simple implementation of POSIX thread barriers

thread_barrier.c

#include <pthread.h>
#include <stdint.h>
#include <stdbool.h>

typedef struct barrier {
  uint32_t threshold;
  uint32_t curr_wait; /* from 0 -> threshold - 1*/
  pthread_cond_t cv;
  pthread_mutex_t mutex; /* perform mutually exclusive ops on a thread barrier */
  bool is_ready; /* is barrier disposition in progress? */
  pthread_cond_t busy_cv; /* thread barrier in disposition progress state, block inbound threads */ 
} barrier_t;

void barrier_init(barrier_t* barrier, uint32_t threshold);

void barrier_wait(barrier_t* barrier);


void barrier_init(barrier_t* barrier, uint32_t threshold) {
  barrier->threshold = threshold;
  barrier->curr_wait = 0;

  pthread_cond_init(&barrier->cv, NULL);
  pthread_mutex_init(&barrier->mutex, NULL);

  barrier->is_ready = true;
  pthread_cond_init(&barrier->busy_cv, NULL);
}

void barrier_wait(barrier_t* barrier) {
  pthread_mutex_lock(&barrier->mutex);

  while (!barrier->is_ready) {
    pthread_cond_wait(&barrier->busy_cv, &barrier->mutex);
  }

  if (barrier->curr_wait + 1 == barrier->threshold) {
    barrier->is_ready = false;
    
    pthread_cond_signal(&barrier->cv);
    pthread_mutex_lock(&barrier->mutex);

    return;
  }

  barrier->curr_wait++;
  pthread_cond_wait(&barrier->cv, &barrier->mutex);
  barrier->curr_wait--;

  if (barrier->curr_wait == 0) {
    barrier->is_ready = true;
    pthread_cond_broadcast(&barrier->cv);
  } else {
    pthread_cond_signal(&barrier->cv);
  }

  pthread_mutex_lock(&barrier->mutex);
}