Quelle  pthread_barrier_wait.c

/*-------------------------------------------------------------------------
 *
 * pthread_barrier_wait.c
 *    Implementation of pthread_barrier_t support for platforms lacking it.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/port/pthread_barrier_wait.c
 *
 *-------------------------------------------------------------------------
 */

#include "c.h"

#include "port/pg_pthread.h"

int
pthread_barrier_init(pthread_barrier_t *barrier, const void *attr, int count)
{
 int   error;

 barrier->sense = false;
 barrier->count = count;
 barrier->arrived = 0;
 if ((error = pthread_cond_init(&barrier->cond, NULL)) != 0)
  return error;
 if ((error = pthread_mutex_init(&barrier->mutex, NULL)) != 0)
 {
  pthread_cond_destroy(&barrier->cond);
  return error;
 }

 return 0;
}

int
pthread_barrier_wait(pthread_barrier_t *barrier)
{
 bool  initial_sense;

 pthread_mutex_lock(&barrier->mutex);

 /* We have arrived at the barrier. */
 barrier->arrived++;
 Assert(barrier->arrived <= barrier->count);

 /* If we were the last to arrive, release the others and return. */
 if (barrier->arrived == barrier->count)
 {
  barrier->arrived = 0;
  barrier->sense = !barrier->sense;
  pthread_mutex_unlock(&barrier->mutex);
  pthread_cond_broadcast(&barrier->cond);

  return PTHREAD_BARRIER_SERIAL_THREAD;
 }

 /* Wait for someone else to flip the sense. */
 initial_sense = barrier->sense;
 do
 {
  pthread_cond_wait(&barrier->cond, &barrier->mutex);
 } while (barrier->sense == initial_sense);

 pthread_mutex_unlock(&barrier->mutex);

 return 0;
}

int
pthread_barrier_destroy(pthread_barrier_t *barrier)
{
 pthread_cond_destroy(&barrier->cond);
 pthread_mutex_destroy(&barrier->mutex);
 return 0;
}