nptl/sem_getvalue.c

   1 /* Copyright (C) 2002-2023 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <semaphore.h>
  19 #include <shlib-compat.h>
  20 #include "semaphoreP.h"
  21 #include <atomic.h>
  22
  23
  24 int
  25 __new_sem_getvalue (sem_t *sem, int *sval)
  26 {
  27   struct new_sem *isem = (struct new_sem *) sem;
  28
  29   /* XXX Check for valid SEM parameter.  */
  30   /* FIXME This uses relaxed MO, even though POSIX specifies that this function
  31      should be linearizable.  However, its debatable whether linearizability
  32      is the right requirement.  We need to follow up with POSIX and, if
  33      necessary, use a stronger MO here and elsewhere (e.g., potentially
  34      release MO in all places where we consume a token).  */
  35
  36 #if __HAVE_64B_ATOMICS
  37   *sval = atomic_load_relaxed (&isem->data) & SEM_VALUE_MASK;
  38 #else
  39   *sval = atomic_load_relaxed (&isem->value) >> SEM_VALUE_SHIFT;
  40 #endif
  41
  42   return 0;
  43 }
  44 versioned_symbol (libc, __new_sem_getvalue, sem_getvalue, GLIBC_2_34);
  45
  46 #if OTHER_SHLIB_COMPAT(libpthread, GLIBC_2_1, GLIBC_2_34)
  47 compat_symbol (libpthread, __new_sem_getvalue, sem_getvalue, GLIBC_2_1);
  48 #endif
  49
  50 #if OTHER_SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_1)
  51 int
  52 __old_sem_getvalue (sem_t *sem, int *sval)
  53 {
  54   struct old_sem *isem = (struct old_sem *) sem;
  55   *sval = isem->value;
  56   return 0;
  57 }
  58 compat_symbol (libpthread, __old_sem_getvalue, sem_getvalue, GLIBC_2_0);
  59 #endif