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PERCPU: Collect the DECLARE/DEFINE declarations together 

Collect the DECLARE/DEFINE declarations together in linux/percpu-defs.h so
that they're in one place, and give them descriptive comments, particularly
the SHARED_ALIGNED variant.

It would be nice to collect these in linux/percpu.h, but that's not possible
without sorting out the severe #include recursion between the x86 arch headers
and the general headers (and possibly other arches too).

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Howells 2009-04-21 23:00:29 +01:00 committed by Linus Torvalds
parent 9b8de7479d
commit 5028eaa97d
3 changed files with 86 additions and 44 deletions
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26
include/asm-generic/percpu.h
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@ -1,13 +1,9 @@
#ifndef _ASM_GENERIC_PERCPU_H_
#define _ASM_GENERIC_PERCPU_H_
#include <linux/compiler.h>
#include <linux/threads.h>
/*
* Determine the real variable name from the name visible in the
* kernel sources.
*/
#define per_cpu_var(var) per_cpu__##var
#include <linux/percpu-defs.h>
#ifdef CONFIG_SMP
@ -101,22 +97,4 @@ extern void setup_per_cpu_areas(void);
#define PER_CPU_ATTRIBUTES
#endif
#define DECLARE_PER_CPU_SECTION(type, name, section) \
extern \
__attribute__((__section__(PER_CPU_BASE_SECTION section))) \
PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name
#define DECLARE_PER_CPU(type, name) \
DECLARE_PER_CPU_SECTION(type, name, "")
#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
____cacheline_aligned_in_smp
#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, ".page_aligned")
#define DECLARE_PER_CPU_FIRST(type, name) \
DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
#endif /* _ASM_GENERIC_PERCPU_H_ */

84
include/linux/percpu-defs.h Normal file
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@ -0,0 +1,84 @@
#ifndef _LINUX_PERCPU_DEFS_H
#define _LINUX_PERCPU_DEFS_H
/*
* Determine the real variable name from the name visible in the
* kernel sources.
*/
#define per_cpu_var(var) per_cpu__##var
/*
* Base implementations of per-CPU variable declarations and definitions, where
* the section in which the variable is to be placed is provided by the
* 'section' argument. This may be used to affect the parameters governing the
* variable's storage.
*
* NOTE! The sections for the DECLARE and for the DEFINE must match, lest
* linkage errors occur due the compiler generating the wrong code to access
* that section.
*/
#define DECLARE_PER_CPU_SECTION(type, name, section) \
extern \
__attribute__((__section__(PER_CPU_BASE_SECTION section))) \
PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name
#define DEFINE_PER_CPU_SECTION(type, name, section) \
__attribute__((__section__(PER_CPU_BASE_SECTION section))) \
PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name
/*
* Variant on the per-CPU variable declaration/definition theme used for
* ordinary per-CPU variables.
*/
#define DECLARE_PER_CPU(type, name) \
DECLARE_PER_CPU_SECTION(type, name, "")
#define DEFINE_PER_CPU(type, name) \
DEFINE_PER_CPU_SECTION(type, name, "")
/*
* Declaration/definition used for per-CPU variables that must come first in
* the set of variables.
*/
#define DECLARE_PER_CPU_FIRST(type, name) \
DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
#define DEFINE_PER_CPU_FIRST(type, name) \
DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
/*
* Declaration/definition used for per-CPU variables that must be cacheline
* aligned under SMP conditions so that, whilst a particular instance of the
* data corresponds to a particular CPU, inefficiencies due to direct access by
* other CPUs are reduced by preventing the data from unnecessarily spanning
* cachelines.
*
* An example of this would be statistical data, where each CPU's set of data
* is updated by that CPU alone, but the data from across all CPUs is collated
* by a CPU processing a read from a proc file.
*/
#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
____cacheline_aligned_in_smp
#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
____cacheline_aligned_in_smp
/*
* Declaration/definition used for per-CPU variables that must be page aligned.
*/
#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, ".page_aligned")
#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, ".page_aligned")
/*
* Intermodule exports for per-CPU variables.
*/
#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
#endif /* _LINUX_PERCPU_DEFS_H */

20
include/linux/percpu.h
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@ -9,26 +9,6 @@
#include <asm/percpu.h>
#define DEFINE_PER_CPU_SECTION(type, name, section) \
__attribute__((__section__(PER_CPU_BASE_SECTION section))) \
PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name
#define DEFINE_PER_CPU(type, name) \
DEFINE_PER_CPU_SECTION(type, name, "")
#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
____cacheline_aligned_in_smp
#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, ".page_aligned")
#define DEFINE_PER_CPU_FIRST(type, name) \
DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
/* enough to cover all DEFINE_PER_CPUs in modules */
#ifdef CONFIG_MODULES
#define PERCPU_MODULE_RESERVE (8 << 10)