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Linux/include/asm-generic/atomic.h

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

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