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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) \
41static 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) \
51static 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) \
63static 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) \
79static 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) \
89static 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) \
102static 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
118ATOMIC_OP_RETURN(add, +)
119#endif
120
121#ifndef atomic_sub_return
122ATOMIC_OP_RETURN(sub, -)
123#endif
124
125#ifndef atomic_fetch_add
126ATOMIC_FETCH_OP(add, +)
127#endif
128
129#ifndef atomic_fetch_sub
130ATOMIC_FETCH_OP(sub, -)
131#endif
132
133#ifndef atomic_fetch_and
134ATOMIC_FETCH_OP(and, &)
135#endif
136
137#ifndef atomic_fetch_or
138ATOMIC_FETCH_OP(or, |)
139#endif
140
141#ifndef atomic_fetch_xor
142ATOMIC_FETCH_OP(xor, ^)
143#endif
144
145#ifndef atomic_and
146ATOMIC_OP(and, &)
147#endif
148
149#ifndef atomic_or
150ATOMIC_OP(or, |)
151#endif
152
153#ifndef atomic_xor
154ATOMIC_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
189static inline void atomic_add(int i, atomic_t *v)
190{
191 atomic_add_return(i, v);
192}
193
194static 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 */