1 | /* $NetBSD: kref.h,v 1.4 2014/07/16 20:59:58 riastradh Exp $ */ |
2 | |
3 | /*- |
4 | * Copyright (c) 2013 The NetBSD Foundation, Inc. |
5 | * All rights reserved. |
6 | * |
7 | * This code is derived from software contributed to The NetBSD Foundation |
8 | * by Taylor R. Campbell. |
9 | * |
10 | * Redistribution and use in source and binary forms, with or without |
11 | * modification, are permitted provided that the following conditions |
12 | * are met: |
13 | * 1. Redistributions of source code must retain the above copyright |
14 | * notice, this list of conditions and the following disclaimer. |
15 | * 2. Redistributions in binary form must reproduce the above copyright |
16 | * notice, this list of conditions and the following disclaimer in the |
17 | * documentation and/or other materials provided with the distribution. |
18 | * |
19 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
20 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
21 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
22 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
23 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
24 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
25 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
26 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
27 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
28 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
29 | * POSSIBILITY OF SUCH DAMAGE. |
30 | */ |
31 | |
32 | #ifndef _LINUX_KREF_H_ |
33 | #define _LINUX_KREF_H_ |
34 | |
35 | #include <sys/types.h> |
36 | #include <sys/atomic.h> |
37 | #include <sys/systm.h> |
38 | |
39 | #include <linux/mutex.h> |
40 | |
41 | struct kref { |
42 | unsigned int kr_count; |
43 | }; |
44 | |
45 | static inline void |
46 | kref_init(struct kref *kref) |
47 | { |
48 | kref->kr_count = 1; |
49 | } |
50 | |
51 | static inline void |
52 | kref_get(struct kref *kref) |
53 | { |
54 | const unsigned int count __unused = |
55 | atomic_inc_uint_nv(&kref->kr_count); |
56 | |
57 | KASSERTMSG((count > 1), "getting released kref" ); |
58 | } |
59 | |
60 | static inline bool |
61 | kref_get_unless_zero(struct kref *kref) |
62 | { |
63 | unsigned count; |
64 | |
65 | do { |
66 | count = kref->kr_count; |
67 | if ((count == 0) || (count == UINT_MAX)) |
68 | return false; |
69 | } while (atomic_cas_uint(&kref->kr_count, count, (count + 1)) != |
70 | count); |
71 | |
72 | return true; |
73 | } |
74 | |
75 | static inline int |
76 | kref_sub(struct kref *kref, unsigned int count, void (*release)(struct kref *)) |
77 | { |
78 | unsigned int old, new; |
79 | |
80 | do { |
81 | old = kref->kr_count; |
82 | KASSERTMSG((count <= old), "overreleasing kref: %u - %u" , |
83 | old, count); |
84 | new = (old - count); |
85 | } while (atomic_cas_uint(&kref->kr_count, old, new) != old); |
86 | |
87 | if (new == 0) { |
88 | (*release)(kref); |
89 | return 1; |
90 | } |
91 | |
92 | return 0; |
93 | } |
94 | |
95 | static inline int |
96 | kref_put(struct kref *kref, void (*release)(struct kref *)) |
97 | { |
98 | |
99 | return kref_sub(kref, 1, release); |
100 | } |
101 | |
102 | static inline int |
103 | kref_put_mutex(struct kref *kref, void (*release)(struct kref *), |
104 | struct mutex *interlock) |
105 | { |
106 | unsigned int old, new; |
107 | |
108 | do { |
109 | old = kref->kr_count; |
110 | KASSERT(old > 0); |
111 | if (old == 1) { |
112 | mutex_lock(interlock); |
113 | if (atomic_add_int_nv(&kref->kr_count, -1) == 0) { |
114 | (*release)(kref); |
115 | return 1; |
116 | } |
117 | mutex_unlock(interlock); |
118 | return 0; |
119 | } |
120 | new = (old - 1); |
121 | } while (atomic_cas_uint(&kref->kr_count, old, new) != old); |
122 | |
123 | return 0; |
124 | } |
125 | |
126 | /* |
127 | * Not native to Linux. Mostly used for assertions... |
128 | */ |
129 | |
130 | static inline bool |
131 | kref_referenced_p(struct kref *kref) |
132 | { |
133 | |
134 | return (0 < kref->kr_count); |
135 | } |
136 | |
137 | static inline bool |
138 | kref_exclusive_p(struct kref *kref) |
139 | { |
140 | |
141 | KASSERT(0 < kref->kr_count); |
142 | return (kref->kr_count == 1); |
143 | } |
144 | |
145 | #endif /* _LINUX_KREF_H_ */ |
146 | |