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 35 _atomic_lock(volatile _atomic_lock_t *lock) 36 { 37 _atomic_lock_t old = 0; 38 uint32_t scratch = 0; 39 40 __asm__("1: ldaxr %w0, [%x1] \n" 41 " stlxr %w2, %w3, [%x1] \n" 42 " cmp %w2, #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