kref.h

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/*
 * kref.h - library routines for handling generic reference counted objects
 *
 * Copyright (C) 2004 Greg Kroah-Hartman <[email protected]>
 * Copyright (C) 2004 IBM Corp.
 *
 * based on kobject.h which was:
 * Copyright (C) 2002-2003 Patrick Mochel <[email protected]>
 * Copyright (C) 2002-2003 Open Source Development Labs
 *
 * This file is released under the GPLv2.
 *
 */

#ifndef _KREF_H_
#define _KREF_H_

#include <linux/bug.h>
#include <linux/atomic.h>
#include <linux/kernel.h>
#include <linux/mutex.h>

struct kref {
    atomic_t refcount;
};

static inline void kref_init(struct kref *kref)
{
    atomic_set(&kref->refcount, 1);
}

static inline void kref_get(struct kref *kref)
{
    WARN_ON(!atomic_read(&kref->refcount));
    atomic_inc(&kref->refcount);
}

static inline int kref_sub(struct kref *kref, unsigned int count,
         void (*release)(struct kref *kref))
{
    WARN_ON(release == NULL);

    if (atomic_sub_and_test((int) count, &kref->refcount)) {
        release(kref);
        return 1;
    }
    return 0;
}

static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref))
{
    return kref_sub(kref, 1, release);
}

static inline int kref_put_mutex(struct kref *kref,
                 void (*release)(struct kref *kref),
                 struct mutex *lock)
{
    WARN_ON(release == NULL);
        if (unlikely(!atomic_add_unless(&kref->refcount, -1, 1))) {
        mutex_lock(lock);
        if (unlikely(!atomic_dec_and_test(&kref->refcount))) {
            mutex_unlock(lock);
            return 0;
        }
        release(kref);
        return 1;
    }
    return 0;
}
#endif /* _KREF_H_ */