[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>

kernel/time/tick-oneshot.c

@@ -40,6 +40,18 @@ 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)
  */