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Subject[PATCH] clockevents: Fix suspend/resume to disk hangs
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Date
I finally found a dual core box, which survives suspend/resume without
crashing in the middle of nowhere. Sigh, I never figured out from the
code and the bug reports what's going on.

The observed hangs are caused by a stale state transition of the clock
event devices, which keeps the RCU synchronization away from completion,
when the non boot CPU is brought back up.

The suspend/resume in oneshot mode needs the similar care as the
periodic mode during suspend to RAM. My assumption that the state
transitions during the different shutdown/bringups of s2disk would go
through the periodic boot phase and then switch over to highres resp.
nohz mode were simply wrong.

Add the appropriate suspend / resume handling for the non periodic
modes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 5567745..eadfce2 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -307,12 +307,19 @@ int tick_resume_broadcast(void)
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);
+ if (bc) {
+ switch (tick_broadcast_device.mode) {
+ case TICKDEV_MODE_PERIODIC:
+ if(!cpus_empty(tick_broadcast_mask))
+ tick_broadcast_start_periodic(bc);
+ broadcast = cpu_isset(smp_processor_id(),
+ tick_broadcast_mask);
+ break;
+ case TICKDEV_MODE_ONESHOT:
+ broadcast = tick_resume_broadcast_oneshot(bc);
+ break;
+ }
}
spin_unlock_irqrestore(&tick_broadcast_lock, flags);

@@ -347,6 +354,16 @@ static int tick_broadcast_set_event(ktime_t expires, int force)
}
}

+int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
+{
+ clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
+
+ if(!cpus_empty(tick_broadcast_oneshot_mask))
+ tick_broadcast_set_event(ktime_get(), 1);
+
+ return cpu_isset(smp_processor_id(), tick_broadcast_oneshot_mask);
+}
+
/*
* Reprogram the broadcast device:
*
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 43ba1bd..bfda3f7 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -298,18 +298,17 @@ static void tick_shutdown(unsigned int *cpup)
spin_unlock_irqrestore(&tick_device_lock, flags);
}

-static void tick_suspend_periodic(void)
+static void tick_suspend(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);
+ clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
spin_unlock_irqrestore(&tick_device_lock, flags);
}

-static void tick_resume_periodic(void)
+static void tick_resume(void)
{
struct tick_device *td = &__get_cpu_var(tick_cpu_device);
unsigned long flags;
@@ -317,6 +316,8 @@ static void tick_resume_periodic(void)
spin_lock_irqsave(&tick_device_lock, flags);
if (td->mode == TICKDEV_MODE_PERIODIC)
tick_setup_periodic(td->evtdev, 0);
+ else
+ tick_resume_oneshot();
spin_unlock_irqrestore(&tick_device_lock, flags);
}

@@ -348,13 +349,13 @@ static int tick_notify(struct notifier_block *nb, unsigned long reason,
break;

case CLOCK_EVT_NOTIFY_SUSPEND:
- tick_suspend_periodic();
+ tick_suspend();
tick_suspend_broadcast();
break;

case CLOCK_EVT_NOTIFY_RESUME:
if (!tick_resume_broadcast())
- tick_resume_periodic();
+ tick_resume();
break;

default:
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 75890ef..c9d203b 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -19,12 +19,13 @@ extern void tick_setup_oneshot(struct clock_event_device *newdev,
extern int tick_program_event(ktime_t expires, int force);
extern void tick_oneshot_notify(void);
extern int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *));
-
+extern void tick_resume_oneshot(void);
# ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
extern void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
extern void tick_broadcast_oneshot_control(unsigned long reason);
extern void tick_broadcast_switch_to_oneshot(void);
extern void tick_shutdown_broadcast_oneshot(unsigned int *cpup);
+extern int tick_resume_broadcast_oneshot(struct clock_event_device *bc);
# else /* BROADCAST */
static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
{
@@ -43,6 +44,10 @@ void tick_setup_oneshot(struct clock_event_device *newdev,
{
BUG();
}
+static inline void tick_resume_oneshot(void)
+{
+ BUG();
+}
static inline int tick_program_event(ktime_t expires, int force)
{
return 0;
@@ -54,6 +59,10 @@ static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
}
static inline void tick_broadcast_oneshot_control(unsigned long reason) { }
static inline void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { }
+static inline int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
+{
+ return 0;
+}
#endif /* !TICK_ONESHOT */

/*
diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c
index 2e8b7ff..f6997ab 100644
--- a/kernel/time/tick-oneshot.c
+++ b/kernel/time/tick-oneshot.c
@@ -41,6 +41,18 @@ int tick_program_event(ktime_t expires, int force)
}

/**
+ * tick_resume_onshot - resume oneshot mode
+ */
+void tick_resume_oneshot(void)
+{
+ struct tick_device *td = &__get_cpu_var(tick_cpu_device);
+ struct clock_event_device *dev = td->evtdev;
+
+ clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
+ tick_program_event(ktime_get(), 1);
+}
+
+/**
* tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
*/
void tick_setup_oneshot(struct clock_event_device *newdev,

-
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