#include <pthread.h>
#include <unistd.h>
#include <assert.h>
#include <stdio.h>

static pthread_mutex_t mutex;

static void *thread(void *arg) {
    printf("[child] lock0\n");
    pthread_mutex_lock(&mutex);
    printf("[child] lock1\n");
    pthread_mutex_lock(&mutex);
    printf("[child] in inner lock!!!\n");
    sleep(3);
    pthread_mutex_unlock(&mutex);
    printf("[child] in outer lock!!!\n");
    pthread_mutex_unlock(&mutex);
    printf("[child] unlocked!!!\n");
    return NULL;
}

int main(int argc, const char **argv) {
    pthread_mutexattr_t mutex_attr;
    pthread_t handle0;

    pthread_mutexattr_init(&mutex_attr);
    pthread_mutexattr_settype(&mutex_attr, PTHREAD_MUTEX_RECURSIVE);
    pthread_mutex_init(&mutex, &mutex_attr);

    pthread_create(&handle0, NULL, thread, "thread0");

    sleep(1);

    pthread_mutex_lock(&mutex);
    printf("[main] inside lock\n");
    sleep(1);
    pthread_mutex_unlock(&mutex);

    pthread_join(handle0, NULL);
    printf("[main] finished\n");

    return 0;
}