local.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _ASM_X86_LOCAL_H
  3#define _ASM_X86_LOCAL_H
  4
  5#include <linux/percpu.h>
  6
  7#include <linux/atomic.h>
  8#include <asm/asm.h>
  9
 10typedef struct {
 11	atomic_long_t a;
 12} local_t;
 13
 14#define LOCAL_INIT(i)	{ ATOMIC_LONG_INIT(i) }
 15
 16#define local_read(l)	atomic_long_read(&(l)->a)
 17#define local_set(l, i)	atomic_long_set(&(l)->a, (i))
 18
 19static inline void local_inc(local_t *l)
 20{
 21	asm volatile(_ASM_INC "%0"
 22		     : "+m" (l->a.counter));
 23}
 24
 25static inline void local_dec(local_t *l)
 26{
 27	asm volatile(_ASM_DEC "%0"
 28		     : "+m" (l->a.counter));
 29}
 30
 31static inline void local_add(long i, local_t *l)
 32{
 33	asm volatile(_ASM_ADD "%1,%0"
 34		     : "+m" (l->a.counter)
 35		     : "ir" (i));
 36}
 37
 38static inline void local_sub(long i, local_t *l)
 39{
 40	asm volatile(_ASM_SUB "%1,%0"
 41		     : "+m" (l->a.counter)
 42		     : "ir" (i));
 43}
 44
 45/**
 46 * local_sub_and_test - subtract value from variable and test result
 47 * @i: integer value to subtract
 48 * @l: pointer to type local_t
 49 *
 50 * Atomically subtracts @i from @l and returns
 51 * true if the result is zero, or false for all
 52 * other cases.
 53 */
 54static inline bool local_sub_and_test(long i, local_t *l)
 55{
 56	return GEN_BINARY_RMWcc(_ASM_SUB, l->a.counter, e, "er", i);
 57}
 58
 59/**
 60 * local_dec_and_test - decrement and test
 61 * @l: pointer to type local_t
 62 *
 63 * Atomically decrements @l by 1 and
 64 * returns true if the result is 0, or false for all other
 65 * cases.
 66 */
 67static inline bool local_dec_and_test(local_t *l)
 68{
 69	return GEN_UNARY_RMWcc(_ASM_DEC, l->a.counter, e);
 70}
 71
 72/**
 73 * local_inc_and_test - increment and test
 74 * @l: pointer to type local_t
 75 *
 76 * Atomically increments @l by 1
 77 * and returns true if the result is zero, or false for all
 78 * other cases.
 79 */
 80static inline bool local_inc_and_test(local_t *l)
 81{
 82	return GEN_UNARY_RMWcc(_ASM_INC, l->a.counter, e);
 83}
 84
 85/**
 86 * local_add_negative - add and test if negative
 87 * @i: integer value to add
 88 * @l: pointer to type local_t
 89 *
 90 * Atomically adds @i to @l and returns true
 91 * if the result is negative, or false when
 92 * result is greater than or equal to zero.
 93 */
 94static inline bool local_add_negative(long i, local_t *l)
 95{
 96	return GEN_BINARY_RMWcc(_ASM_ADD, l->a.counter, s, "er", i);
 97}
 98
 99/**
100 * local_add_return - add and return
101 * @i: integer value to add
102 * @l: pointer to type local_t
103 *
104 * Atomically adds @i to @l and returns @i + @l
105 */
106static inline long local_add_return(long i, local_t *l)
107{
108	long __i = i;
109	asm volatile(_ASM_XADD "%0, %1;"
110		     : "+r" (i), "+m" (l->a.counter)
111		     : : "memory");
112	return i + __i;
113}
114
115static inline long local_sub_return(long i, local_t *l)
116{
117	return local_add_return(-i, l);
118}
119
120#define local_inc_return(l)  (local_add_return(1, l))
121#define local_dec_return(l)  (local_sub_return(1, l))
122
123static inline long local_cmpxchg(local_t *l, long old, long new)
124{
125	return cmpxchg_local(&l->a.counter, old, new);
126}
127
128static inline bool local_try_cmpxchg(local_t *l, long *old, long new)
129{
130	return try_cmpxchg_local(&l->a.counter,
131				 (typeof(l->a.counter) *) old, new);
132}
133
134/*
135 * Implement local_xchg using CMPXCHG instruction without the LOCK prefix.
136 * XCHG is expensive due to the implied LOCK prefix.  The processor
137 * cannot prefetch cachelines if XCHG is used.
138 */
139static __always_inline long
140local_xchg(local_t *l, long n)
141{
142	long c = local_read(l);
143
144	do { } while (!local_try_cmpxchg(l, &c, n));
145
146	return c;
147}
148
149/**
150 * local_add_unless - add unless the number is already a given value
151 * @l: pointer of type local_t
152 * @a: the amount to add to l...
153 * @u: ...unless l is equal to u.
154 *
155 * Atomically adds @a to @l, if @v was not already @u.
156 * Returns true if the addition was done.
157 */
158static __always_inline bool
159local_add_unless(local_t *l, long a, long u)
160{
161	long c = local_read(l);
162
163	do {
164		if (unlikely(c == u))
165			return false;
166	} while (!local_try_cmpxchg(l, &c, c + a));
167
168	return true;
169}
170
171#define local_inc_not_zero(l) local_add_unless((l), 1, 0)
172
173/* On x86_32, these are no better than the atomic variants.
174 * On x86-64 these are better than the atomic variants on SMP kernels
175 * because they dont use a lock prefix.
176 */
177#define __local_inc(l)		local_inc(l)
178#define __local_dec(l)		local_dec(l)
179#define __local_add(i, l)	local_add((i), (l))
180#define __local_sub(i, l)	local_sub((i), (l))
181
182#endif /* _ASM_X86_LOCAL_H */