int nds32_pmu_event_set_period()

in kernel/perf_event_cpu.c [183:223]

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

int nds32_pmu_event_set_period(struct perf_event *event)
{
	struct nds32_pmu *nds32_pmu = to_nds32_pmu(event->pmu);
	struct hw_perf_event *hwc = &event->hw;
	s64 left = local64_read(&hwc->period_left);
	s64 period = hwc->sample_period;
	int ret = 0;

	/* The period may have been changed by PERF_EVENT_IOC_PERIOD */
	if (unlikely(period != hwc->last_period))
		left = period - (hwc->last_period - left);

	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;
	}

	if (left > (s64)nds32_pmu->max_period)
		left = nds32_pmu->max_period;

	/*
	 * The hw event starts counting from this event offset,
	 * mark it to be able to extract future "deltas":
	 */
	local64_set(&hwc->prev_count, (u64)(-left));

	nds32_pmu->write_counter(event, (u64)(-left) & nds32_pmu->max_period);

	perf_event_update_userpage(event);

	return ret;
}