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

static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
static int ready = 0;

static void *producer(void *arg)
{ (void)arg;
    pthread_mutex_lock(&mtx);
    ready = 1;
    pthread_mutex_unlock(&mtx);
    return NULL;
}

static void *consumer(void *arg)
{ (void)arg;
    pthread_mutex_lock(&mtx);
    if (ready) {
        /* safe access under lock */
    }
    pthread_mutex_unlock(&mtx);
    return NULL;
}

int main(void)
{
    pthread_t tprod, tcons;
    pthread_create(&tprod, NULL, producer, NULL);
    pthread_create(&tcons, NULL, consumer, NULL);
    pthread_join(tprod, NULL);
    pthread_join(tcons, NULL);
    printf("Concurrency demo finished successfully.\n");
    return 0;
}