1 /* $NetBSD: linux_atomic64.c,v 1.3 2018/08/27 15:11:17 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2018 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Taylor R. Campbell. 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/cdefs.h> 33 __KERNEL_RCSID(0, "$NetBSD: linux_atomic64.c,v 1.3 2018/08/27 15:11:17 riastradh Exp $"); 34 35 #include <sys/param.h> 36 #include <sys/bitops.h> 37 #include <sys/lock.h> 38 39 #include <linux/atomic.h> 40 41 #ifdef __HAVE_ATOMIC64_OPS 42 43 int 44 linux_atomic64_init(void) 45 { 46 return 0; 47 } 48 49 void 50 linux_atomic64_fini(void) 51 { 52 } 53 54 #else 55 56 static struct { 57 kmutex_t lock; 58 uint32_t gen; /* for unlocked read */ 59 char pad[CACHE_LINE_SIZE - 60 sizeof(kmutex_t) - sizeof(uint32_t)]; 61 } atomic64_tab[PAGE_SIZE/CACHE_LINE_SIZE] __cacheline_aligned; 62 CTASSERT(sizeof(atomic64_tab) == PAGE_SIZE); 63 CTASSERT(sizeof(atomic64_tab[0]) == CACHE_LINE_SIZE); 64 65 int 66 linux_atomic64_init(void) 67 { 68 size_t i; 69 70 for (i = 0; i < __arraycount(atomic64_tab); i++) { 71 mutex_init(&atomic64_tab[i].lock, MUTEX_DEFAULT, IPL_HIGH); 72 atomic64_tab[i].gen = 0; 73 } 74 75 return 0; 76 } 77 78 void 79 linux_atomic64_fini(void) 80 { 81 size_t i; 82 83 for (i = 0; i < __arraycount(atomic64_tab); i++) { 84 KASSERT((atomic64_tab[i].gen & 1) == 0); 85 mutex_destroy(&atomic64_tab[i].lock); 86 } 87 } 88 89 static inline size_t 90 atomic64_hash(const struct atomic64 *a) 91 { 92 93 return ((uintptr_t)a >> ilog2(CACHE_LINE_SIZE)) % 94 __arraycount(atomic64_tab); 95 } 96 97 static void 98 atomic64_lock(struct atomic64 *a) 99 { 100 size_t i = atomic64_hash(a); 101 102 mutex_spin_enter(&atomic64_tab[i].lock); 103 KASSERT((atomic64_tab[i].gen & 1) == 0); 104 atomic64_tab[i].gen |= 1; 105 membar_producer(); 106 } 107 108 static void 109 atomic64_unlock(struct atomic64 *a) 110 { 111 size_t i = atomic64_hash(a); 112 113 KASSERT(mutex_owned(&atomic64_tab[i].lock)); 114 KASSERT((atomic64_tab[i].gen & 1) == 1); 115 116 membar_producer(); 117 atomic64_tab[i].gen |= 1; /* paranoia */ 118 atomic64_tab[i].gen++; 119 mutex_spin_exit(&atomic64_tab[i].lock); 120 } 121 122 uint64_t 123 atomic64_read(const struct atomic64 *a) 124 { 125 size_t i = atomic64_hash(a); 126 uint32_t gen; 127 uint64_t value; 128 129 do { 130 while (__predict_false((gen = atomic64_tab[i].gen) & 1)) 131 SPINLOCK_BACKOFF_HOOK; 132 membar_consumer(); 133 value = a->a_v; 134 membar_consumer(); 135 } while (__predict_false(atomic64_tab[i].gen != gen)); 136 137 return value; 138 } 139 140 void 141 atomic64_set(struct atomic64 *a, uint64_t value) 142 { 143 144 atomic64_lock(a); 145 a->a_v = value; 146 atomic64_unlock(a); 147 } 148 149 void 150 atomic64_add(int64_t delta, struct atomic64 *a) 151 { 152 153 atomic64_lock(a); 154 a->a_v += delta; 155 atomic64_unlock(a); 156 } 157 158 void 159 atomic64_sub(int64_t delta, struct atomic64 *a) 160 { 161 162 atomic64_lock(a); 163 a->a_v -= delta; 164 atomic64_unlock(a); 165 } 166 167 int64_t 168 atomic64_add_return(int64_t delta, struct atomic64 *a) 169 { 170 int64_t v; 171 172 atomic64_lock(a); 173 v = (int64_t)(a->a_v += delta); 174 atomic64_unlock(a); 175 176 return v; 177 } 178 179 uint64_t 180 atomic64_xchg(struct atomic64 *a, uint64_t new) 181 { 182 uint64_t old; 183 184 atomic64_lock(a); 185 old = a->a_v; 186 a->a_v = new; 187 atomic64_unlock(a); 188 189 return old; 190 } 191 192 uint64_t 193 atomic64_cmpxchg(struct atomic64 *a, uint64_t expect, uint64_t new) 194 { 195 uint64_t old; 196 197 atomic64_lock(a); 198 old = a->a_v; 199 if (old == expect) 200 a->a_v = new; 201 atomic64_unlock(a); 202 203 return old; 204 } 205 206 #endif 207