projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 1da177e4 | 1 | /* |
| 932fb06b | 2 | * kref.h - library routines for handling generic reference counted objects |
| 1da177e4 LT |
3 | * |
| 4 | * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com> | |
| 5 | * Copyright (C) 2004 IBM Corp. | |
| 6 | * | |
| 7 | * based on kobject.h which was: | |
| 8 | * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org> | |
| 9 | * Copyright (C) 2002-2003 Open Source Development Labs | |
| 10 | * | |
| 11 | * This file is released under the GPLv2. | |
| 12 | * | |
| 13 | */ | |
| 14 | ||
| 15 | #ifndef _KREF_H_ | |
| 16 | #define _KREF_H_ | |
| 17 | ||
| 1da177e4 | 18 | #include <linux/types.h> |
| 4af679cd | 19 | #include <linux/slab.h> |
| 1da177e4 LT |
20 | |
| 21 | struct kref { | |
| 22 | atomic_t refcount; | |
| 23 | }; | |
| 24 | ||
| 4af679cd PZ |
25 | /** |
| 26 | * kref_init - initialize object. | |
| 27 | * @kref: object in question. | |
| 28 | */ | |
| 29 | static inline void kref_init(struct kref *kref) | |
| 30 | { | |
| 31 | atomic_set(&kref->refcount, 1); | |
| 32 | smp_mb(); | |
| 33 | } | |
| 34 | ||
| 35 | /** | |
| 36 | * kref_get - increment refcount for object. | |
| 37 | * @kref: object. | |
| 38 | */ | |
| 39 | static inline void kref_get(struct kref *kref) | |
| 40 | { | |
| 41 | WARN_ON(!atomic_read(&kref->refcount)); | |
| 42 | atomic_inc(&kref->refcount); | |
| 43 | smp_mb__after_atomic_inc(); | |
| 44 | } | |
| 45 | ||
| 46 | /** | |
| 47 | * kref_put - decrement refcount for object. | |
| 48 | * @kref: object. | |
| 49 | * @release: pointer to the function that will clean up the object when the | |
| 50 | * last reference to the object is released. | |
| 51 | * This pointer is required, and it is not acceptable to pass kfree | |
| 52 | * in as this function. | |
| 53 | * | |
| 54 | * Decrement the refcount, and if 0, call release(). | |
| 55 | * Return 1 if the object was removed, otherwise return 0. Beware, if this | |
| 56 | * function returns 0, you still can not count on the kref from remaining in | |
| 57 | * memory. Only use the return value if you want to see if the kref is now | |
| 58 | * gone, not present. | |
| 59 | */ | |
| 60 | static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref)) | |
| 61 | { | |
| 62 | WARN_ON(release == NULL); | |
| 63 | WARN_ON(release == (void (*)(struct kref *))kfree); | |
| 64 | ||
| 65 | if (atomic_dec_and_test(&kref->refcount)) { | |
| 66 | release(kref); | |
| 67 | return 1; | |
| 68 | } | |
| 69 | return 0; | |
| 70 | } | |
| 71 | ||
| 72 | ||
| 73 | /** | |
| 74 | * kref_sub - subtract a number of refcounts for object. | |
| 75 | * @kref: object. | |
| 76 | * @count: Number of recounts to subtract. | |
| 77 | * @release: pointer to the function that will clean up the object when the | |
| 78 | * last reference to the object is released. | |
| 79 | * This pointer is required, and it is not acceptable to pass kfree | |
| 80 | * in as this function. | |
| 81 | * | |
| 82 | * Subtract @count from the refcount, and if 0, call release(). | |
| 83 | * Return 1 if the object was removed, otherwise return 0. Beware, if this | |
| 84 | * function returns 0, you still can not count on the kref from remaining in | |
| 85 | * memory. Only use the return value if you want to see if the kref is now | |
| 86 | * gone, not present. | |
| 87 | */ | |
| 88 | static inline int kref_sub(struct kref *kref, unsigned int count, | |
| 89 | void (*release)(struct kref *kref)) | |
| 90 | { | |
| 91 | WARN_ON(release == NULL); | |
| 92 | WARN_ON(release == (void (*)(struct kref *))kfree); | |
| 1da177e4 | 93 | |
| 4af679cd PZ |
94 | if (atomic_sub_and_test((int) count, &kref->refcount)) { |
| 95 | release(kref); | |
| 96 | return 1; | |
| 97 | } | |
| 98 | return 0; | |
| 99 | } | |
| 1da177e4 | 100 | #endif /* _KREF_H_ */ |