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atomic.h
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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 #include <asm/cmpxchg.h>
19 
20 #ifdef CONFIG_SMP
21 /* Force people to define core atomics */
22 # if !defined(atomic_add_return) || !defined(atomic_sub_return) || \
23  !defined(atomic_clear_mask) || !defined(atomic_set_mask)
24 # error "SMP requires a little arch-specific magic"
25 # endif
26 #endif
27 
28 /*
29  * Atomic operations that C can't guarantee us. Useful for
30  * resource counting etc..
31  */
32 
33 #define ATOMIC_INIT(i) { (i) }
34 
35 #ifdef __KERNEL__
36 
43 #ifndef atomic_read
44 #define atomic_read(v) (*(volatile int *)&(v)->counter)
45 #endif
46 
54 #define atomic_set(v, i) (((v)->counter) = (i))
55 
56 #include <linux/irqflags.h>
57 
65 #ifndef atomic_add_return
66 static inline int atomic_add_return(int i, atomic_t *v)
67 {
68  unsigned long flags;
69  int temp;
70 
71  raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
72  temp = v->counter;
73  temp += i;
74  v->counter = temp;
75  raw_local_irq_restore(flags);
76 
77  return temp;
78 }
79 #endif
80 
88 #ifndef atomic_sub_return
89 static inline int atomic_sub_return(int i, atomic_t *v)
90 {
91  unsigned long flags;
92  int temp;
93 
94  raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
95  temp = v->counter;
96  temp -= i;
97  v->counter = temp;
98  raw_local_irq_restore(flags);
99 
100  return temp;
101 }
102 #endif
103 
104 static inline int atomic_add_negative(int i, atomic_t *v)
105 {
106  return atomic_add_return(i, v) < 0;
107 }
108 
109 static inline void atomic_add(int i, atomic_t *v)
110 {
111  atomic_add_return(i, v);
112 }
113 
114 static inline void atomic_sub(int i, atomic_t *v)
115 {
116  atomic_sub_return(i, v);
117 }
118 
119 static inline void atomic_inc(atomic_t *v)
120 {
121  atomic_add_return(1, v);
122 }
123 
124 static inline void atomic_dec(atomic_t *v)
125 {
126  atomic_sub_return(1, v);
127 }
128 
129 #define atomic_dec_return(v) atomic_sub_return(1, (v))
130 #define atomic_inc_return(v) atomic_add_return(1, (v))
131 
132 #define atomic_sub_and_test(i, v) (atomic_sub_return((i), (v)) == 0)
133 #define atomic_dec_and_test(v) (atomic_dec_return(v) == 0)
134 #define atomic_inc_and_test(v) (atomic_inc_return(v) == 0)
135 
136 #define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
137 #define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
138 
139 #define cmpxchg_local(ptr, o, n) \
140  ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
141  (unsigned long)(n), sizeof(*(ptr))))
142 
143 #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
144 
145 static inline int __atomic_add_unless(atomic_t *v, int a, int u)
146 {
147  int c, old;
148  c = atomic_read(v);
149  while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
150  c = old;
151  return c;
152 }
153 
161 #ifndef atomic_clear_mask
162 static inline void atomic_clear_mask(unsigned long mask, atomic_t *v)
163 {
164  unsigned long flags;
165 
166  mask = ~mask;
167  raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
168  v->counter &= mask;
169  raw_local_irq_restore(flags);
170 }
171 #endif
172 
180 #ifndef atomic_set_mask
181 static inline void atomic_set_mask(unsigned int mask, atomic_t *v)
182 {
183  unsigned long flags;
184 
185  raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
186  v->counter |= mask;
187  raw_local_irq_restore(flags);
188 }
189 #endif
190 
191 /* Assume that atomic operations are already serializing */
192 #define smp_mb__before_atomic_dec() barrier()
193 #define smp_mb__after_atomic_dec() barrier()
194 #define smp_mb__before_atomic_inc() barrier()
195 #define smp_mb__after_atomic_inc() barrier()
196 
197 #endif /* __KERNEL__ */
198 #endif /* __ASM_GENERIC_ATOMIC_H */