kref.h revision 1.4
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 41struct kref { 42 unsigned int kr_count; 43}; 44 45static inline void 46kref_init(struct kref *kref) 47{ 48 kref->kr_count = 1; 49} 50 51static inline void 52kref_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 60static inline bool 61kref_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 75static inline int 76kref_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 95static inline int 96kref_put(struct kref *kref, void (*release)(struct kref *)) 97{ 98 99 return kref_sub(kref, 1, release); 100} 101 102static inline int 103kref_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 130static inline bool 131kref_referenced_p(struct kref *kref) 132{ 133 134 return (0 < kref->kr_count); 135} 136 137static inline bool 138kref_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