sysdeps/htl/sem-trywait.c

   1 /* Lock a semaphore if it does not require blocking.  Generic version.
   2    Copyright (C) 2005-2018 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library;  if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <semaphore.h>
  20 #include <errno.h>
  21
  22 #include <pt-internal.h>
  23
  24 int
  25 __sem_trywait (sem_t *sem)
  26 {
  27   __pthread_spin_lock (&sem->__lock);
  28   if (sem->__value > 0)
  29     /* Successful down.  */
  30     {
  31       sem->__value--;
  32       __pthread_spin_unlock (&sem->__lock);
  33       return 0;
  34     }
  35   __pthread_spin_unlock (&sem->__lock);
  36
  37   errno = EAGAIN;
  38   return -1;
  39 }
  40
  41 strong_alias (__sem_trywait, sem_trywait);