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- /* SPDX-License-Identifier: GPL-2.0 */
- #ifndef __LINUX_CACHE_H
- #define __LINUX_CACHE_H
- #include <uapi/linux/kernel.h>
- #include <asm/cache.h>
- #ifndef L1_CACHE_ALIGN
- #define L1_CACHE_ALIGN(x) __ALIGN_KERNEL(x, L1_CACHE_BYTES)
- #endif
- #ifndef SMP_CACHE_BYTES
- #define SMP_CACHE_BYTES L1_CACHE_BYTES
- #endif
- /*
- * __read_mostly is used to keep rarely changing variables out of frequently
- * updated cachelines. Its use should be reserved for data that is used
- * frequently in hot paths. Performance traces can help decide when to use
- * this. You want __read_mostly data to be tightly packed, so that in the
- * best case multiple frequently read variables for a hot path will be next
- * to each other in order to reduce the number of cachelines needed to
- * execute a critical path. We should be mindful and selective of its use.
- * ie: if you're going to use it please supply a *good* justification in your
- * commit log
- */
- #ifndef __read_mostly
- #define __read_mostly
- #endif
- /*
- * __ro_after_init is used to mark things that are read-only after init (i.e.
- * after mark_rodata_ro() has been called). These are effectively read-only,
- * but may get written to during init, so can't live in .rodata (via "const").
- */
- #ifndef __ro_after_init
- #define __ro_after_init __section(".data..ro_after_init")
- #endif
- #ifndef ____cacheline_aligned
- #define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES)))
- #endif
- #ifndef ____cacheline_aligned_in_smp
- #ifdef CONFIG_SMP
- #define ____cacheline_aligned_in_smp ____cacheline_aligned
- #else
- #define ____cacheline_aligned_in_smp
- #endif /* CONFIG_SMP */
- #endif
- #ifndef __cacheline_aligned
- #define __cacheline_aligned \
- __attribute__((__aligned__(SMP_CACHE_BYTES), \
- __section__(".data..cacheline_aligned")))
- #endif /* __cacheline_aligned */
- #ifndef __cacheline_aligned_in_smp
- #ifdef CONFIG_SMP
- #define __cacheline_aligned_in_smp __cacheline_aligned
- #else
- #define __cacheline_aligned_in_smp
- #endif /* CONFIG_SMP */
- #endif
- /*
- * The maximum alignment needed for some critical structures
- * These could be inter-node cacheline sizes/L3 cacheline
- * size etc. Define this in asm/cache.h for your arch
- */
- #ifndef INTERNODE_CACHE_SHIFT
- #define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT
- #endif
- #if !defined(____cacheline_internodealigned_in_smp)
- #if defined(CONFIG_SMP)
- #define ____cacheline_internodealigned_in_smp \
- __attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT))))
- #else
- #define ____cacheline_internodealigned_in_smp
- #endif
- #endif
- #ifndef CONFIG_ARCH_HAS_CACHE_LINE_SIZE
- #define cache_line_size() L1_CACHE_BYTES
- #endif
- /*
- * Helper to add padding within a struct to ensure data fall into separate
- * cachelines.
- */
- #if defined(CONFIG_SMP)
- struct cacheline_padding {
- char x[0];
- } ____cacheline_internodealigned_in_smp;
- #define CACHELINE_PADDING(name) struct cacheline_padding name
- #else
- #define CACHELINE_PADDING(name)
- #endif
- #endif /* __LINUX_CACHE_H */
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