1 /*
2  * Generic C implementation of atomic counter operations. Usable on
3  * UP systems only. Do not include in machine independent code.
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 #include <asm/cmpxchg.h>
17 #include <asm/barrier.h>
18 
19 /*
20  * atomic_$op() - $op integer to atomic variable
21  * @i: integer value to $op
22  * @v: pointer to the atomic variable
23  *
24  * Atomically $ops @i to @v. Does not strictly guarantee a memory-barrier, use
25  * smp_mb__{before,after}_atomic().
26  */
27 
28 /*
29  * atomic_$op_return() - $op interer to atomic variable and returns the result
30  * @i: integer value to $op
31  * @v: pointer to the atomic variable
32  *
33  * Atomically $ops @i to @v. Does imply a full memory barrier.
34  */
35 
36 #ifdef CONFIG_SMP
37 
38 /* we can build all atomic primitives from cmpxchg */
39 
40 #define ATOMIC_OP(op, c_op)						\
41 static inline void atomic_##op(int i, atomic_t *v)			\
42 {									\
43 	int c, old;							\
44 									\
45 	c = v->counter;							\
46 	while ((old = cmpxchg(&v->counter, c, c c_op i)) != c)		\
47 		c = old;						\
48 }
49 
50 #define ATOMIC_OP_RETURN(op, c_op)					\
51 static inline int atomic_##op##_return(int i, atomic_t *v)		\
52 {									\
53 	int c, old;							\
54 									\
55 	c = v->counter;							\
56 	while ((old = cmpxchg(&v->counter, c, c c_op i)) != c)		\
57 		c = old;						\
58 									\
59 	return c c_op i;						\
60 }
61 
62 #define ATOMIC_FETCH_OP(op, c_op)					\
63 static inline int atomic_fetch_##op(int i, atomic_t *v)			\
64 {									\
65 	int c, old;							\
66 									\
67 	c = v->counter;							\
68 	while ((old = cmpxchg(&v->counter, c, c c_op i)) != c)		\
69 		c = old;						\
70 									\
71 	return c;							\
72 }
73 
74 #else
75 
76 #include <linux/irqflags.h>
77 
78 #define ATOMIC_OP(op, c_op)						\
79 static inline void atomic_##op(int i, atomic_t *v)			\
80 {									\
81 	unsigned long flags;						\
82 									\
83 	raw_local_irq_save(flags);					\
84 	v->counter = v->counter c_op i;					\
85 	raw_local_irq_restore(flags);					\
86 }
87 
88 #define ATOMIC_OP_RETURN(op, c_op)					\
89 static inline int atomic_##op##_return(int i, atomic_t *v)		\
90 {									\
91 	unsigned long flags;						\
92 	int ret;							\
93 									\
94 	raw_local_irq_save(flags);					\
95 	ret = (v->counter = v->counter c_op i);				\
96 	raw_local_irq_restore(flags);					\
97 									\
98 	return ret;							\
99 }
100 
101 #define ATOMIC_FETCH_OP(op, c_op)					\
102 static inline int atomic_fetch_##op(int i, atomic_t *v)			\
103 {									\
104 	unsigned long flags;						\
105 	int ret;							\
106 									\
107 	raw_local_irq_save(flags);					\
108 	ret = v->counter;						\
109 	v->counter = v->counter c_op i;					\
110 	raw_local_irq_restore(flags);					\
111 									\
112 	return ret;							\
113 }
114 
115 #endif /* CONFIG_SMP */
116 
117 #ifndef atomic_add_return
118 ATOMIC_OP_RETURN(add, +)
119 #endif
120 
121 #ifndef atomic_sub_return
122 ATOMIC_OP_RETURN(sub, -)
123 #endif
124 
125 #ifndef atomic_fetch_add
126 ATOMIC_FETCH_OP(add, +)
127 #endif
128 
129 #ifndef atomic_fetch_sub
130 ATOMIC_FETCH_OP(sub, -)
131 #endif
132 
133 #ifndef atomic_fetch_and
134 ATOMIC_FETCH_OP(and, &)
135 #endif
136 
137 #ifndef atomic_fetch_or
138 ATOMIC_FETCH_OP(or, |)
139 #endif
140 
141 #ifndef atomic_fetch_xor
142 ATOMIC_FETCH_OP(xor, ^)
143 #endif
144 
145 #ifndef atomic_and
146 ATOMIC_OP(and, &)
147 #endif
148 
149 #ifndef atomic_or
150 ATOMIC_OP(or, |)
151 #endif
152 
153 #ifndef atomic_xor
154 ATOMIC_OP(xor, ^)
155 #endif
156 
157 #undef ATOMIC_FETCH_OP
158 #undef ATOMIC_OP_RETURN
159 #undef ATOMIC_OP
160 
161 /*
162  * Atomic operations that C can't guarantee us.  Useful for
163  * resource counting etc..
164  */
165 
166 #define ATOMIC_INIT(i)	{ (i) }
167 
168 /**
169  * atomic_read - read atomic variable
170  * @v: pointer of type atomic_t
171  *
172  * Atomically reads the value of @v.
173  */
174 #ifndef atomic_read
175 #define atomic_read(v)	READ_ONCE((v)->counter)
176 #endif
177 
178 /**
179  * atomic_set - set atomic variable
180  * @v: pointer of type atomic_t
181  * @i: required value
182  *
183  * Atomically sets the value of @v to @i.
184  */
185 #define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
186 
187 #include <linux/irqflags.h>
188 
atomic_add(int i,atomic_t * v)189 static inline void atomic_add(int i, atomic_t *v)
190 {
191 	atomic_add_return(i, v);
192 }
193 
atomic_sub(int i,atomic_t * v)194 static inline void atomic_sub(int i, atomic_t *v)
195 {
196 	atomic_sub_return(i, v);
197 }
198 
199 #define atomic_xchg(ptr, v)		(xchg(&(ptr)->counter, (v)))
200 #define atomic_cmpxchg(v, old, new)	(cmpxchg(&((v)->counter), (old), (new)))
201 
202 #endif /* __ASM_GENERIC_ATOMIC_H */
203