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1/* Once-only control (native Windows implementation).
2 Copyright (C) 2005-2023 Free Software Foundation, Inc.
3
4 This file is free software: you can redistribute it and/or modify
5 it under the terms of the GNU Lesser General Public License as
6 published by the Free Software Foundation; either version 2.1 of the
7 License, or (at your option) any later version.
8
9 This file 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
12 GNU Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
16
17/* Written by Bruno Haible <bruno@clisp.org>, 2005.
18 Based on GCC's gthr-win32.h. */
19
20#include <config.h>
21
22/* Specification. */
23#include "windows-once.h"
24
25#include <stdlib.h>
26
27void
28glwthread_once (glwthread_once_t *once_control, void (*initfunction) (void))
29{
30 if (once_control->inited <= 0)
31 {
32 if (InterlockedIncrement (&once_control->started) == 0)
33 {
34 /* This thread is the first one to come to this once_control. */
35 InitializeCriticalSection (&once_control->lock);
36 EnterCriticalSection (&once_control->lock);
37 once_control->inited = 0;
38 initfunction ();
39 once_control->inited = 1;
40 LeaveCriticalSection (&once_control->lock);
41 }
42 else
43 {
44 /* Don't let once_control->started grow and wrap around. */
45 InterlockedDecrement (&once_control->started);
46 /* Some other thread has already started the initialization.
47 Yield the CPU while waiting for the other thread to finish
48 initializing and taking the lock. */
49 while (once_control->inited < 0)
50 Sleep (0);
51 if (once_control->inited <= 0)
52 {
53 /* Take the lock. This blocks until the other thread has
54 finished calling the initfunction. */
55 EnterCriticalSection (&once_control->lock);
56 LeaveCriticalSection (&once_control->lock);
57 if (!(once_control->inited > 0))
58 abort ();
59 }
60 }
61 }
62}