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
linux_atomic64_init(void)44 linux_atomic64_init(void)
45 {
46 return 0;
47 }
48
49 void
linux_atomic64_fini(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
linux_atomic64_init(void)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
linux_atomic64_fini(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
atomic64_hash(const struct atomic64 * a)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
atomic64_lock(struct atomic64 * a)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
atomic64_unlock(struct atomic64 * a)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
atomic64_read(const struct atomic64 * a)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
atomic64_set(struct atomic64 * a,uint64_t value)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
atomic64_add(int64_t delta,struct atomic64 * a)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
atomic64_sub(int64_t delta,struct atomic64 * a)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
atomic64_add_return(int64_t delta,struct atomic64 * a)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
atomic64_xchg(struct atomic64 * a,uint64_t new)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
atomic64_cmpxchg(struct atomic64 * a,uint64_t expect,uint64_t new)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