SO lab7 ex2

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <errno.h>
#include <semaphore.h>
pthread_mutex_t mtx;
sem_t sem;
int n = 5, count;

typedef struct thread
{
    pthread_t thr;
    int id;
}thread;

struct thread th[5];

void barrier_point()
{

    pthread_mutex_lock(&mtx);
    count++;
    pthread_mutex_unlock(&mtx);

    if(count < n)
    {
        sem_wait(&sem);
    }
    else
    {
        for(int i = 0; i < n; i++) sem_post(&sem);
    }
}

void* tfun(void* v)
{
    int id = *(int*) v;

    printf("%d reached the barrier\n", id);
    barrier_point();
    printf("%d passed the barrier\n", id);

    return NULL;
}

int main()
{
    if(pthread_mutex_init(&mtx,NULL))
    {
        perror(NULL);
        return errno;
    }

    if(sem_init(&sem, 0, 0))
    {
        perror(NULL);
        return errno;
    }
    for(int i = 0; i < n; i++)
    {
        th[i].id = i;
        pthread_create(&th[i].thr, NULL, tfun, &th[i].id);
    }

    for(int i = 0; i < n; i++) pthread_join(th[i].thr, NULL);

    pthread_mutex_destroy(&mtx);
    sem_destroy(&sem);

    return 0;
}