projects/linux·blob v3.2 · refs

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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 ([email protected])
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#ifdef CONFIG_SMP
19/* Force people to define core atomics */
20# if !defined(atomic_add_return) || !defined(atomic_sub_return) || \
21 !defined(atomic_clear_mask) || !defined(atomic_set_mask)
22# error "SMP requires a little arch-specific magic"
23# endif
24#endif
25
26/*
27 * Atomic operations that C can't guarantee us. Useful for
28 * resource counting etc..
29 */
30
31#define ATOMIC_INIT(i) { (i) }
32
33#ifdef __KERNEL__
34
35/**
36 * atomic_read - read atomic variable
37 * @v: pointer of type atomic_t
38 *
39 * Atomically reads the value of @v.
40 */
41#ifndef atomic_read
42#define atomic_read(v) (*(volatile int *)&(v)->counter)
43#endif
44
45/**
46 * atomic_set - set atomic variable
47 * @v: pointer of type atomic_t
48 * @i: required value
49 *
50 * Atomically sets the value of @v to @i.
51 */
52#define atomic_set(v, i) (((v)->counter) = (i))
53
54#include <linux/irqflags.h>
55#include <asm/system.h>
56
57/**
58 * atomic_add_return - add integer to atomic variable
59 * @i: integer value to add
60 * @v: pointer of type atomic_t
61 *
62 * Atomically adds @i to @v and returns the result
63 */
64#ifndef atomic_add_return
65static inline int atomic_add_return(int i, atomic_t *v)
66{
67 unsigned long flags;
68 int temp;
69
70 raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
71 temp = v->counter;
72 temp += i;
73 v->counter = temp;
74 raw_local_irq_restore(flags);
75
76 return temp;
77}
78#endif
79
80/**
81 * atomic_sub_return - subtract integer from atomic variable
82 * @i: integer value to subtract
83 * @v: pointer of type atomic_t
84 *
85 * Atomically subtracts @i from @v and returns the result
86 */
87#ifndef atomic_sub_return
88static inline int atomic_sub_return(int i, atomic_t *v)
89{
90 unsigned long flags;
91 int temp;
92
93 raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
94 temp = v->counter;
95 temp -= i;
96 v->counter = temp;
97 raw_local_irq_restore(flags);
98
99 return temp;
100}
101#endif
102
103static inline int atomic_add_negative(int i, atomic_t *v)
104{
105 return atomic_add_return(i, v) < 0;
106}
107
108static inline void atomic_add(int i, atomic_t *v)
109{
110 atomic_add_return(i, v);
111}
112
113static inline void atomic_sub(int i, atomic_t *v)
114{
115 atomic_sub_return(i, v);
116}
117
118static inline void atomic_inc(atomic_t *v)
119{
120 atomic_add_return(1, v);
121}
122
123static inline void atomic_dec(atomic_t *v)
124{
125 atomic_sub_return(1, v);
126}
127
128#define atomic_dec_return(v) atomic_sub_return(1, (v))
129#define atomic_inc_return(v) atomic_add_return(1, (v))
130
131#define atomic_sub_and_test(i, v) (atomic_sub_return((i), (v)) == 0)
132#define atomic_dec_and_test(v) (atomic_dec_return(v) == 0)
133#define atomic_inc_and_test(v) (atomic_inc_return(v) == 0)
134
135#define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
136#define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
137
138#define cmpxchg_local(ptr, o, n) \
139 ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
140 (unsigned long)(n), sizeof(*(ptr))))
141
142#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
143
144static inline int __atomic_add_unless(atomic_t *v, int a, int u)
145{
146 int c, old;
147 c = atomic_read(v);
148 while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
149 c = old;
150 return c;
151}
152
153/**
154 * atomic_clear_mask - Atomically clear bits in atomic variable
155 * @mask: Mask of the bits to be cleared
156 * @v: pointer of type atomic_t
157 *
158 * Atomically clears the bits set in @mask from @v
159 */
160#ifndef atomic_clear_mask
161static inline void atomic_clear_mask(unsigned long mask, atomic_t *v)
162{
163 unsigned long flags;
164
165 mask = ~mask;
166 raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
167 v->counter &= mask;
168 raw_local_irq_restore(flags);
169}
170#endif
171
172/**
173 * atomic_set_mask - Atomically set bits in atomic variable
174 * @mask: Mask of the bits to be set
175 * @v: pointer of type atomic_t
176 *
177 * Atomically sets the bits set in @mask in @v
178 */
179#ifndef atomic_set_mask
180static inline void atomic_set_mask(unsigned int mask, atomic_t *v)
181{
182 unsigned long flags;
183
184 raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
185 v->counter |= mask;
186 raw_local_irq_restore(flags);
187}
188#endif
189
190/* Assume that atomic operations are already serializing */
191#define smp_mb__before_atomic_dec() barrier()
192#define smp_mb__after_atomic_dec() barrier()
193#define smp_mb__before_atomic_inc() barrier()
194#define smp_mb__after_atomic_inc() barrier()
195
196#endif /* __KERNEL__ */
197#endif /* __ASM_GENERIC_ATOMIC_H */