Commit | Line | Data |
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55716d26 | 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
1da177e4 | 2 | /* |
932fb06b | 3 | * kref.h - library routines for handling generic reference counted objects |
1da177e4 LT |
4 | * |
5 | * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com> | |
6 | * Copyright (C) 2004 IBM Corp. | |
7 | * | |
8 | * based on kobject.h which was: | |
9 | * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org> | |
10 | * Copyright (C) 2002-2003 Open Source Development Labs | |
1da177e4 LT |
11 | */ |
12 | ||
13 | #ifndef _KREF_H_ | |
14 | #define _KREF_H_ | |
15 | ||
0a13cd1a | 16 | #include <linux/spinlock.h> |
10383aea | 17 | #include <linux/refcount.h> |
1da177e4 LT |
18 | |
19 | struct kref { | |
10383aea | 20 | refcount_t refcount; |
1da177e4 LT |
21 | }; |
22 | ||
10383aea | 23 | #define KREF_INIT(n) { .refcount = REFCOUNT_INIT(n), } |
1e24edca | 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 | { | |
10383aea | 31 | refcount_set(&kref->refcount, 1); |
4af679cd PZ |
32 | } |
33 | ||
10383aea | 34 | static inline unsigned int kref_read(const struct kref *kref) |
2c935bc5 | 35 | { |
10383aea | 36 | return refcount_read(&kref->refcount); |
2c935bc5 PZ |
37 | } |
38 | ||
4af679cd PZ |
39 | /** |
40 | * kref_get - increment refcount for object. | |
41 | * @kref: object. | |
42 | */ | |
43 | static inline void kref_get(struct kref *kref) | |
44 | { | |
10383aea | 45 | refcount_inc(&kref->refcount); |
4af679cd PZ |
46 | } |
47 | ||
48 | /** | |
bdfafc4f | 49 | * kref_put - decrement refcount for object. |
4af679cd PZ |
50 | * @kref: object. |
51 | * @release: pointer to the function that will clean up the object when the | |
52 | * last reference to the object is released. | |
53 | * This pointer is required, and it is not acceptable to pass kfree | |
186bddb2 | 54 | * in as this function. |
4af679cd | 55 | * |
bdfafc4f | 56 | * Decrement the refcount, and if 0, call release(). |
4af679cd PZ |
57 | * Return 1 if the object was removed, otherwise return 0. Beware, if this |
58 | * function returns 0, you still can not count on the kref from remaining in | |
59 | * memory. Only use the return value if you want to see if the kref is now | |
60 | * gone, not present. | |
61 | */ | |
bdfafc4f | 62 | static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref)) |
4af679cd | 63 | { |
10383aea | 64 | if (refcount_dec_and_test(&kref->refcount)) { |
4af679cd PZ |
65 | release(kref); |
66 | return 1; | |
67 | } | |
68 | return 0; | |
69 | } | |
70 | ||
8ad5db8a AV |
71 | static inline int kref_put_mutex(struct kref *kref, |
72 | void (*release)(struct kref *kref), | |
73 | struct mutex *lock) | |
74 | { | |
10383aea | 75 | if (refcount_dec_and_mutex_lock(&kref->refcount, lock)) { |
0a13cd1a PZ |
76 | release(kref); |
77 | return 1; | |
78 | } | |
79 | return 0; | |
80 | } | |
81 | ||
82 | static inline int kref_put_lock(struct kref *kref, | |
83 | void (*release)(struct kref *kref), | |
84 | spinlock_t *lock) | |
85 | { | |
10383aea | 86 | if (refcount_dec_and_lock(&kref->refcount, lock)) { |
8ad5db8a AV |
87 | release(kref); |
88 | return 1; | |
89 | } | |
90 | return 0; | |
91 | } | |
4b20db3d TH |
92 | |
93 | /** | |
94 | * kref_get_unless_zero - Increment refcount for object unless it is zero. | |
95 | * @kref: object. | |
96 | * | |
97 | * Return non-zero if the increment succeeded. Otherwise return 0. | |
98 | * | |
99 | * This function is intended to simplify locking around refcounting for | |
100 | * objects that can be looked up from a lookup structure, and which are | |
101 | * removed from that lookup structure in the object destructor. | |
102 | * Operations on such objects require at least a read lock around | |
103 | * lookup + kref_get, and a write lock around kref_put + remove from lookup | |
104 | * structure. Furthermore, RCU implementations become extremely tricky. | |
105 | * With a lookup followed by a kref_get_unless_zero *with return value check* | |
106 | * locking in the kref_put path can be deferred to the actual removal from | |
107 | * the lookup structure and RCU lookups become trivial. | |
108 | */ | |
109 | static inline int __must_check kref_get_unless_zero(struct kref *kref) | |
110 | { | |
10383aea | 111 | return refcount_inc_not_zero(&kref->refcount); |
4b20db3d | 112 | } |
1da177e4 | 113 | #endif /* _KREF_H_ */ |