diff options
Diffstat (limited to 'lib/kref.c')
-rw-r--r-- | lib/kref.c | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/lib/kref.c b/lib/kref.c new file mode 100644 index 00000000..3efb882b --- /dev/null +++ b/lib/kref.c @@ -0,0 +1,97 @@ +/* + * 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_init - initialize object. + * @kref: object in question. + */ +void kref_init(struct kref *kref) +{ + atomic_set(&kref->refcount, 1); + smp_mb(); +} + +/** + * 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; +} + + +/** + * kref_sub - subtract a number of refcounts for object. + * @kref: object. + * @count: Number of recounts to subtract. + * @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. + * + * Subtract @count from 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_sub(struct kref *kref, unsigned int count, + void (*release)(struct kref *kref)) +{ + WARN_ON(release == NULL); + WARN_ON(release == (void (*)(struct kref *))kfree); + + if (atomic_sub_and_test((int) count, &kref->refcount)) { + release(kref); + return 1; + } + return 0; +} + +EXPORT_SYMBOL(kref_init); +EXPORT_SYMBOL(kref_get); +EXPORT_SYMBOL(kref_put); +EXPORT_SYMBOL(kref_sub); |