source: example/io/attach-end.c @ 830edc6

/*
This is an example that uses io_uring with attach mode.
It demonstrates the what happens if the original ring is deleted before the other.
It uses liburing for simplicity.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

#include <liburing.h>


char buffer1[1024];
char buffer2[1024];

static void test_read(struct io_uring * ring, int fd) {
        printf("Testing ring %d\n", ring->ring_fd);
        struct io_uring_sqe * sqe = io_uring_get_sqe(ring);
        io_uring_prep_read(sqe, fd, buffer2, 1024, 0);

        io_uring_submit(ring);

        struct io_uring_cqe *cqe;
        int ret = io_uring_wait_cqe(ring, &cqe);
        if( ret < 0) {
                fprintf(stderr, "ioring wait failed: (%d) %s\n", -ret, strerror(-ret));
                exit(EXIT_FAILURE);
        }
        io_uring_cqe_seen(ring, cqe);

        ret = memcmp(buffer1, buffer2, 1024);
        if(ret != 0) {
                fprintf(stderr, "files are different!\n");
                exit(EXIT_FAILURE);
        }
}

int main() {
        const char * path = __FILE__;

        int fd = open(path, 0, O_RDONLY);
        if( fd < 0) {
                fprintf(stderr, "Can't open file: (%d) %s\n", errno, strerror(errno));
                return 1;
        }

        int ret = read(fd, buffer1, 1024);
        if( ret < 0 ) {
                fprintf(stderr, "Can't read file: (%d) %s\n", errno, strerror(errno));
                return 1;
        }

        struct io_uring first_ring;
        io_uring_queue_init(8, &first_ring, 0);
        printf("Created first ring: %d\n", first_ring.ring_fd);

        test_read(&first_ring, fd);


        struct io_uring second_ring;
        struct io_uring_params p;
        memset(&p, '\0', sizeof(struct io_uring_params));
        p.flags |= IORING_SETUP_ATTACH_WQ;
        p.wq_fd = first_ring.ring_fd;
        io_uring_queue_init_params(8, &second_ring, &p);
        printf("Attached second ring: %d\n", second_ring.ring_fd);

        test_read(&second_ring, fd);

        printf("Deleting first ring: %d\n", first_ring.ring_fd);
        io_uring_queue_exit(&first_ring);

        printf("Sleeping (for good measure)\n");

        usleep( 1000000 );

        test_read(&second_ring, fd);

        struct io_uring third_ring;
        memset(&p, '\0', sizeof(struct io_uring_params));
        p.flags |= IORING_SETUP_ATTACH_WQ;
        p.wq_fd = second_ring.ring_fd;
        io_uring_queue_init_params(8, &third_ring, &p);
        printf("Attached third ring: %d\n", third_ring.ring_fd);

        test_read(&third_ring, fd);

        printf("Deleting second ring: %d\n", second_ring.ring_fd);
        io_uring_queue_exit(&second_ring);

        printf("Sleeping (for good measure)\n");

        usleep( 1000000 );

        io_uring_queue_exit(&third_ring);

        close(fd);

        return 0;

}