barrier.c

/**
* Luscious Locks Lab
* CS 241 - Fall 2016
*/
#include "barrier.h"

// The returns are just for errors if you want to check for them.
int barrier_destroy(barrier_t *barrier) {
	int error = 0;
	error += pthread_mutex_destroy(&(barrier -> mtx));
	error += pthread_cond_destroy(&(barrier -> cv));
	return error;
}

int barrier_init(barrier_t *barrier, unsigned int num_threads) {
	int error = 0;
	barrier -> n_threads = num_threads;
	barrier -> count = 0;
	barrier -> times_used = 0;
	error += pthread_mutex_init(&(barrier -> mtx), NULL);
	error += pthread_cond_init(&(barrier -> cv), NULL);
	return error;
}

int barrier_wait(barrier_t *barrier) {
	pthread_mutex_lock(&barrier -> mtx);
	barrier -> count++;
	unsigned int previous = barrier -> times_used;
	if(barrier -> count == barrier -> n_threads){
		pthread_cond_broadcast(&barrier -> cv);
		barrier -> count = 0;
		barrier -> times_used++;
	}
	else{
		while(barrier -> count < barrier -> n_threads && barrier -> times_used == previous){
			pthread_cond_wait(&barrier -> cv, &barrier -> mtx);
		}
	}
	pthread_mutex_unlock(&barrier -> mtx);
	return 0;
}