genirq/timings: Fix next event index function

static int irq_timings_next_event_index(int *buffer, size_t len, int period_max)

{

	int i;

	int period;

	/*

	 * Move the beginning pointer to the end minus the max period x 3.

	 * We are at the point we can begin searching the pattern

	 */

	buffer = &buffer[len - (period_max * 3)];

	/* Adjust the length to the maximum allowed period x 3 */

	len = period_max * 3;

	/*

	 * The buffer contains the suite of intervals, in a ilog2

	 * period beginning at the end of the buffer. We do that for

	 * each suffix.

	 */

	for (i = period_max; i >= PREDICTION_PERIOD_MIN ; i--) {

	for (period = period_max; period >= PREDICTION_PERIOD_MIN; period--) {

		int *begin = &buffer[len - (i * 3)];

		int *ptr = begin;

		/*

		 * The first comparison always succeed because the

		 * suffix is deduced from the first n-period bytes of

		 * the buffer and we compare the initial suffix with

		 * itself, so we can skip the first iteration.

		 */

		int idx = period;

		size_t size = period;

		/*

		 * We look if the suite with period 'i' repeat

		 * itself. If it is truncated at the end, as it

		 * repeats we can use the period to find out the next

		 * element.

		 * element with the modulo.

		 */

		while (!memcmp(buffer, &buffer[idx], size * sizeof(int))) {

			/*

			 * Move the index in a period basis

			 */

			idx += size;

			/*

			 * If this condition is reached, all previous

			 * memcmp were successful, so the period is

			 * found.

			 */

			if (idx == len)

				return buffer[len % period];

			/*

			 * If the remaining elements to compare are

			 * smaller than the period, readjust the size

			 * of the comparison for the last iteration.

			 */

		while (!memcmp(ptr, begin, i * sizeof(*ptr))) {

			ptr += i;

			if (ptr >= &buffer[len])

				return begin[((i * 3) % i)];

			if (len - idx < period)

				size = len - idx;

		}

	}