libgomp/config/posix/sem.c

   1 /* Copyright (C) 2005-2018 Free Software Foundation, Inc.
   2    Contributed by Richard Henderson <rth@redhat.com>.
   3
   4    This file is part of the GNU Offloading and Multi Processing Library
   5    (libgomp).
   6
   7    Libgomp is free software; you can redistribute it and/or modify it
   8    under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3, or (at your option)
  10    any later version.
  11
  12    Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
  13    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  14    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  15    more details.
  16
  17    Under Section 7 of GPL version 3, you are granted additional
  18    permissions described in the GCC Runtime Library Exception, version
  19    3.1, as published by the Free Software Foundation.
  20
  21    You should have received a copy of the GNU General Public License and
  22    a copy of the GCC Runtime Library Exception along with this program;
  23    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24    <http://www.gnu.org/licenses/>.  */
  25
  26 /* This is the default POSIX 1003.1b implementation of a semaphore
  27    synchronization mechanism for libgomp.  This type is private to
  28    the library.
  29
  30    This is a bit heavy weight for what we need, in that we're not
  31    interested in sem_wait as a cancelation point, but it's not too
  32    bad for a default.  */
  33
  34 #include "libgomp.h"
  35
  36 #ifdef HAVE_BROKEN_POSIX_SEMAPHORES
  37 #include <stdlib.h>
  38
  39 void gomp_sem_init (gomp_sem_t *sem, int value)
  40 {
  41   int ret;
  42
  43   ret = pthread_mutex_init (&sem->mutex, NULL);
  44   if (ret)
  45     return;
  46
  47   ret = pthread_cond_init (&sem->cond, NULL);
  48   if (ret)
  49     return;
  50
  51   sem->value = value;
  52 }
  53
  54 void gomp_sem_wait (gomp_sem_t *sem)
  55 {
  56   int ret;
  57
  58   ret = pthread_mutex_lock (&sem->mutex);
  59   if (ret)
  60     return;
  61
  62   if (sem->value > 0)
  63     {
  64       sem->value--;
  65       ret = pthread_mutex_unlock (&sem->mutex);
  66       return;
  67     }
  68
  69   while (sem->value <= 0)
  70     {
  71       ret = pthread_cond_wait (&sem->cond, &sem->mutex);
  72       if (ret)
  73         {
  74           pthread_mutex_unlock (&sem->mutex);
  75           return;
  76         }
  77     }
  78
  79   sem->value--;
  80   ret = pthread_mutex_unlock (&sem->mutex);
  81   return;
  82 }
  83
  84 void gomp_sem_post (gomp_sem_t *sem)
  85 {
  86   int ret;
  87
  88   ret = pthread_mutex_lock (&sem->mutex);
  89   if (ret)
  90     return;
  91
  92   sem->value++;
  93
  94   ret = pthread_mutex_unlock (&sem->mutex);
  95   if (ret)
  96     return;
  97
  98   ret = pthread_cond_signal (&sem->cond);
  99
 100   return;
 101 }
 102
 103 void gomp_sem_destroy (gomp_sem_t *sem)
 104 {
 105   int ret;
 106
 107   ret = pthread_mutex_destroy (&sem->mutex);
 108   if (ret)
 109     return;
 110
 111   ret = pthread_cond_destroy (&sem->cond);
 112
 113   return;
 114 }
 115 #else /* HAVE_BROKEN_POSIX_SEMAPHORES  */
 116 void
 117 gomp_sem_wait (gomp_sem_t *sem)
 118 {
 119   /* With POSIX, the wait can be canceled by signals.  We don't want that.
 120      It is expected that the return value here is -1 and errno is EINTR.  */
 121   while (sem_wait (sem) != 0)
 122     continue;
 123 }
 124 #endif