2 * Generic C implementation of atomic counter operations. Usable on
3 * UP systems only. Do not include in machine independent code.
5 * Originally implemented for MN10300.
7 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
8 * Written by David Howells (dhowells@redhat.com)
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.
15 #ifndef __ASM_GENERIC_ATOMIC_H
16 #define __ASM_GENERIC_ATOMIC_H
18 #include <asm/cmpxchg.h>
19 #include <asm/barrier.h>
22 * atomic_$op() - $op integer to atomic variable
23 * @i: integer value to $op
24 * @v: pointer to the atomic variable
26 * Atomically $ops @i to @v. Does not strictly guarantee a memory-barrier, use
27 * smp_mb__{before,after}_atomic().
31 * atomic_$op_return() - $op interer to atomic variable and returns the result
32 * @i: integer value to $op
33 * @v: pointer to the atomic variable
35 * Atomically $ops @i to @v. Does imply a full memory barrier.
40 /* we can build all atomic primitives from cmpxchg */
42 #define ATOMIC_OP(op, c_op) \
43 static inline void atomic_##op(int i, atomic_t *v) \
48 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
52 #define ATOMIC_OP_RETURN(op, c_op) \
53 static inline int atomic_##op##_return(int i, atomic_t *v) \
58 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
64 #define ATOMIC_FETCH_OP(op, c_op) \
65 static inline int atomic_fetch_##op(int i, atomic_t *v) \
70 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
78 #include <linux/irqflags.h>
80 #define ATOMIC_OP(op, c_op) \
81 static inline void atomic_##op(int i, atomic_t *v) \
83 unsigned long flags; \
85 raw_local_irq_save(flags); \
86 v->counter = v->counter c_op i; \
87 raw_local_irq_restore(flags); \
90 #define ATOMIC_OP_RETURN(op, c_op) \
91 static inline int atomic_##op##_return(int i, atomic_t *v) \
93 unsigned long flags; \
96 raw_local_irq_save(flags); \
97 ret = (v->counter = v->counter c_op i); \
98 raw_local_irq_restore(flags); \
103 #define ATOMIC_FETCH_OP(op, c_op) \
104 static inline int atomic_fetch_##op(int i, atomic_t *v) \
106 unsigned long flags; \
109 raw_local_irq_save(flags); \
111 v->counter = v->counter c_op i; \
112 raw_local_irq_restore(flags); \
117 #endif /* CONFIG_SMP */
119 #ifndef atomic_add_return
120 ATOMIC_OP_RETURN(add
, +)
123 #ifndef atomic_sub_return
124 ATOMIC_OP_RETURN(sub
, -)
127 #ifndef atomic_fetch_add
128 ATOMIC_FETCH_OP(add
, +)
131 #ifndef atomic_fetch_sub
132 ATOMIC_FETCH_OP(sub
, -)
135 #ifndef atomic_fetch_and
136 ATOMIC_FETCH_OP(and, &)
139 #ifndef atomic_fetch_or
140 ATOMIC_FETCH_OP(or, |)
143 #ifndef atomic_fetch_xor
144 ATOMIC_FETCH_OP(xor, ^)
159 #undef ATOMIC_FETCH_OP
160 #undef ATOMIC_OP_RETURN
164 * Atomic operations that C can't guarantee us. Useful for
165 * resource counting etc..
168 #define ATOMIC_INIT(i) { (i) }
171 * atomic_read - read atomic variable
172 * @v: pointer of type atomic_t
174 * Atomically reads the value of @v.
177 #define atomic_read(v) READ_ONCE((v)->counter)
181 * atomic_set - set atomic variable
182 * @v: pointer of type atomic_t
185 * Atomically sets the value of @v to @i.
187 #define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
189 #include <linux/irqflags.h>
191 static inline int atomic_add_negative(int i
, atomic_t
*v
)
193 return atomic_add_return(i
, v
) < 0;
196 static inline void atomic_add(int i
, atomic_t
*v
)
198 atomic_add_return(i
, v
);
201 static inline void atomic_sub(int i
, atomic_t
*v
)
203 atomic_sub_return(i
, v
);
206 static inline void atomic_inc(atomic_t
*v
)
208 atomic_add_return(1, v
);
211 static inline void atomic_dec(atomic_t
*v
)
213 atomic_sub_return(1, v
);
216 #define atomic_dec_return(v) atomic_sub_return(1, (v))
217 #define atomic_inc_return(v) atomic_add_return(1, (v))
219 #define atomic_sub_and_test(i, v) (atomic_sub_return((i), (v)) == 0)
220 #define atomic_dec_and_test(v) (atomic_dec_return(v) == 0)
221 #define atomic_inc_and_test(v) (atomic_inc_return(v) == 0)
223 #define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
224 #define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
226 static inline int __atomic_add_unless(atomic_t
*v
, int a
, int u
)
230 while (c
!= u
&& (old
= atomic_cmpxchg(v
, c
, c
+ a
)) != c
)
235 #endif /* __ASM_GENERIC_ATOMIC_H */
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