xref: /openbmc/linux/include/asm-generic/atomic.h (revision e23feb16)
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 
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 
37 /**
38  * atomic_read - read atomic variable
39  * @v: pointer of type atomic_t
40  *
41  * Atomically reads the value of @v.
42  */
43 #ifndef atomic_read
44 #define atomic_read(v)	(*(volatile int *)&(v)->counter)
45 #endif
46 
47 /**
48  * atomic_set - set atomic variable
49  * @v: pointer of type atomic_t
50  * @i: required value
51  *
52  * Atomically sets the value of @v to @i.
53  */
54 #define atomic_set(v, i) (((v)->counter) = (i))
55 
56 #include <linux/irqflags.h>
57 
58 /**
59  * atomic_add_return - add integer to atomic variable
60  * @i: integer value to add
61  * @v: pointer of type atomic_t
62  *
63  * Atomically adds @i to @v and returns the result
64  */
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 
81 /**
82  * atomic_sub_return - subtract integer from atomic variable
83  * @i: integer value to subtract
84  * @v: pointer of type atomic_t
85  *
86  * Atomically subtracts @i from @v and returns the result
87  */
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 static inline int __atomic_add_unless(atomic_t *v, int a, int u)
140 {
141   int c, old;
142   c = atomic_read(v);
143   while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
144     c = old;
145   return c;
146 }
147 
148 /**
149  * atomic_clear_mask - Atomically clear bits in atomic variable
150  * @mask: Mask of the bits to be cleared
151  * @v: pointer of type atomic_t
152  *
153  * Atomically clears the bits set in @mask from @v
154  */
155 #ifndef atomic_clear_mask
156 static inline void atomic_clear_mask(unsigned long mask, atomic_t *v)
157 {
158 	unsigned long flags;
159 
160 	mask = ~mask;
161 	raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
162 	v->counter &= mask;
163 	raw_local_irq_restore(flags);
164 }
165 #endif
166 
167 /**
168  * atomic_set_mask - Atomically set bits in atomic variable
169  * @mask: Mask of the bits to be set
170  * @v: pointer of type atomic_t
171  *
172  * Atomically sets the bits set in @mask in @v
173  */
174 #ifndef atomic_set_mask
175 static inline void atomic_set_mask(unsigned int mask, atomic_t *v)
176 {
177 	unsigned long flags;
178 
179 	raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
180 	v->counter |= mask;
181 	raw_local_irq_restore(flags);
182 }
183 #endif
184 
185 /* Assume that atomic operations are already serializing */
186 #define smp_mb__before_atomic_dec()	barrier()
187 #define smp_mb__after_atomic_dec()	barrier()
188 #define smp_mb__before_atomic_inc()	barrier()
189 #define smp_mb__after_atomic_inc()	barrier()
190 
191 #endif /* __KERNEL__ */
192 #endif /* __ASM_GENERIC_ATOMIC_H */
193