src/thread/sem_trywait.c

   1 #include <semaphore.h>
   2 #include "pthread_impl.h"
   3
   4 int sem_trywait(sem_t *sem)
   5 {
   6         int val;
   7         while ((val=sem->__val[0]) > 0) {
   8                 int new = val-1-(val==1 && sem->__val[1]);
   9                 if (a_cas(sem->__val, val, new)==val) return 0;
  10         }
  11         errno = EAGAIN;
  12         return -1;
  13 }