root/include/linux/percpu_ida.h

INCLUDED FROM

DEFINITIONS

1. percpu_ida_init

#ifndef __PERCPU_IDA_H__
#define __PERCPU_IDA_H__

#include <linux/types.h>
#include <linux/bitops.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/spinlock_types.h>
#include <linux/wait.h>
#include <linux/cpumask.h>

struct percpu_ida_cpu;

struct percpu_ida {
        /*
         * number of tags available to be allocated, as passed to
         * percpu_ida_init()
         */
        unsigned                        nr_tags;
        unsigned                        percpu_max_size;
        unsigned                        percpu_batch_size;

        struct percpu_ida_cpu __percpu  *tag_cpu;

        /*
         * Bitmap of cpus that (may) have tags on their percpu freelists:
         * steal_tags() uses this to decide when to steal tags, and which cpus
         * to try stealing from.
         *
         * It's ok for a freelist to be empty when its bit is set - steal_tags()
         * will just keep looking - but the bitmap _must_ be set whenever a
         * percpu freelist does have tags.
         */
        cpumask_t                       cpus_have_tags;

        struct {
                spinlock_t              lock;
                /*
                 * When we go to steal tags from another cpu (see steal_tags()),
                 * we want to pick a cpu at random. Cycling through them every
                 * time we steal is a bit easier and more or less equivalent:
                 */
                unsigned                cpu_last_stolen;

                /* For sleeping on allocation failure */
                wait_queue_head_t       wait;

                /*
                 * Global freelist - it's a stack where nr_free points to the
                 * top
                 */
                unsigned                nr_free;
                unsigned                *freelist;
        } ____cacheline_aligned_in_smp;
};

/*
 * Number of tags we move between the percpu freelist and the global freelist at
 * a time
 */
#define IDA_DEFAULT_PCPU_BATCH_MOVE     32U
/* Max size of percpu freelist, */
#define IDA_DEFAULT_PCPU_SIZE   ((IDA_DEFAULT_PCPU_BATCH_MOVE * 3) / 2)

int percpu_ida_alloc(struct percpu_ida *pool, int state);
void percpu_ida_free(struct percpu_ida *pool, unsigned tag);

void percpu_ida_destroy(struct percpu_ida *pool);
int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
        unsigned long max_size, unsigned long batch_size);
static inline int percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags)
{
        return __percpu_ida_init(pool, nr_tags, IDA_DEFAULT_PCPU_SIZE,
                IDA_DEFAULT_PCPU_BATCH_MOVE);
}

typedef int (*percpu_ida_cb)(unsigned, void *);
int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
        void *data);

unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu);
#endif /* __PERCPU_IDA_H__ */