sysdeps/htl/pt-once.c

   1 /* pthread_once.  Generic version.
   2    Copyright (C) 2002-2023 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <pthread.h>
  20 #include <atomic.h>
  21
  22 #include <pt-internal.h>
  23
  24 static void
  25 clear_once_control (void *arg)
  26 {
  27   pthread_once_t *once_control = arg;
  28   __pthread_spin_unlock (&once_control->__lock);
  29 }
  30
  31 int
  32 __pthread_once (pthread_once_t *once_control, void (*init_routine) (void))
  33 {
  34   ASSERT_TYPE_SIZE (pthread_once_t, __SIZEOF_PTHREAD_ONCE_T);
  35
  36   atomic_full_barrier ();
  37   if (once_control->__run == 0)
  38     {
  39       __pthread_spin_wait (&once_control->__lock);
  40
  41       if (once_control->__run == 0)
  42         {
  43           pthread_cleanup_push (clear_once_control, once_control);
  44           init_routine ();
  45           pthread_cleanup_pop (0);
  46
  47           atomic_full_barrier ();
  48           once_control->__run = 1;
  49         }
  50
  51       __pthread_spin_unlock (&once_control->__lock);
  52     }
  53
  54   return 0;
  55 }
  56 weak_alias (__pthread_once, pthread_once);