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Linux/include/asm-generic/atomic.h

  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 /*
 22  * atomic_$op() - $op integer to atomic variable
 23  * @i: integer value to $op
 24  * @v: pointer to the atomic variable
 25  *
 26  * Atomically $ops @i to @v. Does not strictly guarantee a memory-barrier, use
 27  * smp_mb__{before,after}_atomic().
 28  */
 29 
 30 /*
 31  * atomic_$op_return() - $op interer to atomic variable and returns the result
 32  * @i: integer value to $op
 33  * @v: pointer to the atomic variable
 34  *
 35  * Atomically $ops @i to @v. Does imply a full memory barrier.
 36  */
 37 
 38 #ifdef CONFIG_SMP
 39 
 40 /* we can build all atomic primitives from cmpxchg */
 41 
 42 #define ATOMIC_OP(op, c_op)                                             \
 43 static inline void atomic_##op(int i, atomic_t *v)                      \
 44 {                                                                       \
 45         int c, old;                                                     \
 46                                                                         \
 47         c = v->counter;                                                 \
 48         while ((old = cmpxchg(&v->counter, c, c c_op i)) != c)          \
 49                 c = old;                                                \
 50 }
 51 
 52 #define ATOMIC_OP_RETURN(op, c_op)                                      \
 53 static inline int atomic_##op##_return(int i, atomic_t *v)              \
 54 {                                                                       \
 55         int c, old;                                                     \
 56                                                                         \
 57         c = v->counter;                                                 \
 58         while ((old = cmpxchg(&v->counter, c, c c_op i)) != c)          \
 59                 c = old;                                                \
 60                                                                         \
 61         return c c_op i;                                                \
 62 }
 63 
 64 #else
 65 
 66 #include <linux/irqflags.h>
 67 
 68 #define ATOMIC_OP(op, c_op)                                             \
 69 static inline void atomic_##op(int i, atomic_t *v)                      \
 70 {                                                                       \
 71         unsigned long flags;                                            \
 72                                                                         \
 73         raw_local_irq_save(flags);                                      \
 74         v->counter = v->counter c_op i;                                 \
 75         raw_local_irq_restore(flags);                                   \
 76 }
 77 
 78 #define ATOMIC_OP_RETURN(op, c_op)                                      \
 79 static inline int atomic_##op##_return(int i, atomic_t *v)              \
 80 {                                                                       \
 81         unsigned long flags;                                            \
 82         int ret;                                                        \
 83                                                                         \
 84         raw_local_irq_save(flags);                                      \
 85         ret = (v->counter = v->counter c_op i);                         \
 86         raw_local_irq_restore(flags);                                   \
 87                                                                         \
 88         return ret;                                                     \
 89 }
 90 
 91 #endif /* CONFIG_SMP */
 92 
 93 #ifndef atomic_add_return
 94 ATOMIC_OP_RETURN(add, +)
 95 #endif
 96 
 97 #ifndef atomic_sub_return
 98 ATOMIC_OP_RETURN(sub, -)
 99 #endif
100 
101 #ifndef atomic_clear_mask
102 ATOMIC_OP(and, &)
103 #define atomic_clear_mask(i, v) atomic_and(~(i), (v))
104 #endif
105 
106 #ifndef atomic_set_mask
107 #define CONFIG_ARCH_HAS_ATOMIC_OR
108 ATOMIC_OP(or, |)
109 #define atomic_set_mask(i, v)   atomic_or((i), (v))
110 #endif
111 
112 #undef ATOMIC_OP_RETURN
113 #undef ATOMIC_OP
114 
115 /*
116  * Atomic operations that C can't guarantee us.  Useful for
117  * resource counting etc..
118  */
119 
120 #define ATOMIC_INIT(i)  { (i) }
121 
122 /**
123  * atomic_read - read atomic variable
124  * @v: pointer of type atomic_t
125  *
126  * Atomically reads the value of @v.
127  */
128 #ifndef atomic_read
129 #define atomic_read(v)  ACCESS_ONCE((v)->counter)
130 #endif
131 
132 /**
133  * atomic_set - set atomic variable
134  * @v: pointer of type atomic_t
135  * @i: required value
136  *
137  * Atomically sets the value of @v to @i.
138  */
139 #define atomic_set(v, i) (((v)->counter) = (i))
140 
141 #include <linux/irqflags.h>
142 
143 static inline int atomic_add_negative(int i, atomic_t *v)
144 {
145         return atomic_add_return(i, v) < 0;
146 }
147 
148 static inline void atomic_add(int i, atomic_t *v)
149 {
150         atomic_add_return(i, v);
151 }
152 
153 static inline void atomic_sub(int i, atomic_t *v)
154 {
155         atomic_sub_return(i, v);
156 }
157 
158 static inline void atomic_inc(atomic_t *v)
159 {
160         atomic_add_return(1, v);
161 }
162 
163 static inline void atomic_dec(atomic_t *v)
164 {
165         atomic_sub_return(1, v);
166 }
167 
168 #define atomic_dec_return(v)            atomic_sub_return(1, (v))
169 #define atomic_inc_return(v)            atomic_add_return(1, (v))
170 
171 #define atomic_sub_and_test(i, v)       (atomic_sub_return((i), (v)) == 0)
172 #define atomic_dec_and_test(v)          (atomic_dec_return(v) == 0)
173 #define atomic_inc_and_test(v)          (atomic_inc_return(v) == 0)
174 
175 #define atomic_xchg(ptr, v)             (xchg(&(ptr)->counter, (v)))
176 #define atomic_cmpxchg(v, old, new)     (cmpxchg(&((v)->counter), (old), (new)))
177 
178 static inline int __atomic_add_unless(atomic_t *v, int a, int u)
179 {
180         int c, old;
181         c = atomic_read(v);
182         while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
183                 c = old;
184         return c;
185 }
186 
187 #endif /* __ASM_GENERIC_ATOMIC_H */
188 

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