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#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 <asm/percpu.h>
/* Enough to cover all DEFINE_PER_CPUs in kernel, including modules. */
#ifndef PERCPU_ENOUGH_ROOM
#define PERCPU_ENOUGH_ROOM 32768
#endif
/* Must be an lvalue. */
#define get_cpu_var(var) (*({ preempt_disable(); &__get_cpu_var(var); }))
#define put_cpu_var(var) preempt_enable()
#ifdef CONFIG_SMP
struct percpu_data {
void *ptrs[NR_CPUS];
void *blkp;
};
/*
* Use this to get to a cpu's version of the per-cpu object allocated using
* alloc_percpu. If you want to get "this cpu's version", maybe you want
* to use get_cpu_ptr...
*/
#define per_cpu_ptr(ptr, cpu) \
({ \
struct percpu_data *__p = (struct percpu_data *)~(unsigned long)(ptr); \
(__typeof__(ptr))__p->ptrs[(cpu)]; \
})
extern void *__alloc_percpu(size_t size, size_t align);
extern void free_percpu(const void *);
extern void kmalloc_percpu_init(void);
#else /* CONFIG_SMP */
#define per_cpu_ptr(ptr, cpu) (ptr)
static inline void *__alloc_percpu(size_t size, size_t align)
{
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 kmalloc_percpu_init(void) { }
#endif /* CONFIG_SMP */
/* Simple wrapper for the common case: zeros memory. */
#define alloc_percpu(type) \
((type *)(__alloc_percpu(sizeof(type), __alignof__(type))))
/*
* Use these with alloc_percpu. If
* 1. You want to operate on memory allocated by alloc_percpu (dereference
* and read/modify/write) AND
* 2. You want "this cpu's version" of the object AND
* 3. You want to do this safely since:
* a. On multiprocessors, you don't want to switch between cpus after
* you've read the current processor id due to preemption -- this would
* take away the implicit advantage to not have any kind of traditional
* serialization for per-cpu data
* b. On uniprocessors, you don't want another kernel thread messing
* up with the same per-cpu data due to preemption
*
* So, Use get_cpu_ptr to disable preemption and get pointer to the
* local cpu version of the per-cpu object. Use put_cpu_ptr to enable
* preemption. Operations on per-cpu data between get_ and put_ is
* then considered to be safe. And ofcourse, "Thou shalt not sleep between
* get_cpu_ptr and put_cpu_ptr"
*/
#define get_cpu_ptr(ptr) per_cpu_ptr(ptr, get_cpu())
#define put_cpu_ptr(ptr) put_cpu()
#endif /* __LINUX_PERCPU_H */
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