2 * Generic C implementation of atomic counter operations. Usable on
3 * UP systems only. Do not include in machine independent code.
5 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
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.
13 #ifndef __ASM_GENERIC_ATOMIC_H
14 #define __ASM_GENERIC_ATOMIC_H
16 #include <asm/cmpxchg.h>
17 #include <asm/barrier.h>
20 * atomic_$op() - $op integer to atomic variable
21 * @i: integer value to $op
22 * @v: pointer to the atomic variable
24 * Atomically $ops @i to @v. Does not strictly guarantee a memory-barrier, use
25 * smp_mb__{before,after}_atomic().
29 * atomic_$op_return() - $op interer to atomic variable and returns the result
30 * @i: integer value to $op
31 * @v: pointer to the atomic variable
33 * Atomically $ops @i to @v. Does imply a full memory barrier.
38 /* we can build all atomic primitives from cmpxchg */
40 #define ATOMIC_OP(op, c_op) \
41 static inline void atomic_##op(int i, atomic_t *v) \
46 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
50 #define ATOMIC_OP_RETURN(op, c_op) \
51 static inline int atomic_##op##_return(int i, atomic_t *v) \
56 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
62 #define ATOMIC_FETCH_OP(op, c_op) \
63 static inline int atomic_fetch_##op(int i, atomic_t *v) \
68 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
76 #include <linux/irqflags.h>
78 #define ATOMIC_OP(op, c_op) \
79 static inline void atomic_##op(int i, atomic_t *v) \
81 unsigned long flags; \
83 raw_local_irq_save(flags); \
84 v->counter = v->counter c_op i; \
85 raw_local_irq_restore(flags); \
88 #define ATOMIC_OP_RETURN(op, c_op) \
89 static inline int atomic_##op##_return(int i, atomic_t *v) \
91 unsigned long flags; \
94 raw_local_irq_save(flags); \
95 ret = (v->counter = v->counter c_op i); \
96 raw_local_irq_restore(flags); \
101 #define ATOMIC_FETCH_OP(op, c_op) \
102 static inline int atomic_fetch_##op(int i, atomic_t *v) \
104 unsigned long flags; \
107 raw_local_irq_save(flags); \
109 v->counter = v->counter c_op i; \
110 raw_local_irq_restore(flags); \
115 #endif /* CONFIG_SMP */
117 #ifndef atomic_add_return
118 ATOMIC_OP_RETURN(add, +)
121 #ifndef atomic_sub_return
122 ATOMIC_OP_RETURN(sub, -)
125 #ifndef atomic_fetch_add
126 ATOMIC_FETCH_OP(add, +)
129 #ifndef atomic_fetch_sub
130 ATOMIC_FETCH_OP(sub, -)
133 #ifndef atomic_fetch_and
134 ATOMIC_FETCH_OP(and, &)
137 #ifndef atomic_fetch_or
138 ATOMIC_FETCH_OP(or, |)
141 #ifndef atomic_fetch_xor
142 ATOMIC_FETCH_OP(xor, ^)
157 #undef ATOMIC_FETCH_OP
158 #undef ATOMIC_OP_RETURN
162 * Atomic operations that C can't guarantee us. Useful for
163 * resource counting etc..
166 #define ATOMIC_INIT(i) { (i) }
169 * atomic_read - read atomic variable
170 * @v: pointer of type atomic_t
172 * Atomically reads the value of @v.
175 #define atomic_read(v) READ_ONCE((v)->counter)
179 * atomic_set - set atomic variable
180 * @v: pointer of type atomic_t
183 * Atomically sets the value of @v to @i.
185 #define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
187 #include <linux/irqflags.h>
189 static inline void atomic_add(int i, atomic_t *v)
191 atomic_add_return(i, v);
194 static inline void atomic_sub(int i, atomic_t *v)
196 atomic_sub_return(i, v);
199 #define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
200 #define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
202 #endif /* __ASM_GENERIC_ATOMIC_H */