1 /*
2 * Generic C implementation of atomic counter operations. Usable on
3 * UP systems only. Do not include in machine independent code.
4 *
5 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public Licence
10 * as published by the Free Software Foundation; either version
11 * 2 of the Licence, or (at your option) any later version.
12 */
13 #ifndef __ASM_GENERIC_ATOMIC_H
14 #define __ASM_GENERIC_ATOMIC_H
15
16 #include <asm/cmpxchg.h>
17 #include <asm/barrier.h>
18
19 /*
20 * atomic_$op() - $op integer to atomic variable
21 * @i: integer value to $op
22 * @v: pointer to the atomic variable
23 *
24 * Atomically $ops @i to @v. Does not strictly guarantee a memory-barrier, use
25 * smp_mb__{before,after}_atomic().
26 */
27
28 /*
29 * atomic_$op_return() - $op interer to atomic variable and returns the result
30 * @i: integer value to $op
31 * @v: pointer to the atomic variable
32 *
33 * Atomically $ops @i to @v. Does imply a full memory barrier.
34 */
35
36 #ifdef CONFIG_SMP
37
38 /* we can build all atomic primitives from cmpxchg */
39
40 #define ATOMIC_OP(op, c_op) \
41 static inline void atomic_##op(int i, atomic_t *v) \
42 { \
43 int c, old; \
44 \
45 c = v->counter; \
46 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
47 c = old; \
48 }
49
50 #define ATOMIC_OP_RETURN(op, c_op) \
51 static inline int atomic_##op##_return(int i, atomic_t *v) \
52 { \
53 int c, old; \
54 \
55 c = v->counter; \
56 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
57 c = old; \
58 \
59 return c c_op i; \
60 }
61
62 #define ATOMIC_FETCH_OP(op, c_op) \
63 static inline int atomic_fetch_##op(int i, atomic_t *v) \
64 { \
65 int c, old; \
66 \
67 c = v->counter; \
68 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
69 c = old; \
70 \
71 return c; \
72 }
73
74 #else
75
76 #include <linux/irqflags.h>
77
78 #define ATOMIC_OP(op, c_op) \
79 static inline void atomic_##op(int i, atomic_t *v) \
80 { \
81 unsigned long flags; \
82 \
83 raw_local_irq_save(flags); \
84 v->counter = v->counter c_op i; \
85 raw_local_irq_restore(flags); \
86 }
87
88 #define ATOMIC_OP_RETURN(op, c_op) \
89 static inline int atomic_##op##_return(int i, atomic_t *v) \
90 { \
91 unsigned long flags; \
92 int ret; \
93 \
94 raw_local_irq_save(flags); \
95 ret = (v->counter = v->counter c_op i); \
96 raw_local_irq_restore(flags); \
97 \
98 return ret; \
99 }
100
101 #define ATOMIC_FETCH_OP(op, c_op) \
102 static inline int atomic_fetch_##op(int i, atomic_t *v) \
103 { \
104 unsigned long flags; \
105 int ret; \
106 \
107 raw_local_irq_save(flags); \
108 ret = v->counter; \
109 v->counter = v->counter c_op i; \
110 raw_local_irq_restore(flags); \
111 \
112 return ret; \
113 }
114
115 #endif /* CONFIG_SMP */
116
117 #ifndef atomic_add_return
118 ATOMIC_OP_RETURN(add, +)
119 #endif
120
121 #ifndef atomic_sub_return
122 ATOMIC_OP_RETURN(sub, -)
123 #endif
124
125 #ifndef atomic_fetch_add
126 ATOMIC_FETCH_OP(add, +)
127 #endif
128
129 #ifndef atomic_fetch_sub
130 ATOMIC_FETCH_OP(sub, -)
131 #endif
132
133 #ifndef atomic_fetch_and
134 ATOMIC_FETCH_OP(and, &)
135 #endif
136
137 #ifndef atomic_fetch_or
138 ATOMIC_FETCH_OP(or, |)
139 #endif
140
141 #ifndef atomic_fetch_xor
142 ATOMIC_FETCH_OP(xor, ^)
143 #endif
144
145 #ifndef atomic_and
146 ATOMIC_OP(and, &)
147 #endif
148
149 #ifndef atomic_or
150 ATOMIC_OP(or, |)
151 #endif
152
153 #ifndef atomic_xor
154 ATOMIC_OP(xor, ^)
155 #endif
156
157 #undef ATOMIC_FETCH_OP
158 #undef ATOMIC_OP_RETURN
159 #undef ATOMIC_OP
160
161 /*
162 * Atomic operations that C can't guarantee us. Useful for
163 * resource counting etc..
164 */
165
166 #define ATOMIC_INIT(i) { (i) }
167
168 /**
169 * atomic_read - read atomic variable
170 * @v: pointer of type atomic_t
171 *
172 * Atomically reads the value of @v.
173 */
174 #ifndef atomic_read
175 #define atomic_read(v) READ_ONCE((v)->counter)
176 #endif
177
178 /**
179 * atomic_set - set atomic variable
180 * @v: pointer of type atomic_t
181 * @i: required value
182 *
183 * Atomically sets the value of @v to @i.
184 */
185 #define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
186
187 #include <linux/irqflags.h>
188
atomic_add(int i,atomic_t * v)189 static inline void atomic_add(int i, atomic_t *v)
190 {
191 atomic_add_return(i, v);
192 }
193
atomic_sub(int i,atomic_t * v)194 static inline void atomic_sub(int i, atomic_t *v)
195 {
196 atomic_sub_return(i, v);
197 }
198
199 #define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
200 #define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
201
202 #endif /* __ASM_GENERIC_ATOMIC_H */
203