1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_CACHE_H
3#define __LINUX_CACHE_H
4
5#include <uapi/linux/kernel.h>
6#include <vdso/cache.h>
7#include <asm/cache.h>
8
9#ifndef L1_CACHE_ALIGN
10#define L1_CACHE_ALIGN(x) __ALIGN_KERNEL(x, L1_CACHE_BYTES)
11#endif
12
13/**
14 * SMP_CACHE_ALIGN - align a value to the L2 cacheline size
15 * @x: value to align
16 *
17 * On some architectures, L2 ("SMP") CL size is bigger than L1, and sometimes,
18 * this needs to be accounted.
19 *
20 * Return: aligned value.
21 */
22#ifndef SMP_CACHE_ALIGN
23#define SMP_CACHE_ALIGN(x) ALIGN(x, SMP_CACHE_BYTES)
24#endif
25
26/*
27 * ``__aligned_largest`` aligns a field to the value most optimal for the
28 * target architecture to perform memory operations. Get the actual value
29 * to be able to use it anywhere else.
30 */
31#ifndef __LARGEST_ALIGN
32#define __LARGEST_ALIGN sizeof(struct { long x; } __aligned_largest)
33#endif
34
35#ifndef LARGEST_ALIGN
36#define LARGEST_ALIGN(x) ALIGN(x, __LARGEST_ALIGN)
37#endif
38
39/*
40 * __read_mostly is used to keep rarely changing variables out of frequently
41 * updated cachelines. Its use should be reserved for data that is used
42 * frequently in hot paths. Performance traces can help decide when to use
43 * this. You want __read_mostly data to be tightly packed, so that in the
44 * best case multiple frequently read variables for a hot path will be next
45 * to each other in order to reduce the number of cachelines needed to
46 * execute a critical path. We should be mindful and selective of its use.
47 * ie: if you're going to use it please supply a *good* justification in your
48 * commit log
49 */
50#ifndef __read_mostly
51#define __read_mostly
52#endif
53
54/*
55 * __ro_after_init is used to mark things that are read-only after init (i.e.
56 * after mark_rodata_ro() has been called). These are effectively read-only,
57 * but may get written to during init, so can't live in .rodata (via "const").
58 */
59#ifndef __ro_after_init
60#define __ro_after_init __section(".data..ro_after_init")
61#endif
62
63#ifndef ____cacheline_aligned_in_smp
64#ifdef CONFIG_SMP
65#define ____cacheline_aligned_in_smp ____cacheline_aligned
66#else
67#define ____cacheline_aligned_in_smp
68#endif /* CONFIG_SMP */
69#endif
70
71#ifndef __cacheline_aligned
72#define __cacheline_aligned \
73 __attribute__((__aligned__(SMP_CACHE_BYTES), \
74 __section__(".data..cacheline_aligned")))
75#endif /* __cacheline_aligned */
76
77#ifndef __cacheline_aligned_in_smp
78#ifdef CONFIG_SMP
79#define __cacheline_aligned_in_smp __cacheline_aligned
80#else
81#define __cacheline_aligned_in_smp
82#endif /* CONFIG_SMP */
83#endif
84
85/*
86 * The maximum alignment needed for some critical structures
87 * These could be inter-node cacheline sizes/L3 cacheline
88 * size etc. Define this in asm/cache.h for your arch
89 */
90#ifndef INTERNODE_CACHE_SHIFT
91#define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT
92#endif
93
94#if !defined(____cacheline_internodealigned_in_smp)
95#if defined(CONFIG_SMP)
96#define ____cacheline_internodealigned_in_smp \
97 __attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT))))
98#else
99#define ____cacheline_internodealigned_in_smp
100#endif
101#endif
102
103#ifndef CONFIG_ARCH_HAS_CACHE_LINE_SIZE
104#define cache_line_size() L1_CACHE_BYTES
105#endif
106
107#ifndef __cacheline_group_begin
108#define __cacheline_group_begin(GROUP) \
109 __u8 __cacheline_group_begin__##GROUP[0]
110#endif
111
112#ifndef __cacheline_group_end
113#define __cacheline_group_end(GROUP) \
114 __u8 __cacheline_group_end__##GROUP[0]
115#endif
116
117/**
118 * __cacheline_group_begin_aligned - declare an aligned group start
119 * @GROUP: name of the group
120 * @...: optional group alignment
121 *
122 * The following block inside a struct:
123 *
124 * __cacheline_group_begin_aligned(grp);
125 * field a;
126 * field b;
127 * __cacheline_group_end_aligned(grp);
128 *
129 * will always be aligned to either the specified alignment or
130 * ``SMP_CACHE_BYTES``.
131 */
132#define __cacheline_group_begin_aligned(GROUP, ...) \
133 __cacheline_group_begin(GROUP) \
134 __aligned((__VA_ARGS__ + 0) ? : SMP_CACHE_BYTES)
135
136/**
137 * __cacheline_group_end_aligned - declare an aligned group end
138 * @GROUP: name of the group
139 * @...: optional alignment (same as was in __cacheline_group_begin_aligned())
140 *
141 * Note that the end marker is aligned to sizeof(long) to allow more precise
142 * size assertion. It also declares a padding at the end to avoid next field
143 * falling into this cacheline.
144 */
145#define __cacheline_group_end_aligned(GROUP, ...) \
146 __cacheline_group_end(GROUP) __aligned(sizeof(long)); \
147 struct { } __cacheline_group_pad__##GROUP \
148 __aligned((__VA_ARGS__ + 0) ? : SMP_CACHE_BYTES)
149
150#ifndef CACHELINE_ASSERT_GROUP_MEMBER
151#define CACHELINE_ASSERT_GROUP_MEMBER(TYPE, GROUP, MEMBER) \
152 BUILD_BUG_ON(!(offsetof(TYPE, MEMBER) >= \
153 offsetofend(TYPE, __cacheline_group_begin__##GROUP) && \
154 offsetofend(TYPE, MEMBER) <= \
155 offsetof(TYPE, __cacheline_group_end__##GROUP)))
156#endif
157
158#ifndef CACHELINE_ASSERT_GROUP_SIZE
159#define CACHELINE_ASSERT_GROUP_SIZE(TYPE, GROUP, SIZE) \
160 BUILD_BUG_ON(offsetof(TYPE, __cacheline_group_end__##GROUP) - \
161 offsetofend(TYPE, __cacheline_group_begin__##GROUP) > \
162 SIZE)
163#endif
164
165/*
166 * Helper to add padding within a struct to ensure data fall into separate
167 * cachelines.
168 */
169#if defined(CONFIG_SMP)
170struct cacheline_padding {
171 char x[0];
172} ____cacheline_internodealigned_in_smp;
173#define CACHELINE_PADDING(name) struct cacheline_padding name
174#else
175#define CACHELINE_PADDING(name)
176#endif
177
178#ifdef ARCH_DMA_MINALIGN
179#define ARCH_HAS_DMA_MINALIGN
180#else
181#define ARCH_DMA_MINALIGN __alignof__(unsigned long long)
182#endif
183
184#endif /* __LINUX_CACHE_H */
185

source code of linux/include/linux/cache.h

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