sysdeps/sparc/sparc32/sem_post.c

   1 /* sem_post -- post to a POSIX semaphore.  Generic futex-using version.
   2    Copyright (C) 2003-2019 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <atomic.h>
  21 #include <errno.h>
  22 #include <sysdep.h>
  23 #include <lowlevellock.h>
  24 #include <internaltypes.h>
  25 #include <semaphore.h>
  26 #include <futex-internal.h>
  27
  28 #include <shlib-compat.h>
  29
  30
  31 /* See sem_wait for an explanation of the algorithm.  */
  32 int
  33 __new_sem_post (sem_t *sem)
  34 {
  35   struct new_sem *isem = (struct new_sem *) sem;
  36   int private = isem->private;
  37   unsigned int v;
  38
  39   __sparc32_atomic_do_lock24 (&isem->pad);
  40
  41   v = isem->value;
  42   if ((v >> SEM_VALUE_SHIFT) == SEM_VALUE_MAX)
  43     {
  44       __sparc32_atomic_do_unlock24 (&isem->pad);
  45
  46       __set_errno (EOVERFLOW);
  47       return -1;
  48     }
  49   isem->value = v + (1 << SEM_VALUE_SHIFT);
  50
  51   __sparc32_atomic_do_unlock24 (&isem->pad);
  52
  53   if ((v & SEM_NWAITERS_MASK) != 0)
  54     futex_wake (&isem->value, 1, private);
  55
  56   return 0;
  57 }
  58 versioned_symbol (libpthread, __new_sem_post, sem_post, GLIBC_2_1);
  59
  60
  61 #if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)
  62 int
  63 attribute_compat_text_section
  64 __old_sem_post (sem_t *sem)
  65 {
  66   int *futex = (int *) sem;
  67
  68   /* We must need to synchronize with consumers of this token, so the atomic
  69      increment must have release MO semantics.  */
  70   atomic_write_barrier ();
  71   (void) atomic_increment_val (futex);
  72   /* We always have to assume it is a shared semaphore.  */
  73   int err = lll_futex_wake (futex, 1, LLL_SHARED);
  74   if (__builtin_expect (err, 0) < 0)
  75     {
  76       __set_errno (-err);
  77       return -1;
  78     }
  79   return 0;
  80 }
  81 compat_symbol (libpthread, __old_sem_post, sem_post, GLIBC_2_0);
  82 #endif