alarmtimers: Add alarm_forward functionality
In order to avoid wasting time expiring and re-adding very high freq
periodic alarmtimers, introduce alarm_forward() which is similar to
hrtimer_forward and moves the timer to the next future expiration time
and returns the number of overruns.
CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 55e634e..f03b042 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -347,6 +347,41 @@
}
+
+u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval)
+{
+ u64 overrun = 1;
+ ktime_t delta;
+
+ delta = ktime_sub(now, alarm->node.expires);
+
+ if (delta.tv64 < 0)
+ return 0;
+
+ if (unlikely(delta.tv64 >= interval.tv64)) {
+ s64 incr = ktime_to_ns(interval);
+
+ overrun = ktime_divns(delta, incr);
+
+ alarm->node.expires = ktime_add_ns(alarm->node.expires,
+ incr*overrun);
+
+ if (alarm->node.expires.tv64 > now.tv64)
+ return overrun;
+ /*
+ * This (and the ktime_add() below) is the
+ * correction for exact:
+ */
+ overrun++;
+ }
+
+ alarm->node.expires = ktime_add(alarm->node.expires, interval);
+ return overrun;
+}
+
+
+
+
/**
* clock2alarm - helper that converts from clockid to alarmtypes
* @clockid: clockid.
@@ -376,7 +411,7 @@
/* Re-add periodic timers */
if (alarm->period.tv64) {
- alarm->node.expires = ktime_add(now, alarm->period);
+ ptr->it_overrun += alarm_forward(alarm, now, alarm->period);
return ALARMTIMER_RESTART;
}
return ALARMTIMER_NORESTART;