Commit 5028eaa9 authored by David Howells's avatar David Howells Committed by Linus Torvalds
Browse files

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: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9b8de747

include/asm-generic/percpu.h

+2 −24
Original line number Diff line number Diff line 
#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_ */

include/linux/percpu-defs.h

0 → 100644
+84 −0
Original line number Diff line number Diff line 
#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 */

include/linux/percpu.h

+0 −20
Original line number Diff line number Diff line
@@ -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)

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