static int alpha_perf_event_set_period()

in kernel/perf_event.c [252:290]

• 27 lines of code
• 5 McCabe index (conditional complexity)

static int alpha_perf_event_set_period(struct perf_event *event,
				struct hw_perf_event *hwc, int idx)
{
	long left = local64_read(&hwc->period_left);
	long period = hwc->sample_period;
	int ret = 0;

	if (unlikely(left <= -period)) {
		left = period;
		local64_set(&hwc->period_left, left);
		hwc->last_period = period;
		ret = 1;
	}

	if (unlikely(left <= 0)) {
		left += period;
		local64_set(&hwc->period_left, left);
		hwc->last_period = period;
		ret = 1;
	}

	/*
	 * Hardware restrictions require that the counters must not be
	 * written with values that are too close to the maximum period.
	 */
	if (unlikely(left < alpha_pmu->pmc_left[idx]))
		left = alpha_pmu->pmc_left[idx];

	if (left > (long)alpha_pmu->pmc_max_period[idx])
		left = alpha_pmu->pmc_max_period[idx];

	local64_set(&hwc->prev_count, (unsigned long)(-left));

	alpha_write_pmc(idx, (unsigned long)(-left));

	perf_event_update_userpage(event);

	return ret;
}