1/* $NetBSD: kern_rwlock_obj.c,v 1.3 2011/05/13 22:16:43 rmind Exp $ */
2
3/*-
4 * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Andrew Doran.
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#include <sys/cdefs.h>
33__KERNEL_RCSID(0, "$NetBSD: kern_rwlock_obj.c,v 1.3 2011/05/13 22:16:43 rmind Exp $");
34
35#include <sys/param.h>
36#include <sys/atomic.h>
37#include <sys/pool.h>
38#include <sys/rwlock.h>
39
40/* Mutex cache */
41#define RW_OBJ_MAGIC 0x85d3c85d
42struct krwobj {
43 krwlock_t ro_lock;
44 u_int ro_magic;
45 u_int ro_refcnt;
46};
47
48static int rw_obj_ctor(void *, void *, int);
49
50static pool_cache_t rw_obj_cache __read_mostly;
51
52/*
53 * rw_obj_init:
54 *
55 * Initialize the rw object store.
56 */
57void
58rw_obj_init(void)
59{
60
61 rw_obj_cache = pool_cache_init(sizeof(struct krwobj),
62 coherency_unit, 0, 0, "rwlock", NULL, IPL_NONE, rw_obj_ctor,
63 NULL, NULL);
64}
65
66/*
67 * rw_obj_ctor:
68 *
69 * Initialize a new lock for the cache.
70 */
71static int
72rw_obj_ctor(void *arg, void *obj, int flags)
73{
74 struct krwobj * ro = obj;
75
76 ro->ro_magic = RW_OBJ_MAGIC;
77
78 return 0;
79}
80
81/*
82 * rw_obj_alloc:
83 *
84 * Allocate a single lock object.
85 */
86krwlock_t *
87rw_obj_alloc(void)
88{
89 struct krwobj *ro;
90
91 ro = pool_cache_get(rw_obj_cache, PR_WAITOK);
92 rw_init(&ro->ro_lock);
93 ro->ro_refcnt = 1;
94
95 return (krwlock_t *)ro;
96}
97
98/*
99 * rw_obj_hold:
100 *
101 * Add a single reference to a lock object. A reference to the object
102 * must already be held, and must be held across this call.
103 */
104void
105rw_obj_hold(krwlock_t *lock)
106{
107 struct krwobj *ro = (struct krwobj *)lock;
108
109 KASSERT(ro->ro_magic == RW_OBJ_MAGIC);
110 KASSERT(ro->ro_refcnt > 0);
111
112 atomic_inc_uint(&ro->ro_refcnt);
113}
114
115/*
116 * rw_obj_free:
117 *
118 * Drop a reference from a lock object. If the last reference is being
119 * dropped, free the object and return true. Otherwise, return false.
120 */
121bool
122rw_obj_free(krwlock_t *lock)
123{
124 struct krwobj *ro = (struct krwobj *)lock;
125
126 KASSERT(ro->ro_magic == RW_OBJ_MAGIC);
127 KASSERT(ro->ro_refcnt > 0);
128
129 if (atomic_dec_uint_nv(&ro->ro_refcnt) > 0) {
130 return false;
131 }
132 rw_destroy(&ro->ro_lock);
133 pool_cache_put(rw_obj_cache, ro);
134 return true;
135}
136