1 /* $OpenBSD: _atomic_lock.c,v 1.1 2017/08/15 06:13:24 guenther Exp $ */
2 /*
3 * Copyright (c) 2005 Marco Peereboom <marco@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 #include <machine/spinlock.h>
19 #ifdef DIAGNOSTIC
20 #include <stdio.h>
21 #include <stdlib.h>
22 #endif
23
24 int
_atomic_lock(volatile _atomic_lock_t * lock)25 _atomic_lock(volatile _atomic_lock_t *lock)
26 {
27 volatile _atomic_lock_t old;
28
29 #ifdef DIAGNOSTIC
30 if ((unsigned long)lock & 0xf) {
31 printf("lock not 16 byte aligned\n");
32 abort();
33 }
34 #endif
35
36 asm volatile ("ldcws 0(%2),%0"
37 : "=&r" (old), "+m" (lock)
38 : "r" (lock));
39
40 return (old == _ATOMIC_LOCK_LOCKED);
41 }
42