clockevents: prevent endless loop in periodic broadcast handler

commit d4496b39559c6d43f83e4c08b899984f8b8089b5 upstream

The reprogramming of the periodic broadcast handler was broken,
when the first programming returned -ETIME. The clockevents code
stores the new expiry value in the clock events device next_event field
only when the programming time has not been elapsed yet. The loop in
question calculates the new expiry value from the next_event value
and therefor never increases.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index e1bd50cbbf5d232896b4ae470bf005adb84e543d..910b3d33867b5e9c3872cba30116d8a057934f2d 100644 (file)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -174,6 +174,8 @@ static void tick_do_periodic_broadcast(void)
  */
 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 {
+       ktime_t next;
+
        tick_do_periodic_broadcast();
 
        /*
@@ -184,10 +186,13 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 
        /*
         * Setup the next period for devices, which do not have
-        * periodic mode:
+        * periodic mode. We read dev->next_event first and add to it
+        * when the event alrady expired. clockevents_program_event()
+        * sets dev->next_event only when the event is really
+        * programmed to the device.
         */
-       for (;;) {
-               ktime_t next = ktime_add(dev->next_event, tick_period);
+       for (next = dev->next_event; ;) {
+               next = ktime_add(next, tick_period);
 
                if (!clockevents_program_event(dev, next, ktime_get()))
                        return;