zircon/third_party/ulib/musl/pthread/sem_post.c

#include <semaphore.h>

#include "futex_impl.h"
#include "threads_impl.h"

int sem_post(sem_t* sem) {
  int val, waiters;
  do {
    val = atomic_load(&sem->_s_value);
    waiters = atomic_load(&sem->_s_waiters);
    if (val == SEM_VALUE_MAX) {
      errno = EOVERFLOW;
      return -1;
    }
  } while (a_cas_shim(&sem->_s_value, val, val + 1 + (val < 0)) != val);
  if (val < 0 || waiters)
    _zx_futex_wake(&sem->_s_value, 1);
  return 0;
}