hrtimer

Linux 6.18.37 LTS: kernel/time/hrtimer.c
Linux 6.18.37 LTS: kernel/time/timer.c
Linux 6.18.37 LTS: include/linux/hrtimer.h

	 * cpu_base->*expires_next is only set by hrtimer_reprogram()
	 */
	hrtimer_reprogram(cpu_base->softirq_next_timer, reprogram);
}

static int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
				    u64 delta_ns, const enum hrtimer_mode mode,
				    struct hrtimer_clock_base *base)
{
	struct hrtimer_clock_base *new_base;
	bool force_local, first;

	/*
	 * If the timer is on the local cpu base and is the first expiring
	 * timer then this might end up reprogramming the hardware twice
	 * (on removal and on enqueue). To avoid that by prevent the
	 * reprogram on removal, keep the timer local to the current CPU
	 * and enforce reprogramming after it is queued no matter whether
	 * it is the new first expiring timer again or not.
	 */
	force_local = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
	force_local &= base->cpu_base->next_timer == timer;

	/*
	 * Remove an active timer from the queue. In case it is not queued
	 * on the current CPU, make sure that remove_hrtimer() updates the
	 * remote data correctly.
	 *
	 * If it's on the current CPU and the first expiring timer, then
	 * skip reprogramming, keep the timer local and enforce
	 * reprogramming later if it was the first expiring timer.  This
	 * avoids programming the underlying clock event twice (once at
	 * removal and once after enqueue).
	 */
	remove_hrtimer(timer, base, true, force_local);

	if (mode & HRTIMER_MODE_REL)
		tim = ktime_add_safe(tim, base->get_time());

	tim = hrtimer_update_lowres(timer, tim, mode);

	WARN_ON_ONCE(base->running != timer);
	base->running = NULL;
}

static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,
				 unsigned long flags, unsigned int active_mask)
{
	struct hrtimer_clock_base *base;
	unsigned int active = cpu_base->active_bases & active_mask;

	for_each_active_base(base, cpu_base, active) {
		struct timerqueue_node *node;
		ktime_t basenow;

		basenow = ktime_add(now, base->offset);

		while ((node = timerqueue_getnext(&base->active))) {
			struct hrtimer *timer;

			timer = container_of(node, struct hrtimer, node);

			/*
			 * The immediate goal for using the softexpires is
			 * minimizing wakeups, not running timers at the
			 * earliest interrupt after their soft expiration.
			 * This allows us to avoid using a Priority Search
			 * Tree, which can answer a stabbing query for
			 * overlapping intervals and instead use the simple
			 * BST we already have.
			 * We don't add extra wakeups by delaying timers that
			 * are right-of a not yet expired timer, because that
			 * timer will have to trigger a wakeup anyway.
			 */
			if (basenow < hrtimer_get_softexpires_tv64(timer))
				break;

			__run_hrtimer(cpu_base, base, timer, &basenow, flags);
			if (active_mask == HRTIMER_ACTIVE_SOFT)
				hrtimer_sync_wait_running(cpu_base, flags);