posix-timers: Consolidate timer setup

hrtimer based and CPU timers have their own way to install the new interval
and to reset overrun and signal handling related data.

Create a helper function and do the same operation for all variants.

This also makes the handling of the interval consistent. It's only stored
when the timer is actually armed, i.e. timer->it_value != 0. Before that it
was stored unconditionally for posix CPU timers and conditionally for the
other posix timers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

kernel/time/posix-cpu-timers.c

@@ -714,21 +714,8 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 	}
 
 	unlock_task_sighand(p, &flags);
-	/*
-	 * Install the new reload setting, and
-	 * set up the signal and overrun bookkeeping.
-	 */
-	timer->it_interval = timespec64_to_ktime(new->it_interval);
 
-	/*
-	 * This acts as a modification timestamp for the timer,
-	 * so any automatic reload attempt will punt on seeing
-	 * that we have reset the timer manually.
-	 */
-	timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
-		~REQUEUE_PENDING;
-	timer->it_overrun_last = 0;
-	timer->it_overrun = -1;
+	posix_timer_set_common(timer, new);
 
 	/*
 	 * If the new expiry time was already in the past the timer was not

kernel/time/posix-timers.c

@@ -856,6 +856,23 @@ static struct k_itimer *timer_wait_running(struct k_itimer *timer,
 	return lock_timer(timer_id, flags);
 }
 
+/*
+ * Set up the new interval and reset the signal delivery data
+ */
+void posix_timer_set_common(struct k_itimer *timer, struct itimerspec64 *new_setting)
+{
+	if (new_setting->it_value.tv_sec || new_setting->it_value.tv_nsec)
+		timer->it_interval = timespec64_to_ktime(new_setting->it_interval);
+	else
+		timer->it_interval = 0;
+
+	/* Prevent reloading in case there is a signal pending */
+	timer->it_requeue_pending = (timer->it_requeue_pending + 2) & ~REQUEUE_PENDING;
+	/* Reset overrun accounting */
+	timer->it_overrun_last = 0;
+	timer->it_overrun = -1LL;
+}
+
 /* Set a POSIX.1b interval timer. */
 int common_timer_set(struct k_itimer *timr, int flags,
 		     struct itimerspec64 *new_setting,
@@ -878,16 +895,12 @@ int common_timer_set(struct k_itimer *timr, int flags,
 		return TIMER_RETRY;
 
 	timr->it_active = 0;
-	timr->it_requeue_pending = (timr->it_requeue_pending + 2) &
-		~REQUEUE_PENDING;
-	timr->it_overrun_last = 0;
-	timr->it_overrun = -1LL;
+	posix_timer_set_common(timr, new_setting);
 
-	/* Switch off the timer when it_value is zero */
+	/* Keep timer disarmed when it_value is zero */
 	if (!new_setting->it_value.tv_sec && !new_setting->it_value.tv_nsec)
 		return 0;
 
-	timr->it_interval = timespec64_to_ktime(new_setting->it_interval);
 	expires = timespec64_to_ktime(new_setting->it_value);
 	if (flags & TIMER_ABSTIME)
 		expires = timens_ktime_to_host(timr->it_clock, expires);

kernel/time/posix-timers.h

@@ -42,4 +42,5 @@ void common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting);
 int common_timer_set(struct k_itimer *timr, int flags,
 		     struct itimerspec64 *new_setting,
 		     struct itimerspec64 *old_setting);
+void posix_timer_set_common(struct k_itimer *timer, struct itimerspec64 *new_setting);
 int common_timer_del(struct k_itimer *timer);