1 /* Spin locks (native Windows implementation).
2 Copyright (C) 2019-2020 Free Software Foundation, Inc.
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 3, or (at your option)
7 any later version.
8
9 This program 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 General Public License for more details.
13
14 You should have received a copy of the GNU 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>, 2019. */
18
19 #include <config.h>
20
21 /* Specification. */
22 #include "windows-spin.h"
23
24 #include <errno.h>
25
26 void
glwthread_spin_init(glwthread_spinlock_t * lock)27 glwthread_spin_init (glwthread_spinlock_t *lock)
28 {
29 lock->word = 0;
30 MemoryBarrier ();
31 }
32
33 int
glwthread_spin_lock(glwthread_spinlock_t * lock)34 glwthread_spin_lock (glwthread_spinlock_t *lock)
35 {
36 /* Wait until lock->word becomes 0, then replace it with 1. */
37 /* InterlockedCompareExchange
38 <https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
39 while (InterlockedCompareExchange (&lock->word, 1, 0))
40 ;
41 return 0;
42 }
43
44 int
glwthread_spin_trylock(glwthread_spinlock_t * lock)45 glwthread_spin_trylock (glwthread_spinlock_t *lock)
46 {
47 /* If lock->word is 0, then replace it with 1. */
48 /* InterlockedCompareExchange
49 <https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
50 if (InterlockedCompareExchange (&lock->word, 1, 0))
51 return EBUSY;
52 return 0;
53 }
54
55 int
glwthread_spin_unlock(glwthread_spinlock_t * lock)56 glwthread_spin_unlock (glwthread_spinlock_t *lock)
57 {
58 /* If lock->word is 1, then replace it with 0. */
59 /* InterlockedCompareExchange
60 <https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
61 if (!InterlockedCompareExchange (&lock->word, 0, 1))
62 return EINVAL;
63 return 0;
64 }
65
66 int
glwthread_spin_destroy(glwthread_spinlock_t * lock)67 glwthread_spin_destroy (glwthread_spinlock_t *lock)
68 {
69 return 0;
70 }
71