tick_broadcast_oneshot_mask;
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 0986a2b..43ba1bd 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -298,6 +298,28 @@ static void tick_shutdown(unsigned int *cpup)
 	spin_unlock_irqrestore(&tick_device_lock, flags);
 }
 
+static void tick_suspend_periodic(void)
+{
+	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
+	unsigned long flags;
+
+	spin_lock_irqsave(&tick_device_lock, flags);
+	if (td->mode == TICKDEV_MODE_PERIODIC)
+		clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
+	spin_unlock_irqrestore(&tick_device_lock, flags);
+}
+
+static void tick_resume_periodic(void)
+{
+	struct tick_device *td = &__get_cpu_var(tick_cpu_device);
+	unsigned long flags;
+
+	spin_lock_irqsave(&tick_device_lock, flags);
+	if (td->mode == TICKDEV_MODE_PERIODIC)
+		tick_setup_periodic(td->evtdev, 0);
+	spin_unlock_irqrestore(&tick_device_lock, flags);
+}
+
 /*
  * Notification about clock event devices
  */
@@ -325,6 +347,16 @@ static int tick_notify(struct notifier_block *nb, unsigned long reason,
 		tick_shutdown(dev);
 		break;
 
+	case CLOCK_EVT_NOTIFY_SUSPEND:
+		tick_suspend_periodic();
+		tick_suspend_broadcast();
+		break;
+
+	case CLOCK_EVT_NOTIFY_RESUME:
+		if (!tick_resume_broadcast())
+			tick_resume_periodic();
+		break;
+
 	default:
 		break;
 	}
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 54861a0..75890ef 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -67,6 +67,8 @@ extern int tick_check_broadcast_device(struct clock_event_device *dev);
 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_set_periodic_handler(struct clock_event_device *dev, int broadcast);
@@ -90,6 +92,8 @@ static inline int tick_device_uses_broadcast(struct clock_event_device *dev,
 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; }
 
 /*
  * Set the periodic handler in non broadcast mode
diff --git a/kernel/timer.c b/kernel/timer.c
index 6663a87..718437f 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -997,6 +997,9 @@ static int timekeeping_resume(struct sys_device *dev)
 	write_sequnlock_irqrestore(&xtime_lock, flags);
 
 	touch_softlockup_watchdog();
+
+	clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
+
 	/* Resume hrtimers */
 	clock_was_set();
 
@@ -1011,6 +1014,9 @@ static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
 	timekeeping_suspended = 1;
 	timekeeping_suspend_time = read_persistent_clock();
 	write_sequnlock_irqrestore(&xtime_lock, flags);
+
+	clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
+
 	return 0;
 }
 

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