1/* pthread_once. Generic version.
2 Copyright (C) 2002-2022 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
24static void
25clear_once_control (void *arg)
26{
27 pthread_once_t *once_control = arg;
28 __pthread_spin_unlock (&once_control->__lock);
29}
30
31int
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}
56weak_alias (__pthread_once, pthread_once);
57

source code of glibc/sysdeps/htl/pt-once.c