Root/include/asm-generic/atomic.h

1/*
2 * Generic C implementation of atomic counter operations
3 * Originally implemented for MN10300.
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#ifdef CONFIG_SMP
17#error not SMP safe
18#endif
19
20/*
21 * Atomic operations that C can't guarantee us. Useful for
22 * resource counting etc..
23 */
24
25#define ATOMIC_INIT(i) { (i) }
26
27#ifdef __KERNEL__
28
29/**
30 * atomic_read - read atomic variable
31 * @v: pointer of type atomic_t
32 *
33 * Atomically reads the value of @v.
34 */
35#define atomic_read(v) (*(volatile int *)&(v)->counter)
36
37/**
38 * atomic_set - set atomic variable
39 * @v: pointer of type atomic_t
40 * @i: required value
41 *
42 * Atomically sets the value of @v to @i.
43 */
44#define atomic_set(v, i) (((v)->counter) = (i))
45
46#include <linux/irqflags.h>
47#include <asm/system.h>
48
49/**
50 * atomic_add_return - add integer to atomic variable
51 * @i: integer value to add
52 * @v: pointer of type atomic_t
53 *
54 * Atomically adds @i to @v and returns the result
55 */
56static inline int atomic_add_return(int i, atomic_t *v)
57{
58    unsigned long flags;
59    int temp;
60
61    raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
62    temp = v->counter;
63    temp += i;
64    v->counter = temp;
65    raw_local_irq_restore(flags);
66
67    return temp;
68}
69
70/**
71 * atomic_sub_return - subtract integer from atomic variable
72 * @i: integer value to subtract
73 * @v: pointer of type atomic_t
74 *
75 * Atomically subtracts @i from @v and returns the result
76 */
77static inline int atomic_sub_return(int i, atomic_t *v)
78{
79    unsigned long flags;
80    int temp;
81
82    raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
83    temp = v->counter;
84    temp -= i;
85    v->counter = temp;
86    raw_local_irq_restore(flags);
87
88    return temp;
89}
90
91static inline int atomic_add_negative(int i, atomic_t *v)
92{
93    return atomic_add_return(i, v) < 0;
94}
95
96static inline void atomic_add(int i, atomic_t *v)
97{
98    atomic_add_return(i, v);
99}
100
101static inline void atomic_sub(int i, atomic_t *v)
102{
103    atomic_sub_return(i, v);
104}
105
106static inline void atomic_inc(atomic_t *v)
107{
108    atomic_add_return(1, v);
109}
110
111static inline void atomic_dec(atomic_t *v)
112{
113    atomic_sub_return(1, v);
114}
115
116#define atomic_dec_return(v) atomic_sub_return(1, (v))
117#define atomic_inc_return(v) atomic_add_return(1, (v))
118
119#define atomic_sub_and_test(i, v) (atomic_sub_return((i), (v)) == 0)
120#define atomic_dec_and_test(v) (atomic_sub_return(1, (v)) == 0)
121#define atomic_inc_and_test(v) (atomic_add_return(1, (v)) == 0)
122
123#define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
124#define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
125
126#define cmpxchg_local(ptr, o, n) \
127    ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
128            (unsigned long)(n), sizeof(*(ptr))))
129
130#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
131
132static inline int atomic_add_unless(atomic_t *v, int a, int u)
133{
134  int c, old;
135  c = atomic_read(v);
136  while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
137    c = old;
138  return c != u;
139}
140
141#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
142
143static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
144{
145    unsigned long flags;
146
147    mask = ~mask;
148    raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
149    *addr &= mask;
150    raw_local_irq_restore(flags);
151}
152
153/* Assume that atomic operations are already serializing */
154#define smp_mb__before_atomic_dec() barrier()
155#define smp_mb__after_atomic_dec() barrier()
156#define smp_mb__before_atomic_inc() barrier()
157#define smp_mb__after_atomic_inc() barrier()
158
159#include <asm-generic/atomic-long.h>
160
161#endif /* __KERNEL__ */
162#endif /* __ASM_GENERIC_ATOMIC_H */
163

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