Linux kernel mirror (for testing)
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linux
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 <asm/cache.h>
7
8#ifndef L1_CACHE_ALIGN
9#define L1_CACHE_ALIGN(x) __ALIGN_KERNEL(x, L1_CACHE_BYTES)
10#endif
11
12#ifndef SMP_CACHE_BYTES
13#define SMP_CACHE_BYTES L1_CACHE_BYTES
14#endif
15
16/**
17 * SMP_CACHE_ALIGN - align a value to the L2 cacheline size
18 * @x: value to align
19 *
20 * On some architectures, L2 ("SMP") CL size is bigger than L1, and sometimes,
21 * this needs to be accounted.
22 *
23 * Return: aligned value.
24 */
25#ifndef SMP_CACHE_ALIGN
26#define SMP_CACHE_ALIGN(x) ALIGN(x, SMP_CACHE_BYTES)
27#endif
28
29/*
30 * ``__aligned_largest`` aligns a field to the value most optimal for the
31 * target architecture to perform memory operations. Get the actual value
32 * to be able to use it anywhere else.
33 */
34#ifndef __LARGEST_ALIGN
35#define __LARGEST_ALIGN sizeof(struct { long x; } __aligned_largest)
36#endif
37
38#ifndef LARGEST_ALIGN
39#define LARGEST_ALIGN(x) ALIGN(x, __LARGEST_ALIGN)
40#endif
41
42/*
43 * __read_mostly is used to keep rarely changing variables out of frequently
44 * updated cachelines. Its use should be reserved for data that is used
45 * frequently in hot paths. Performance traces can help decide when to use
46 * this. You want __read_mostly data to be tightly packed, so that in the
47 * best case multiple frequently read variables for a hot path will be next
48 * to each other in order to reduce the number of cachelines needed to
49 * execute a critical path. We should be mindful and selective of its use.
50 * ie: if you're going to use it please supply a *good* justification in your
51 * commit log
52 */
53#ifndef __read_mostly
54#define __read_mostly
55#endif
56
57/*
58 * __ro_after_init is used to mark things that are read-only after init (i.e.
59 * after mark_rodata_ro() has been called). These are effectively read-only,
60 * but may get written to during init, so can't live in .rodata (via "const").
61 */
62#ifndef __ro_after_init
63#define __ro_after_init __section(".data..ro_after_init")
64#endif
65
66#ifndef ____cacheline_aligned
67#define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES)))
68#endif
69
70#ifndef ____cacheline_aligned_in_smp
71#ifdef CONFIG_SMP
72#define ____cacheline_aligned_in_smp ____cacheline_aligned
73#else
74#define ____cacheline_aligned_in_smp
75#endif /* CONFIG_SMP */
76#endif
77
78#ifndef __cacheline_aligned
79#define __cacheline_aligned \
80 __attribute__((__aligned__(SMP_CACHE_BYTES), \
81 __section__(".data..cacheline_aligned")))
82#endif /* __cacheline_aligned */
83
84#ifndef __cacheline_aligned_in_smp
85#ifdef CONFIG_SMP
86#define __cacheline_aligned_in_smp __cacheline_aligned
87#else
88#define __cacheline_aligned_in_smp
89#endif /* CONFIG_SMP */
90#endif
91
92/*
93 * The maximum alignment needed for some critical structures
94 * These could be inter-node cacheline sizes/L3 cacheline
95 * size etc. Define this in asm/cache.h for your arch
96 */
97#ifndef INTERNODE_CACHE_SHIFT
98#define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT
99#endif
100
101#if !defined(____cacheline_internodealigned_in_smp)
102#if defined(CONFIG_SMP)
103#define ____cacheline_internodealigned_in_smp \
104 __attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT))))
105#else
106#define ____cacheline_internodealigned_in_smp
107#endif
108#endif
109
110#ifndef CONFIG_ARCH_HAS_CACHE_LINE_SIZE
111#define cache_line_size() L1_CACHE_BYTES
112#endif
113
114#ifndef __cacheline_group_begin
115#define __cacheline_group_begin(GROUP) \
116 __u8 __cacheline_group_begin__##GROUP[0]
117#endif
118
119#ifndef __cacheline_group_end
120#define __cacheline_group_end(GROUP) \
121 __u8 __cacheline_group_end__##GROUP[0]
122#endif
123
124/**
125 * __cacheline_group_begin_aligned - declare an aligned group start
126 * @GROUP: name of the group
127 * @...: optional group alignment
128 *
129 * The following block inside a struct:
130 *
131 * __cacheline_group_begin_aligned(grp);
132 * field a;
133 * field b;
134 * __cacheline_group_end_aligned(grp);
135 *
136 * will always be aligned to either the specified alignment or
137 * ``SMP_CACHE_BYTES``.
138 */
139#define __cacheline_group_begin_aligned(GROUP, ...) \
140 __cacheline_group_begin(GROUP) \
141 __aligned((__VA_ARGS__ + 0) ? : SMP_CACHE_BYTES)
142
143/**
144 * __cacheline_group_end_aligned - declare an aligned group end
145 * @GROUP: name of the group
146 * @...: optional alignment (same as was in __cacheline_group_begin_aligned())
147 *
148 * Note that the end marker is aligned to sizeof(long) to allow more precise
149 * size assertion. It also declares a padding at the end to avoid next field
150 * falling into this cacheline.
151 */
152#define __cacheline_group_end_aligned(GROUP, ...) \
153 __cacheline_group_end(GROUP) __aligned(sizeof(long)); \
154 struct { } __cacheline_group_pad__##GROUP \
155 __aligned((__VA_ARGS__ + 0) ? : SMP_CACHE_BYTES)
156
157#ifndef CACHELINE_ASSERT_GROUP_MEMBER
158#define CACHELINE_ASSERT_GROUP_MEMBER(TYPE, GROUP, MEMBER) \
159 BUILD_BUG_ON(!(offsetof(TYPE, MEMBER) >= \
160 offsetofend(TYPE, __cacheline_group_begin__##GROUP) && \
161 offsetofend(TYPE, MEMBER) <= \
162 offsetof(TYPE, __cacheline_group_end__##GROUP)))
163#endif
164
165#ifndef CACHELINE_ASSERT_GROUP_SIZE
166#define CACHELINE_ASSERT_GROUP_SIZE(TYPE, GROUP, SIZE) \
167 BUILD_BUG_ON(offsetof(TYPE, __cacheline_group_end__##GROUP) - \
168 offsetofend(TYPE, __cacheline_group_begin__##GROUP) > \
169 SIZE)
170#endif
171
172/*
173 * Helper to add padding within a struct to ensure data fall into separate
174 * cachelines.
175 */
176#if defined(CONFIG_SMP)
177struct cacheline_padding {
178 char x[0];
179} ____cacheline_internodealigned_in_smp;
180#define CACHELINE_PADDING(name) struct cacheline_padding name
181#else
182#define CACHELINE_PADDING(name)
183#endif
184
185#ifdef ARCH_DMA_MINALIGN
186#define ARCH_HAS_DMA_MINALIGN
187#else
188#define ARCH_DMA_MINALIGN __alignof__(unsigned long long)
189#endif
190
191#endif /* __LINUX_CACHE_H */