/* * kref.c - library routines for handling generic reference counted objects * * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com> * Copyright (C) 2004 IBM Corp. * * based on lib/kobject.c which was: * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org> * * This file is released under the GPLv2. * */ #include <linux/kref.h> #include <linux/module.h> #include <linux/slab.h> /** * kref_set - initialize object and set refcount to requested number. * @kref: object in question. * @num: initial reference counter */ void kref_set(struct kref *kref, int num) { atomic_set(&kref->refcount, num); smp_mb(); } /** * kref_init - initialize object. * @kref: object in question. */ void kref_init(struct kref *kref) { kref_set(kref, 1); } /** * kref_get - increment refcount for object. * @kref: object. */ void kref_get(struct kref *kref) { WARN_ON(!atomic_read(&kref->refcount)); atomic_inc(&kref->refcount); smp_mb__after_atomic_inc(); } /** * kref_put - decrement refcount for object. * @kref: object. * @release: pointer to the function that will clean up the object when the * last reference to the object is released. * This pointer is required, and it is not acceptable to pass kfree * in as this function. * * Decrement the refcount, and if 0, call release(). * Return 1 if the object was removed, otherwise return 0. Beware, if this * function returns 0, you still can not count on the kref from remaining in * memory. Only use the return value if you want to see if the kref is now * gone, not present. */ int kref_put(struct kref *kref, void (*release)(struct kref *kref)) { WARN_ON(release == NULL); WARN_ON(release == (void (*)(struct kref *))kfree); if (atomic_dec_and_test(&kref->refcount)) { release(kref); return 1; } return 0; } EXPORT_SYMBOL(kref_set); EXPORT_SYMBOL(kref_init); EXPORT_SYMBOL(kref_get); EXPORT_SYMBOL(kref_put);