1 /* $OpenBSD: _atomic_lock.c,v 1.2 2018/05/17 20:28:32 kettenis Exp $ */
2
3 /*
4 * Copyright (c) 2004 Dale Rahn. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 /*
28 * Atomic lock for arm
29 */
30
31 #include <sys/types.h>
32 #include <machine/spinlock.h>
33
34 int
_atomic_lock(volatile _atomic_lock_t * lock)35 _atomic_lock(volatile _atomic_lock_t *lock)
36 {
37 _atomic_lock_t old = 0;
38 uint32_t scratch = 0;
39
40 __asm__("1: ldrex %0, [%1] \n"
41 " strex %2, %3, [%1] \n"
42 " cmp %2, #0 \n"
43 " bne 1b \n"
44 : "+r" (old), "+r" (lock), "+r" (scratch)
45 : "r" (_ATOMIC_LOCK_LOCKED));
46
47 return (old != _ATOMIC_LOCK_UNLOCKED);
48 }
49