| 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 | |