alarmtimers: Change alarmtimer functions to return alarmtimer_restart values

In order to properly fix the denial of service issue with high freq
periodic alarm timers, we need to push the re-arming logic into the
alarm timer handler, much as the hrtimer code does.

This patch introduces alarmtimer_restart enum and changes the
alarmtimer handler declarations to use it as a return value. Further,
to ease following changes, it extends the alarmtimer handler functions
to also take the time at expiration. No logic is yet modified.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/linux/alarmtimer.h b/include/linux/alarmtimer.h
index c5d6095b46f8..0289eb29e794 100644
--- a/include/linux/alarmtimer.h
+++ b/include/linux/alarmtimer.h
@@ -13,6 +13,11 @@ enum alarmtimer_type {
         ALARM_NUMTYPE,
 };
 
+enum alarmtimer_restart {
+        ALARMTIMER_NORESTART,
+        ALARMTIMER_RESTART,
+};
+
 /**
  * struct alarm - Alarm timer structure
  * @node:       timerqueue node for adding to the event list this value
@@ -26,14 +31,14 @@ enum alarmtimer_type {
 struct alarm {
         struct timerqueue_node  node;
         ktime_t                 period;
-        void                    (*function)(struct alarm *);
+        enum alarmtimer_restart (*function)(struct alarm *, ktime_t now);
         enum alarmtimer_type    type;
         bool                    enabled;
         void                    *data;
 };
 
 void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
-                void (*function)(struct alarm *));
+                enum alarmtimer_restart (*function)(struct alarm *, ktime_t));
 void alarm_start(struct alarm *alarm, ktime_t start, ktime_t period);
 void alarm_cancel(struct alarm *alarm);