sq_poll.c

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <liburing.h>
#include <string.h>

#define BUF_SIZE    512
#define FILE_NAME1  "/tmp/io_uring_sq_test.txt"
#define STR1        "What is this life if, full of care,\n"
#define STR2        "We have no time to stand and stare."

void print_sq_poll_kernel_thread_status() {

    if (system("ps --ppid 2 | grep io_uring-sq" ) == 0)
        printf("Kernel thread io_uring-sq found running...\n");
    else
        printf("Kernel thread io_uring-sq is not running.\n");
}

int start_fixed_buffer_ops(struct io_uring *ring) {
    int fds[1];
    char buff1[BUF_SIZE];
    char buff2[BUF_SIZE];
    char buff3[BUF_SIZE];
    char buff4[BUF_SIZE];
    struct io_uring_sqe *sqe;
    struct io_uring_cqe *cqe;
    int str1_sz = strlen(STR1);
    int str2_sz = strlen(STR2);

    fds[0] = open(FILE_NAME1, O_RDWR | O_TRUNC | O_CREAT, 0644);
    if (fds[0] < 0 ) {
        perror("open");
        return 1;
    }

    memset(buff1, 0, BUF_SIZE);
    memset(buff2, 0, BUF_SIZE);
    memset(buff3, 0, BUF_SIZE);
    memset(buff4, 0, BUF_SIZE);
    strncpy(buff1, STR1, str1_sz);
    strncpy(buff2, STR2, str2_sz);

    int ret = io_uring_register_files(ring, fds, 1);
    if(ret) {
        fprintf(stderr, "Error registering files: %s", strerror(-ret));
        return 1;
    }

    sqe = io_uring_get_sqe(ring);
    if (!sqe) {
        fprintf(stderr, "Could not get SQE.\n");
        return 1;
    }
    io_uring_prep_write(sqe, 0, buff1, str1_sz, 0);
    io_uring_sqe_set_flags(sqe, IOSQE_FIXED_FILE);

    sqe = io_uring_get_sqe(ring);
    if (!sqe) {
        fprintf(stderr, "Could not get SQE.\n");
        return 1;
    }
    io_uring_prep_write(sqe, 0, buff2, str2_sz, str1_sz);
    io_uring_sqe_set_flags(sqe, IOSQE_FIXED_FILE);

    io_uring_submit(ring);

    for(int i = 0; i < 2; i ++) {
        int ret = io_uring_wait_cqe(ring, &cqe);
        if (ret < 0) {
            fprintf(stderr, "Error waiting for completion: %s\n",
                    strerror(-ret));
            return 1;
        }
        /* Now that we have the CQE, let's process the data */
        if (cqe->res < 0) {
            fprintf(stderr, "Error in async operation: %s\n", strerror(-cqe->res));
        }
        printf("Result of the operation: %d\n", cqe->res);
        io_uring_cqe_seen(ring, cqe);
    }

    print_sq_poll_kernel_thread_status();

    sqe = io_uring_get_sqe(ring);
    if (!sqe) {
        fprintf(stderr, "Could not get SQE.\n");
        return 1;
    }
    io_uring_prep_read(sqe, 0, buff3, str1_sz, 0);
    io_uring_sqe_set_flags(sqe, IOSQE_FIXED_FILE);

    sqe = io_uring_get_sqe(ring);
    if (!sqe) {
        fprintf(stderr, "Could not get SQE.\n");
        return 1;
    }
    io_uring_prep_read(sqe, 0, buff4, str2_sz, str1_sz);
    io_uring_sqe_set_flags(sqe, IOSQE_FIXED_FILE);

    io_uring_submit(ring);

    for(int i = 0; i < 2; i ++) {
        int ret = io_uring_wait_cqe(ring, &cqe);
        if (ret < 0) {
            fprintf(stderr, "Error waiting for completion: %s\n",
                    strerror(-ret));
            return 1;
        }
        /* Now that we have the CQE, let's process the data */
        if (cqe->res < 0) {
            fprintf(stderr, "Error in async operation: %s\n", strerror(-cqe->res));
        }
        printf("Result of the operation: %d\n", cqe->res);
        io_uring_cqe_seen(ring, cqe);
    }
    printf("Contents read from file:\n");
    printf("%s%s", buff3, buff4);
}

int main() {
    struct io_uring ring;
    struct io_uring_params params;

    if (geteuid()) {
        fprintf(stderr, "You need root privileges to run this program.\n");
        return 1;
    }

    print_sq_poll_kernel_thread_status();

    memset(&params, 0, sizeof(params));
    params.flags |= IORING_SETUP_SQPOLL;
    params.sq_thread_idle = 2000;

    int ret = io_uring_queue_init_params(8, &ring, &params);
    if (ret) {
        fprintf(stderr, "Unable to setup io_uring: %s\n", strerror(-ret));
        return 1;
    }
    start_fixed_buffer_ops(&ring);
    io_uring_queue_exit(&ring);
    return 0;
}