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
atomic_add_return(int i,atomic_t * v)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
atomic_sub_return(int i,atomic_t * v)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
atomic_add_negative(int i,atomic_t * v)104 static inline int atomic_add_negative(int i, atomic_t *v)
105 {
106 return atomic_add_return(i, v) < 0;
107 }
108
atomic_add(int i,atomic_t * v)109 static inline void atomic_add(int i, atomic_t *v)
110 {
111 atomic_add_return(i, v);
112 }
113
atomic_sub(int i,atomic_t * v)114 static inline void atomic_sub(int i, atomic_t *v)
115 {
116 atomic_sub_return(i, v);
117 }
118
atomic_inc(atomic_t * v)119 static inline void atomic_inc(atomic_t *v)
120 {
121 atomic_add_return(1, v);
122 }
123
atomic_dec(atomic_t * v)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
__atomic_add_unless(atomic_t * v,int a,int u)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
atomic_clear_mask(unsigned long mask,atomic_t * v)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
atomic_set_mask(unsigned int mask,atomic_t * v)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