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Commit c50cbb05 authored by Ben Hutchings's avatar Ben Hutchings Committed by Ingo Molnar
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cpu topology: always define CPU topology information 

This can result in an empty topology directory in sysfs, and requires
in-kernel users to protect all uses with #ifdef - see
<http://marc.info/?l=linux-netdev&m=120639033904472&w=2

>.

The documentation of CPU topology specifies what the defaults should be if
only partial information is available from the hardware.  So we can
provide these defaults as a fallback.

This patch:

- Adds default definitions of the 4 topology macros to <linux/topology.h>
- Changes drivers/base/topology.c to use the topology macros unconditionally
  and to cope with definitions that aren't lvalues
- Updates documentation accordingly

[ From: Andrew Morton <akpm@linux-foundation.org>
  - fold now-duplicated code
  - fix layout
]

Signed-off-by: default avatarBen Hutchings <bhutchings@solarflare.com>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Chandra Seetharaman <sekharan@us.ibm.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Mike Travis <travis@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: John Hawkes <hawkes@sgi.com>
Cc: Zhang, Yanmin <yanmin.zhang@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent aab2545f

Documentation/cputopology.txt

+9 −17
Original line number Diff line number Diff line
@@ -14,9 +14,8 @@ represent the thread siblings to cpu X in the same physical package; 
To implement it in an architecture-neutral way, a new source file,

drivers/base/topology.c, is to export the 4 attributes.



If one architecture wants to support this feature, it just needs to

implement 4 defines, typically in file include/asm-XXX/topology.h.

The 4 defines are:

For an architecture to support this feature, it must define some of

these macros in include/asm-XXX/topology.h:

#define topology_physical_package_id(cpu)

#define topology_core_id(cpu)

#define topology_thread_siblings(cpu)
@@ -25,17 +24,10 @@ The 4 defines are: 
The type of **_id is int.

The type of siblings is cpumask_t.



To be consistent on all architectures, the 4 attributes should have

default values if their values are unavailable. Below is the rule.

1) physical_package_id: If cpu has no physical package id, -1 is the

default value.

2) core_id: If cpu doesn't support multi-core, its core id is 0.

3) thread_siblings: Just include itself, if the cpu doesn't support

HT/multi-thread.

4) core_siblings: Just include itself, if the cpu doesn't support

multi-core and HT/Multi-thread.



So be careful when declaring the 4 defines in include/asm-XXX/topology.h.



If an attribute isn't defined on an architecture, it won't be exported.

To be consistent on all architectures, include/linux/topology.h

provides default definitions for any of the above macros that are

not defined by include/asm-XXX/topology.h:

1) physical_package_id: -1

2) core_id: 0

3) thread_siblings: just the given CPU

4) core_siblings: just the given CPU

drivers/base/topology.c

+10 −28
Original line number Diff line number Diff line
@@ -59,60 +59,42 @@ static ssize_t show_cpumap(int type, cpumask_t *mask, char *buf) 
static inline ssize_t show_##name(struct sys_device *dev, char *buf)	\

{									\

	unsigned int cpu = dev->id;					\

	return show_cpumap(0, &(topology_##name(cpu)), buf);		\

	cpumask_t siblings = topology_##name(cpu);			\

	return show_cpumap(0, &siblings, buf);				\

}



#define define_siblings_show_list(name)					\

static inline ssize_t show_##name##_list(struct sys_device *dev, char *buf) \

{									\

	unsigned int cpu = dev->id;					\

	return show_cpumap(1, &(topology_##name(cpu)), buf);		\

	cpumask_t siblings = topology_##name(cpu);			\

	return show_cpumap(1, &siblings, buf);				\

}



#define define_siblings_show_func(name)		\

	define_siblings_show_map(name); define_siblings_show_list(name)



#ifdef	topology_physical_package_id

define_id_show_func(physical_package_id);

define_one_ro(physical_package_id);

#define ref_physical_package_id_attr	&attr_physical_package_id.attr,

#else

#define ref_physical_package_id_attr

#endif



#ifdef topology_core_id

define_id_show_func(core_id);

define_one_ro(core_id);

#define ref_core_id_attr		&attr_core_id.attr,

#else

#define ref_core_id_attr

#endif



#ifdef topology_thread_siblings

define_siblings_show_func(thread_siblings);

define_one_ro(thread_siblings);

define_one_ro(thread_siblings_list);

#define ref_thread_siblings_attr	\

		&attr_thread_siblings.attr, &attr_thread_siblings_list.attr,

#else

#define ref_thread_siblings_attr

#endif



#ifdef topology_core_siblings

define_siblings_show_func(core_siblings);

define_one_ro(core_siblings);

define_one_ro(core_siblings_list);

#define ref_core_siblings_attr		\

		&attr_core_siblings.attr, &attr_core_siblings_list.attr,

#else

#define ref_core_siblings_attr

#endif



static struct attribute *default_attrs[] = {

	ref_physical_package_id_attr

	ref_core_id_attr

	ref_thread_siblings_attr

	ref_core_siblings_attr

	&attr_physical_package_id.attr,

	&attr_core_id.attr,

	&attr_thread_siblings.attr,

	&attr_thread_siblings_list.attr,

	&attr_core_siblings.attr,

	&attr_core_siblings_list.attr,

	NULL

};

include/linux/topology.h

+13 −0
Original line number Diff line number Diff line
@@ -179,4 +179,17 @@ void arch_update_cpu_topology(void); 
#endif

#endif /* CONFIG_NUMA */



#ifndef topology_physical_package_id

#define topology_physical_package_id(cpu)	((void)(cpu), -1)

#endif

#ifndef topology_core_id

#define topology_core_id(cpu)			((void)(cpu), 0)

#endif

#ifndef topology_thread_siblings

#define topology_thread_siblings(cpu)		cpumask_of_cpu(cpu)

#endif

#ifndef topology_core_siblings

#define topology_core_siblings(cpu)		cpumask_of_cpu(cpu)

#endif



#endif /* _LINUX_TOPOLOGY_H */