src/thread/sem_post.c

   1 #include <semaphore.h>
   2 #include <limits.h>
   3 #include "pthread_impl.h"
   4
   5 int sem_post(sem_t *sem)
   6 {
   7         int val, new, waiters, priv = sem->__val[2];
   8         do {
   9                 val = sem->__val[0];
  10                 waiters = sem->__val[1];
  11                 if ((val & SEM_VALUE_MAX) == SEM_VALUE_MAX) {
  12                         errno = EOVERFLOW;
  13                         return -1;
  14                 }
  15                 new = val + 1;
  16                 if (waiters <= 1)
  17                         new &= ~0x80000000;
  18         } while (a_cas(sem->__val, val, new) != val);
  19         if (val<0) __wake(sem->__val, waiters>1 ? 1 : -1, priv);
  20         return 0;
  21 }