nptl/sem_getvalue.c

   1 /* Copyright (C) 2002-2018 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   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 <shlib-compat.h>
  21 #include "semaphoreP.h"
  22 #include <atomic.h>
  23
  24
  25 int
  26 __new_sem_getvalue (sem_t *sem, int *sval)
  27 {
  28   struct new_sem *isem = (struct new_sem *) sem;
  29
  30   /* XXX Check for valid SEM parameter.  */
  31   /* FIXME This uses relaxed MO, even though POSIX specifies that this function
  32      should be linearizable.  However, its debatable whether linearizability
  33      is the right requirement.  We need to follow up with POSIX and, if
  34      necessary, use a stronger MO here and elsewhere (e.g., potentially
  35      release MO in all places where we consume a token).  */
  36
  37 #if __HAVE_64B_ATOMICS
  38   *sval = atomic_load_relaxed (&isem->data) & SEM_VALUE_MASK;
  39 #else
  40   *sval = atomic_load_relaxed (&isem->value) >> SEM_VALUE_SHIFT;
  41 #endif
  42
  43   return 0;
  44 }
  45 versioned_symbol (libpthread, __new_sem_getvalue, sem_getvalue, GLIBC_2_1);
  46 #if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_1)
  47 int
  48 __old_sem_getvalue (sem_t *sem, int *sval)
  49 {
  50   struct old_sem *isem = (struct old_sem *) sem;
  51   *sval = isem->value;
  52   return 0;
  53 }
  54 compat_symbol (libpthread, __old_sem_getvalue, sem_getvalue, GLIBC_2_0);
  55 #endif