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[PATCH] CPU hotplug compatible alloc_percpu()

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This patch splits alloc_percpu() up into two phases.  Likewise for
free_percpu().  This allows clients to limit initial allocations to online
cpu's, and to populate or depopulate per-cpu data at run time as needed:

  struct my_struct *obj;

  /* initial allocation for online cpu's */
  obj = percpu_alloc(sizeof(struct my_struct), GFP_KERNEL);

  ...

  /* populate per-cpu data for cpu coming online */
  ptr = percpu_populate(obj, sizeof(struct my_struct), GFP_KERNEL, cpu);

  ...

  /* access per-cpu object */
  ptr = percpu_ptr(obj, smp_processor_id());

  ...

  /* depopulate per-cpu data for cpu going offline */
  percpu_depopulate(obj, cpu);

  ...

  /* final removal */
  percpu_free(obj);

Signed-off-by: Martin Peschke <mp3@de.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Martin Peschke 2006-09-25 23:31:21 -07:00 • committed by Linus Torvalds
parent 8bc719d3ca
commit 7ff6f08295
2 changed files with 173 additions and 80 deletions
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79
include/linux/percpu.h
View file

@ -1,9 +1,12 @@
#ifndef __LINUX_PERCPU_H
#define __LINUX_PERCPU_H
#include <linux/spinlock.h> /* For preempt_disable() */
#include <linux/slab.h> /* For kmalloc() */
#include <linux/smp.h>
#include <linux/string.h> /* For memset() */
#include <linux/cpumask.h>
#include <asm/percpu.h>
/* Enough to cover all DEFINE_PER_CPUs in kernel, including modules. */
@ -27,39 +30,77 @@ struct percpu_data {
void *ptrs[NR_CPUS];
};
#define __percpu_disguise(pdata) (struct percpu_data *)~(unsigned long)(pdata)
/*
* Use this to get to a cpu's version of the per-cpu object allocated using
* alloc_percpu. Non-atomic access to the current CPU's version should
* Use this to get to a cpu's version of the per-cpu object dynamically
* allocated. Non-atomic access to the current CPU's version should
* probably be combined with get_cpu()/put_cpu().
*/
#define per_cpu_ptr(ptr, cpu) \
({ \
struct percpu_data *__p = (struct percpu_data *)~(unsigned long)(ptr); \
(__typeof__(ptr))__p->ptrs[(cpu)]; \
#define percpu_ptr(ptr, cpu) \
({ \
struct percpu_data *__p = __percpu_disguise(ptr); \
(__typeof__(ptr))__p->ptrs[(cpu)]; \
})
extern void *__alloc_percpu(size_t size);
extern void free_percpu(const void *);
extern void *percpu_populate(void *__pdata, size_t size, gfp_t gfp, int cpu);
extern void percpu_depopulate(void *__pdata, int cpu);
extern int __percpu_populate_mask(void *__pdata, size_t size, gfp_t gfp,
cpumask_t *mask);
extern void __percpu_depopulate_mask(void *__pdata, cpumask_t *mask);
extern void *__percpu_alloc_mask(size_t size, gfp_t gfp, cpumask_t *mask);
extern void percpu_free(void *__pdata);
#else /* CONFIG_SMP */
#define per_cpu_ptr(ptr, cpu) ({ (void)(cpu); (ptr); })
#define percpu_ptr(ptr, cpu) ({ (void)(cpu); (ptr); })
static inline void *__alloc_percpu(size_t size)
static inline void percpu_depopulate(void *__pdata, int cpu)
{
void *ret = kmalloc(size, GFP_KERNEL);
if (ret)
memset(ret, 0, size);
return ret;
}
static inline void free_percpu(const void *ptr)
{
kfree(ptr);
static inline void __percpu_depopulate_mask(void *__pdata, cpumask_t *mask)
{
}
static inline void *percpu_populate(void *__pdata, size_t size, gfp_t gfp,
int cpu)
{
return percpu_ptr(__pdata, cpu);
}
static inline int __percpu_populate_mask(void *__pdata, size_t size, gfp_t gfp,
cpumask_t *mask)
{
return 0;
}
static inline void *__percpu_alloc_mask(size_t size, gfp_t gfp, cpumask_t *mask)
{
return kzalloc(size, gfp);
}
static inline void percpu_free(void *__pdata)
{
kfree(__pdata);
}
#endif /* CONFIG_SMP */
/* Simple wrapper for the common case: zeros memory. */
#define alloc_percpu(type) ((type *)(__alloc_percpu(sizeof(type))))
#define percpu_populate_mask(__pdata, size, gfp, mask) \
__percpu_populate_mask((__pdata), (size), (gfp), &(mask))
#define percpu_depopulate_mask(__pdata, mask) \
__percpu_depopulate_mask((__pdata), &(mask))
#define percpu_alloc_mask(size, gfp, mask) \
__percpu_alloc_mask((size), (gfp), &(mask))
#define percpu_alloc(size, gfp) percpu_alloc_mask((size), (gfp), cpu_online_map)
/* (legacy) interface for use without CPU hotplug handling */
#define __alloc_percpu(size) percpu_alloc_mask((size), GFP_KERNEL, \
cpu_possible_map)
#define alloc_percpu(type) (type *)__alloc_percpu(sizeof(type))
#define free_percpu(ptr) percpu_free((ptr))
#define per_cpu_ptr(ptr, cpu) percpu_ptr((ptr), (cpu))
#endif /* __LINUX_PERCPU_H */