[PATCH] clockevents: Fix suspend/resume to disk hangs

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 51 insertions, 12 deletions

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 5567745470f7..eadfce2fff74 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 43ba1bdec14c..bfda3f7f0716 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 75890efd24ff..c9d203bde518 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 2e8b7ff863cc..f6997ab0c3c9 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,