1 /* $NetBSD: atomic_cas_by_cas32.c,v 1.3 2014/03/09 16:19:14 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2014 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe. 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 <sys/types.h> 33 #include <sys/inttypes.h> 34 35 uint32_t _atomic_cas_32(volatile uint32_t *addr, uint32_t old, uint32_t new); 36 uint16_t _atomic_cas_16(volatile uint16_t *addr, uint16_t old, uint16_t new); 37 uint8_t _atomic_cas_8(volatile uint8_t *addr, uint8_t old, uint8_t new); 38 39 /* 40 * This file provides emulation of 8 bit and 16 bit CAS operations based on 41 * 32 bit CAS. 42 */ 43 uint16_t 44 _atomic_cas_16(volatile uint16_t *addr, uint16_t old, uint16_t new) 45 { 46 const uintptr_t base = (uintptr_t)addr & ~3; 47 const size_t off = (uintptr_t)addr - base; 48 volatile uint32_t * ptr = (volatile uint32_t *)base; 49 const size_t shift = off*8; 50 const uint32_t mask = 0x0ffff << shift; 51 const uint32_t old32_part = (uint32_t)old << shift; 52 const uint32_t new32_part = (uint32_t)new << shift; 53 uint32_t old32, new32; 54 55 do { 56 old32 = *ptr; 57 if ((old32 & mask) != old32_part) 58 return (uint16_t)((old32 & mask) >> shift); 59 new32 = (old32 & ~mask) | new32_part; 60 } while (_atomic_cas_32(ptr, old32, new32) != old32); 61 62 return old; 63 } 64 65 uint8_t 66 _atomic_cas_8(volatile uint8_t *addr, uint8_t old, uint8_t new) 67 { 68 const uintptr_t base = (uintptr_t)addr & ~3; 69 const size_t off = (uintptr_t)addr - base; 70 volatile uint32_t * ptr = (volatile uint32_t *)base; 71 const size_t shift = off*8; 72 const uint32_t mask = 0x0ff << shift; 73 const uint32_t old32_part = (uint32_t)old << shift; 74 const uint32_t new32_part = (uint32_t)new << shift; 75 uint32_t old32, new32; 76 77 do { 78 old32 = *ptr; 79 if ((old32 & mask) != old32_part) 80 return (uint8_t)((old32 & mask) >> shift); 81 new32 = (old32 & ~mask) | new32_part; 82 } while (_atomic_cas_32(ptr, old32, new32) != old32); 83 84 return old; 85 } 86