static int ladder_select_state()

in governors/ladder.c [66:125]

• 48 lines of code
• 16 McCabe index (conditional complexity)

static int ladder_select_state(struct cpuidle_driver *drv,
			       struct cpuidle_device *dev, bool *dummy)
{
	struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
	struct ladder_device_state *last_state;
	int last_idx = dev->last_state_idx;
	int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;
	s64 latency_req = cpuidle_governor_latency_req(dev->cpu);
	s64 last_residency;

	/* Special case when user has set very strict latency requirement */
	if (unlikely(latency_req == 0)) {
		ladder_do_selection(dev, ldev, last_idx, 0);
		return 0;
	}

	last_state = &ldev->states[last_idx];

	last_residency = dev->last_residency_ns - drv->states[last_idx].exit_latency_ns;

	/* consider promotion */
	if (last_idx < drv->state_count - 1 &&
	    !dev->states_usage[last_idx + 1].disable &&
	    last_residency > last_state->threshold.promotion_time_ns &&
	    drv->states[last_idx + 1].exit_latency_ns <= latency_req) {
		last_state->stats.promotion_count++;
		last_state->stats.demotion_count = 0;
		if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
			ladder_do_selection(dev, ldev, last_idx, last_idx + 1);
			return last_idx + 1;
		}
	}

	/* consider demotion */
	if (last_idx > first_idx &&
	    (dev->states_usage[last_idx].disable ||
	    drv->states[last_idx].exit_latency_ns > latency_req)) {
		int i;

		for (i = last_idx - 1; i > first_idx; i--) {
			if (drv->states[i].exit_latency_ns <= latency_req)
				break;
		}
		ladder_do_selection(dev, ldev, last_idx, i);
		return i;
	}

	if (last_idx > first_idx &&
	    last_residency < last_state->threshold.demotion_time_ns) {
		last_state->stats.demotion_count++;
		last_state->stats.promotion_count = 0;
		if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {
			ladder_do_selection(dev, ldev, last_idx, last_idx - 1);
			return last_idx - 1;
		}
	}

	/* otherwise remain at the current state */
	return last_idx;
}