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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 * Originally implemented for MN10300.
6 *
7 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
8 * Written by David Howells (dhowells@redhat.com)
9 *
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public Licence
12 * as published by the Free Software Foundation; either version
13 * 2 of the Licence, or (at your option) any later version.
14 */
15#ifndef __ASM_GENERIC_ATOMIC_H
16#define __ASM_GENERIC_ATOMIC_H
17
18#include <asm/cmpxchg.h>
19#include <asm/barrier.h>
20
21#ifdef CONFIG_SMP
22/* Force people to define core atomics */
23# if !defined(atomic_add_return) || !defined(atomic_sub_return) || \
24 !defined(atomic_clear_mask) || !defined(atomic_set_mask)
25# error "SMP requires a little arch-specific magic"
26# endif
27#endif
28
29/*
30 * Atomic operations that C can't guarantee us. Useful for
31 * resource counting etc..
32 */
33
34#define ATOMIC_INIT(i) { (i) }
35
36#ifdef __KERNEL__
37
38/**
39 * atomic_read - read atomic variable
40 * @v: pointer of type atomic_t
41 *
42 * Atomically reads the value of @v.
43 */
44#ifndef atomic_read
45#define atomic_read(v) (*(volatile int *)&(v)->counter)
46#endif
47
48/**
49 * atomic_set - set atomic variable
50 * @v: pointer of type atomic_t
51 * @i: required value
52 *
53 * Atomically sets the value of @v to @i.
54 */
55#define atomic_set(v, i) (((v)->counter) = (i))
56
57#include <linux/irqflags.h>
58
59/**
60 * atomic_add_return - add integer to atomic variable
61 * @i: integer value to add
62 * @v: pointer of type atomic_t
63 *
64 * Atomically adds @i to @v and returns the result
65 */
66#ifndef atomic_add_return
67static inline int atomic_add_return(int i, atomic_t *v)
68{
69 unsigned long flags;
70 int temp;
71
72 raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
73 temp = v->counter;
74 temp += i;
75 v->counter = temp;
76 raw_local_irq_restore(flags);
77
78 return temp;
79}
80#endif
81
82/**
83 * atomic_sub_return - subtract integer from atomic variable
84 * @i: integer value to subtract
85 * @v: pointer of type atomic_t
86 *
87 * Atomically subtracts @i from @v and returns the result
88 */
89#ifndef atomic_sub_return
90static inline int atomic_sub_return(int i, atomic_t *v)
91{
92 unsigned long flags;
93 int temp;
94
95 raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
96 temp = v->counter;
97 temp -= i;
98 v->counter = temp;
99 raw_local_irq_restore(flags);
100
101 return temp;
102}
103#endif
104
105static inline int atomic_add_negative(int i, atomic_t *v)
106{
107 return atomic_add_return(i, v) < 0;
108}
109
110static inline void atomic_add(int i, atomic_t *v)
111{
112 atomic_add_return(i, v);
113}
114
115static inline void atomic_sub(int i, atomic_t *v)
116{
117 atomic_sub_return(i, v);
118}
119
120static inline void atomic_inc(atomic_t *v)
121{
122 atomic_add_return(1, v);
123}
124
125static inline void atomic_dec(atomic_t *v)
126{
127 atomic_sub_return(1, v);
128}
129
130#define atomic_dec_return(v) atomic_sub_return(1, (v))
131#define atomic_inc_return(v) atomic_add_return(1, (v))
132
133#define atomic_sub_and_test(i, v) (atomic_sub_return((i), (v)) == 0)
134#define atomic_dec_and_test(v) (atomic_dec_return(v) == 0)
135#define atomic_inc_and_test(v) (atomic_inc_return(v) == 0)
136
137#define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
138#define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
139
140static inline int __atomic_add_unless(atomic_t *v, int a, int u)
141{
142 int c, old;
143 c = atomic_read(v);
144 while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
145 c = old;
146 return c;
147}
148
149/**
150 * atomic_clear_mask - Atomically clear bits in atomic variable
151 * @mask: Mask of the bits to be cleared
152 * @v: pointer of type atomic_t
153 *
154 * Atomically clears the bits set in @mask from @v
155 */
156#ifndef atomic_clear_mask
157static inline void atomic_clear_mask(unsigned long mask, atomic_t *v)
158{
159 unsigned long flags;
160
161 mask = ~mask;
162 raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
163 v->counter &= mask;
164 raw_local_irq_restore(flags);
165}
166#endif
167
168/**
169 * atomic_set_mask - Atomically set bits in atomic variable
170 * @mask: Mask of the bits to be set
171 * @v: pointer of type atomic_t
172 *
173 * Atomically sets the bits set in @mask in @v
174 */
175#ifndef atomic_set_mask
176static inline void atomic_set_mask(unsigned int mask, atomic_t *v)
177{
178 unsigned long flags;
179
180 raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
181 v->counter |= mask;
182 raw_local_irq_restore(flags);
183}
184#endif
185
186#endif /* __KERNEL__ */
187#endif /* __ASM_GENERIC_ATOMIC_H */