[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>

1 files changed, 22 insertions, 5 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:
  *