144 lines
5.0 KiB
C
144 lines
5.0 KiB
C
#ifndef _LINUX_PERCPU_DEFS_H
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#define _LINUX_PERCPU_DEFS_H
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/*
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* Determine the real variable name from the name visible in the
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* kernel sources.
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*/
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#define per_cpu_var(var) per_cpu__##var
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/*
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* Base implementations of per-CPU variable declarations and definitions, where
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* the section in which the variable is to be placed is provided by the
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* 'sec' argument. This may be used to affect the parameters governing the
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* variable's storage.
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*
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* NOTE! The sections for the DECLARE and for the DEFINE must match, lest
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* linkage errors occur due the compiler generating the wrong code to access
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* that section.
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*/
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#define __PCPU_ATTRS(sec) \
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__attribute__((section(PER_CPU_BASE_SECTION sec))) \
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PER_CPU_ATTRIBUTES
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#define __PCPU_DUMMY_ATTRS \
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__attribute__((section(".discard"), unused))
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/*
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* s390 and alpha modules require percpu variables to be defined as
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* weak to force the compiler to generate GOT based external
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* references for them. This is necessary because percpu sections
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* will be located outside of the usually addressable area.
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*
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* This definition puts the following two extra restrictions when
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* defining percpu variables.
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*
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* 1. The symbol must be globally unique, even the static ones.
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* 2. Static percpu variables cannot be defined inside a function.
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*
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* Archs which need weak percpu definitions should define
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* ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
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*
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* To ensure that the generic code observes the above two
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* restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
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* definition is used for all cases.
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*/
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#if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
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/*
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* __pcpu_scope_* dummy variable is used to enforce scope. It
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* receives the static modifier when it's used in front of
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* DEFINE_PER_CPU() and will trigger build failure if
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* DECLARE_PER_CPU() is used for the same variable.
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*
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* __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
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* such that hidden weak symbol collision, which will cause unrelated
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* variables to share the same address, can be detected during build.
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*/
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#define DECLARE_PER_CPU_SECTION(type, name, sec) \
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extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
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extern __PCPU_ATTRS(sec) __typeof__(type) per_cpu__##name
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#define DEFINE_PER_CPU_SECTION(type, name, sec) \
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__PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
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__PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
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__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \
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__typeof__(type) per_cpu__##name
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#else
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/*
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* Normal declaration and definition macros.
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*/
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#define DECLARE_PER_CPU_SECTION(type, name, sec) \
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extern __PCPU_ATTRS(sec) __typeof__(type) per_cpu__##name
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#define DEFINE_PER_CPU_SECTION(type, name, sec) \
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__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \
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__typeof__(type) per_cpu__##name
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#endif
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/*
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* Variant on the per-CPU variable declaration/definition theme used for
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* ordinary per-CPU variables.
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*/
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#define DECLARE_PER_CPU(type, name) \
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DECLARE_PER_CPU_SECTION(type, name, "")
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#define DEFINE_PER_CPU(type, name) \
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DEFINE_PER_CPU_SECTION(type, name, "")
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/*
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* Declaration/definition used for per-CPU variables that must come first in
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* the set of variables.
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*/
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#define DECLARE_PER_CPU_FIRST(type, name) \
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DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
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#define DEFINE_PER_CPU_FIRST(type, name) \
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DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
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/*
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* Declaration/definition used for per-CPU variables that must be cacheline
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* aligned under SMP conditions so that, whilst a particular instance of the
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* data corresponds to a particular CPU, inefficiencies due to direct access by
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* other CPUs are reduced by preventing the data from unnecessarily spanning
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* cachelines.
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*
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* An example of this would be statistical data, where each CPU's set of data
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* is updated by that CPU alone, but the data from across all CPUs is collated
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* by a CPU processing a read from a proc file.
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*/
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#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \
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DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
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____cacheline_aligned_in_smp
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#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
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DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
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____cacheline_aligned_in_smp
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#define DECLARE_PER_CPU_ALIGNED(type, name) \
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DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
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____cacheline_aligned
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#define DEFINE_PER_CPU_ALIGNED(type, name) \
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DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
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____cacheline_aligned
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/*
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* Declaration/definition used for per-CPU variables that must be page aligned.
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*/
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#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
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DECLARE_PER_CPU_SECTION(type, name, ".page_aligned") \
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__aligned(PAGE_SIZE)
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#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
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DEFINE_PER_CPU_SECTION(type, name, ".page_aligned") \
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__aligned(PAGE_SIZE)
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/*
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* Intermodule exports for per-CPU variables.
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*/
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#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
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#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
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#endif /* _LINUX_PERCPU_DEFS_H */
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