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 /* Force people to define core atomics */
23 # if !defined(atomic_add_return) || !defined(atomic_sub_return) || \
24 !defined(atomic_clear_mask) || !defined(atomic_set_mask)
25 # error "SMP requires a little arch-specific magic"
30 * Atomic operations that C can't guarantee us. Useful for
31 * resource counting etc..
34 #define ATOMIC_INIT(i) { (i) }
39 * atomic_read - read atomic variable
40 * @v: pointer of type atomic_t
42 * Atomically reads the value of @v.
45 #define atomic_read(v) (*(volatile int *)&(v)->counter)
49 * atomic_set - set atomic variable
50 * @v: pointer of type atomic_t
53 * Atomically sets the value of @v to @i.
55 #define atomic_set(v, i) (((v)->counter) = (i))
57 #include <linux/irqflags.h>
60 * atomic_add_return - add integer to atomic variable
61 * @i: integer value to add
62 * @v: pointer of type atomic_t
64 * Atomically adds @i to @v and returns the result
66 #ifndef atomic_add_return
67 static inline int atomic_add_return(int i, atomic_t *v)
72 raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
76 raw_local_irq_restore(flags);
83 * atomic_sub_return - subtract integer from atomic variable
84 * @i: integer value to subtract
85 * @v: pointer of type atomic_t
87 * Atomically subtracts @i from @v and returns the result
89 #ifndef atomic_sub_return
90 static inline int atomic_sub_return(int i, atomic_t *v)
95 raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
99 raw_local_irq_restore(flags);
105 static inline int atomic_add_negative(int i, atomic_t *v)
107 return atomic_add_return(i, v) < 0;
110 static inline void atomic_add(int i, atomic_t *v)
112 atomic_add_return(i, v);
115 static inline void atomic_sub(int i, atomic_t *v)
117 atomic_sub_return(i, v);
120 static inline void atomic_inc(atomic_t *v)
122 atomic_add_return(1, v);
125 static inline void atomic_dec(atomic_t *v)
127 atomic_sub_return(1, v);
130 #define atomic_dec_return(v) atomic_sub_return(1, (v))
131 #define atomic_inc_return(v) atomic_add_return(1, (v))
133 #define atomic_sub_and_test(i, v) (atomic_sub_return((i), (v)) == 0)
134 #define atomic_dec_and_test(v) (atomic_dec_return(v) == 0)
135 #define atomic_inc_and_test(v) (atomic_inc_return(v) == 0)
137 #define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
138 #define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
140 static inline int __atomic_add_unless(atomic_t *v, int a, int u)
144 while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
150 * atomic_clear_mask - Atomically clear bits in atomic variable
151 * @mask: Mask of the bits to be cleared
152 * @v: pointer of type atomic_t
154 * Atomically clears the bits set in @mask from @v
156 #ifndef atomic_clear_mask
157 static inline void atomic_clear_mask(unsigned long mask, atomic_t *v)
162 raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
164 raw_local_irq_restore(flags);
169 * atomic_set_mask - Atomically set bits in atomic variable
170 * @mask: Mask of the bits to be set
171 * @v: pointer of type atomic_t
173 * Atomically sets the bits set in @mask in @v
175 #ifndef atomic_set_mask
176 static inline void atomic_set_mask(unsigned int mask, atomic_t *v)
180 raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
182 raw_local_irq_restore(flags);
186 #endif /* __KERNEL__ */
187 #endif /* __ASM_GENERIC_ATOMIC_H */