// https://syzkaller.appspot.com/bug?id=42c3998fce1a032008cec46ed09481c3f8fc0e84
#define _GNU_SOURCE
#include <fcntl.h>
#include <pthread.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

volatile int stop = 0;

static void *thread1(void *arg)
{
    while (!__atomic_load_n(&stop, __ATOMIC_RELAXED)) {
        int fd = open("test_fifo", O_RDONLY);
        if (fd >= 0) {
            if (close(fd) < 0) {
                // Ignore close errors in threads to avoid spamming
            }
        }
    }
    return NULL;
}

static void *thread2(void *arg)
{
    while (!__atomic_load_n(&stop, __ATOMIC_RELAXED)) {
        int fd = open("test_fifo", O_RDONLY | O_NONBLOCK);
        if (fd >= 0) {
            if (close(fd) < 0) {
                // Ignore close errors in threads
            }
        }
    }
    return NULL;
}

int main(void)
{
    int res;

    // Clean up any existing fifo
    unlink("test_fifo");

    res = mkfifo("test_fifo", 0666);
    if (res < 0) {
        printf("[-] Failed to mkfifo: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] mkfifo successful.\n");

    pthread_t t1[4], t2[4];
    
    for (int i = 0; i < 4; i++) {
        res = pthread_create(&t1[i], NULL, thread1, NULL);
        if (res != 0) {
            printf("[-] Failed to pthread_create thread1: %s\n", strerror(res));
            exit(1);
        }
        res = pthread_create(&t2[i], NULL, thread2, NULL);
        if (res != 0) {
            printf("[-] Failed to pthread_create thread2: %s\n", strerror(res));
            exit(1);
        }
    }
    printf("[+] Threads created successfully.\n");

    // Let the threads race for a few seconds to trigger KCSAN
    sleep(5);
    printf("[+] Sleep finished, stopping threads.\n");

    __atomic_store_n(&stop, 1, __ATOMIC_RELAXED);

    // Wake up blocked readers and keep writer open so new readers don't block
    int wfd = open("test_fifo", O_RDWR);
    if (wfd < 0) {
        printf("[-] Failed to open test_fifo with O_RDWR: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] open test_fifo with O_RDWR successful.\n");

    for (int i = 0; i < 4; i++) {
        res = pthread_join(t1[i], NULL);
        if (res != 0) {
            printf("[-] Failed to pthread_join thread1: %s\n", strerror(res));
            exit(1);
        }
        res = pthread_join(t2[i], NULL);
        if (res != 0) {
            printf("[-] Failed to pthread_join thread2: %s\n", strerror(res));
            exit(1);
        }
    }
    printf("[+] Threads joined successfully.\n");

    res = close(wfd);
    if (res < 0) {
        printf("[-] Failed to close wfd: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] close wfd successful.\n");

    res = unlink("test_fifo");
    if (res < 0) {
        printf("[-] Failed to unlink test_fifo: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] unlink test_fifo successful.\n");

    // Allow time for KCSAN to report
    sleep(1);
    printf("[+] Reproducer finished.\n");

    return 0;
}