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 #include <asm/barrier.h> 20 21 /* 22 * atomic_$op() - $op integer to atomic variable 23 * @i: integer value to $op 24 * @v: pointer to the atomic variable 25 * 26 * Atomically $ops @i to @v. Does not strictly guarantee a memory-barrier, use 27 * smp_mb__{before,after}_atomic(). 28 */ 29 30 /* 31 * atomic_$op_return() - $op interer to atomic variable and returns the result 32 * @i: integer value to $op 33 * @v: pointer to the atomic variable 34 * 35 * Atomically $ops @i to @v. Does imply a full memory barrier. 36 */ 37 38 #ifdef CONFIG_SMP 39 40 /* we can build all atomic primitives from cmpxchg */ 41 42 #define ATOMIC_OP(op, c_op) \ 43 static inline void atomic_##op(int i, atomic_t *v) \ 44 { \ 45 int c, old; \ 46 \ 47 c = v->counter; \ 48 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \ 49 c = old; \ 50 } 51 52 #define ATOMIC_OP_RETURN(op, c_op) \ 53 static inline int atomic_##op##_return(int i, atomic_t *v) \ 54 { \ 55 int c, old; \ 56 \ 57 c = v->counter; \ 58 while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \ 59 c = old; \ 60 \ 61 return c c_op i; \ 62 } 63 64 #else 65 66 #include <linux/irqflags.h> 67 68 #define ATOMIC_OP(op, c_op) \ 69 static inline void atomic_##op(int i, atomic_t *v) \ 70 { \ 71 unsigned long flags; \ 72 \ 73 raw_local_irq_save(flags); \ 74 v->counter = v->counter c_op i; \ 75 raw_local_irq_restore(flags); \ 76 } 77 78 #define ATOMIC_OP_RETURN(op, c_op) \ 79 static inline int atomic_##op##_return(int i, atomic_t *v) \ 80 { \ 81 unsigned long flags; \ 82 int ret; \ 83 \ 84 raw_local_irq_save(flags); \ 85 ret = (v->counter = v->counter c_op i); \ 86 raw_local_irq_restore(flags); \ 87 \ 88 return ret; \ 89 } 90 91 #endif /* CONFIG_SMP */ 92 93 #ifndef atomic_add_return 94 ATOMIC_OP_RETURN(add, +) 95 #endif 96 97 #ifndef atomic_sub_return 98 ATOMIC_OP_RETURN(sub, -) 99 #endif 100 101 #ifndef atomic_clear_mask 102 ATOMIC_OP(and, &) 103 #define atomic_clear_mask(i, v) atomic_and(~(i), (v)) 104 #endif 105 106 #ifndef atomic_set_mask 107 #define CONFIG_ARCH_HAS_ATOMIC_OR 108 ATOMIC_OP(or, |) 109 #define atomic_set_mask(i, v) atomic_or((i), (v)) 110 #endif 111 112 #undef ATOMIC_OP_RETURN 113 #undef ATOMIC_OP 114 115 /* 116 * Atomic operations that C can't guarantee us. Useful for 117 * resource counting etc.. 118 */ 119 120 #define ATOMIC_INIT(i) { (i) } 121 122 /** 123 * atomic_read - read atomic variable 124 * @v: pointer of type atomic_t 125 * 126 * Atomically reads the value of @v. 127 */ 128 #ifndef atomic_read 129 #define atomic_read(v) ACCESS_ONCE((v)->counter) 130 #endif 131 132 /** 133 * atomic_set - set atomic variable 134 * @v: pointer of type atomic_t 135 * @i: required value 136 * 137 * Atomically sets the value of @v to @i. 138 */ 139 #define atomic_set(v, i) (((v)->counter) = (i)) 140 141 #include <linux/irqflags.h> 142 143 static inline int atomic_add_negative(int i, atomic_t *v) 144 { 145 return atomic_add_return(i, v) < 0; 146 } 147 148 static inline void atomic_add(int i, atomic_t *v) 149 { 150 atomic_add_return(i, v); 151 } 152 153 static inline void atomic_sub(int i, atomic_t *v) 154 { 155 atomic_sub_return(i, v); 156 } 157 158 static inline void atomic_inc(atomic_t *v) 159 { 160 atomic_add_return(1, v); 161 } 162 163 static inline void atomic_dec(atomic_t *v) 164 { 165 atomic_sub_return(1, v); 166 } 167 168 #define atomic_dec_return(v) atomic_sub_return(1, (v)) 169 #define atomic_inc_return(v) atomic_add_return(1, (v)) 170 171 #define atomic_sub_and_test(i, v) (atomic_sub_return((i), (v)) == 0) 172 #define atomic_dec_and_test(v) (atomic_dec_return(v) == 0) 173 #define atomic_inc_and_test(v) (atomic_inc_return(v) == 0) 174 175 #define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v))) 176 #define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new))) 177 178 static inline int __atomic_add_unless(atomic_t *v, int a, int u) 179 { 180 int c, old; 181 c = atomic_read(v); 182 while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c) 183 c = old; 184 return c; 185 } 186 187 #endif /* __ASM_GENERIC_ATOMIC_H */ 188