1 /* $NetBSD: atomic_c11_compare_exchange_cas_32.c,v 1.6 2024/01/29 16:09:45 christos Exp $ */
2
3 /*-
4 * Copyright (c) 2007 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Martin Husemann.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #include "atomic_op_namespace.h"
33
34 #if !defined(_KERNEL) && !defined(_STANDALONE)
35 #include <stdbool.h>
36 #endif
37 #include <sys/atomic.h>
38
39 bool __atomic_compare_exchange_4(volatile void *, void *, uint32_t,
40 bool, int, int);
41
42 bool
43 /*ARGSUSED*/
__atomic_compare_exchange_4(volatile void * mem,void * expected,uint32_t desired,bool weak,int success,int failure)44 __atomic_compare_exchange_4(volatile void *mem,
45 void *expected, uint32_t desired,
46 bool weak, int success, int failure)
47 {
48 uint32_t * const ep = expected;
49 const uint32_t old = *ep;
50
51 /*
52 * Ignore the details (weak, memory model on success and failure)
53 * and just do the cas. If we get here the compiler couldn't
54 * do better and it mostly will not matter at all.
55 */
56 const uint32_t prev = atomic_cas_32(mem, old, desired);
57 if (prev == old)
58 return true;
59 *ep = prev;
60 return false;
61 }
62