posix-timers: Add active flag to k_itimer

Keep track of the activation state of posix timers. This is a preparatory
change for making common_timer_get() usable by both hrtimer and alarm timer
implementations.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170530211656.967783982@linutronix.de

include/linux/posix-timers.h

@@ -59,6 +59,7 @@ struct cpu_timer_list {
  * @kclock:		Pointer to the k_clock struct handling this timer
  * @it_clock:		The posix timer clock id
  * @it_id:		The posix timer id for identifying the timer
+ * @it_active:		Marker that timer is active
  * @it_overrun:		The overrun counter for pending signals
  * @it_overrun_last:	The overrun at the time of the last delivered signal
  * @it_requeue_pending:	Indicator that timer waits for being requeued on
@@ -79,6 +80,7 @@ struct k_itimer {
 	const struct k_clock	*kclock;
 	clockid_t		it_clock;
 	timer_t			it_id;
+	int			it_active;
 	int			it_overrun;
 	int			it_overrun_last;
 	int			it_requeue_pending;

kernel/time/posix-timers.c

@@ -316,6 +316,7 @@ void posixtimer_rearm(struct siginfo *info)
 	if (timr->it_requeue_pending == info->si_sys_private) {
 		timr->kclock->timer_rearm(timr);
 
+		timr->it_active = 1;
 		timr->it_overrun_last = timr->it_overrun;
 		timr->it_overrun = -1;
 		++timr->it_requeue_pending;
@@ -371,6 +372,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
 	timr = container_of(timer, struct k_itimer, it.real.timer);
 	spin_lock_irqsave(&timr->it_lock, flags);
 
+	timr->it_active = 0;
 	if (timr->it_interval != 0)
 		si_private = ++timr->it_requeue_pending;
 
@@ -418,6 +420,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
 						timr->it_interval);
 			ret = HRTIMER_RESTART;
 			++timr->it_requeue_pending;
+			timr->it_active = 1;
 		}
 	}
 
@@ -737,7 +740,8 @@ common_timer_set(struct k_itimer *timr, int flags,
 	if (hrtimer_try_to_cancel(timer) < 0)
 		return TIMER_RETRY;
 
-	timr->it_requeue_pending = (timr->it_requeue_pending + 2) & 
+	timr->it_active = 0;
+	timr->it_requeue_pending = (timr->it_requeue_pending + 2) &
 		~REQUEUE_PENDING;
 	timr->it_overrun_last = 0;
 
@@ -763,6 +767,7 @@ common_timer_set(struct k_itimer *timr, int flags,
 		return 0;
 	}
 
+	timr->it_active = 1;
 	hrtimer_start_expires(timer, mode);
 	return 0;
 }
@@ -821,6 +826,7 @@ static int common_timer_del(struct k_itimer *timer)
 
 	if (hrtimer_try_to_cancel(&timer->it.real.timer) < 0)
 		return TIMER_RETRY;
+	timer->it_active = 0;
 	return 0;
 }