1/* 2 * kref.c - library routines for handling generic reference counted objects 3 * 4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com> 5 * Copyright (C) 2004 IBM Corp. 6 * 7 * based on lib/kobject.c which was: 8 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org> 9 * 10 * This file is released under the GPLv2. 11 * 12 */ 13 14#include <linux/kref.h> 15#include <linux/module.h> 16 17/** 18 * kref_init - initialize object. 19 * @kref: object in question. 20 */ 21void kref_init(struct kref *kref) 22{ 23 atomic_set(&kref->refcount,1); 24 smp_mb(); 25} 26 27/** 28 * kref_get - increment refcount for object. 29 * @kref: object. 30 */ 31void kref_get(struct kref *kref) 32{ 33 WARN_ON(!atomic_read(&kref->refcount)); 34 atomic_inc(&kref->refcount); 35 smp_mb__after_atomic_inc(); 36} 37 38/** 39 * kref_put - decrement refcount for object. 40 * @kref: object. 41 * @release: pointer to the function that will clean up the object when the 42 * last reference to the object is released. 43 * This pointer is required, and it is not acceptable to pass kfree 44 * in as this function. 45 * 46 * Decrement the refcount, and if 0, call release(). 47 * Return 1 if the object was removed, otherwise return 0. Beware, if this 48 * function returns 0, you still can not count on the kref from remaining in 49 * memory. Only use the return value if you want to see if the kref is now 50 * gone, not present. 51 */ 52int kref_put(struct kref *kref, void (*release)(struct kref *kref)) 53{ 54 WARN_ON(release == NULL); 55 WARN_ON(release == (void (*)(struct kref *))kfree); 56 57 if (atomic_dec_and_test(&kref->refcount)) { 58 release(kref); 59 return 1; 60 } 61 return 0; 62} 63 64EXPORT_SYMBOL(kref_init); 65EXPORT_SYMBOL(kref_get); 66EXPORT_SYMBOL(kref_put); 67