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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 */
56 static 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 */
77 static 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
91 static inline int atomic_add_negative(int i, atomic_t *v)
92 {
93 return atomic_add_return(i, v) < 0;
94 }
95
96 static inline void atomic_add(int i, atomic_t *v)
97 {
98 atomic_add_return(i, v);
99 }
100
101 static inline void atomic_sub(int i, atomic_t *v)
102 {
103 atomic_sub_return(i, v);
104 }
105
106 static inline void atomic_inc(atomic_t *v)
107 {
108 atomic_add_return(1, v);
109 }
110
111 static 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
132 static 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
143 static 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 */