Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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
66static 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
89static 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
104static inline int atomic_add_negative(int i, atomic_t *v)
105{
106 return atomic_add_return(i, v) < 0;
107}
108
109static inline void atomic_add(int i, atomic_t *v)
110{
111 atomic_add_return(i, v);
112}
113
114static inline void atomic_sub(int i, atomic_t *v)
115{
116 atomic_sub_return(i, v);
117}
118
119static inline void atomic_inc(atomic_t *v)
120{
121 atomic_add_return(1, v);
122}
123
124static 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
139static 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
156static 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
175static 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 */