// https://syzkaller.appspot.com/bug?id=94848148d09f6c10b27d852949f54f9946ab37d0
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
#include <poll.h>
#include <sched.h>

int pipe_fd = -1;
int marker_fd = -1;

void *poll_thread(void *arg) {
    struct pollfd pfd;
    pfd.fd = pipe_fd;
    pfd.events = POLLIN;

    while (1) {
        int res = poll(&pfd, 1, 0);
        if (res < 0) {
            if (errno == EINTR) continue;
            printf("[-] Failed to poll: %s\n", strerror(errno));
            exit(1);
        }
    }
    return NULL;
}

void *write_thread(void *arg) {
    int cpu = (int)(long)arg;
    cpu_set_t cpuset;
    CPU_ZERO(&cpuset);
    
    long num_cpus = sysconf(_SC_NPROCESSORS_ONLN);
    if (num_cpus < 1) num_cpus = 1;
    
    CPU_SET(cpu % num_cpus, &cpuset);
    
    int res = sched_setaffinity(0, sizeof(cpu_set_t), &cpuset);
    if (res < 0) {
        printf("[-] Failed to sched_setaffinity: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] sched_setaffinity successful for CPU %d.\n", cpu);

    while (1) {
        ssize_t wres = write(marker_fd, "a", 1);
        if (wres < 0) {
            printf("[-] Failed to write: %s\n", strerror(errno));
            exit(1);
        }
    }
    return NULL;
}

int main(void) {
    pipe_fd = open("/sys/kernel/tracing/trace_pipe", O_RDONLY);
    if (pipe_fd < 0) {
        pipe_fd = open("/sys/kernel/debug/tracing/trace_pipe", O_RDONLY);
    }
    if (pipe_fd < 0) {
        printf("[-] Failed to open trace_pipe: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] open trace_pipe successful.\n");

    marker_fd = open("/sys/kernel/tracing/trace_marker", O_WRONLY);
    if (marker_fd < 0) {
        marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_WRONLY);
    }
    if (marker_fd < 0) {
        printf("[-] Failed to open trace_marker: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] open trace_marker successful.\n");

    pthread_t p_thread;
    int res = pthread_create(&p_thread, NULL, poll_thread, NULL);
    if (res != 0) {
        printf("[-] Failed to pthread_create poll_thread: %s\n", strerror(res));
        exit(1);
    }
    printf("[+] pthread_create poll_thread successful.\n");

    int num_writers = 2;
    pthread_t w_threads[2];
    for (int i = 0; i < num_writers; i++) {
        res = pthread_create(&w_threads[i], NULL, write_thread, (void *)(long)i);
        if (res != 0) {
            printf("[-] Failed to pthread_create write_thread %d: %s\n", i, strerror(res));
            exit(1);
        }
        printf("[+] pthread_create write_thread %d successful.\n", i);
    }

    // Keep the main thread alive to let the race happen
    while (1) {
        sleep(10);
    }

    return 0;
}