/*

 * Check if the kernel sets IORING_SQ_CQ_OVERFLOW so that peeking events

 * still enter the kernel to flush events, if the CQ side is overflown.

 */

#include <stdio.h>

#include <string.h>

#include <assert.h>

#include "liburing.h"

static int test_cq_overflow(struct io_uring *ring)

{

	struct io_uring_cqe *cqe;

	struct io_uring_sqe *sqe;

	unsigned flags;

	int issued = 0;

	int ret = 0;

	do {

		sqe = io_uring_get_sqe(ring);

		if (!sqe) {

			fprintf(stderr, "get sqe failed\n");

			goto err;

		}

		ret = io_uring_submit(ring);

		if (ret <= 0) {

			if (ret != -EBUSY)

				fprintf(stderr, "sqe submit failed: %d\n", ret);

			break;

		}

		issued++;

	} while (ret > 0);

	assert(ret == -EBUSY);

	flags = IO_URING_READ_ONCE(*ring->sq.kflags);

	if (!(flags & IORING_SQ_CQ_OVERFLOW)) {

		fprintf(stdout, "OVERFLOW not set on -EBUSY, skipping\n");

		goto done;

	}

	while (issued) {

		ret = io_uring_peek_cqe(ring, &cqe);

		if (ret) {

			if (ret != -EAGAIN) {

				fprintf(stderr, "peek completion failed: %s\n",

					strerror(ret));

				break;

			}

			continue;

		}

		io_uring_cqe_seen(ring, cqe);

		issued--;

	}

done:

	return 0;

err:

	return 1;

}

int main(int argc, char *argv[])

{

	int ret;

	struct io_uring ring;

	if (argc > 1)

		return 0;

	ret = io_uring_queue_init(16, &ring, 0);

	if (ret) {

		fprintf(stderr, "ring setup failed: %d\n", ret);

		return 1;

	}

	ret = test_cq_overflow(&ring);

	if (ret) {

		fprintf(stderr, "test_cq_overflow failed\n");

		return 1;

	}

	return 0;

}