1/* $NetBSD: kern_mutex_obj.c,v 1.5 2011/09/27 01:02:38 jym Exp $ */
2
3/*-
4 * Copyright (c) 2008 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_mutex_obj.c,v 1.5 2011/09/27 01:02:38 jym Exp $");
34
35#include <sys/param.h>
36#include <sys/atomic.h>
37#include <sys/mutex.h>
38#include <sys/pool.h>
39
40/* Mutex cache */
41#define MUTEX_OBJ_MAGIC 0x5aa3c85d
42struct kmutexobj {
43 kmutex_t mo_lock;
44 u_int mo_magic;
45 u_int mo_refcnt;
46};
47
48static int mutex_obj_ctor(void *, void *, int);
49
50static pool_cache_t mutex_obj_cache __read_mostly;
51
52/*
53 * mutex_obj_init:
54 *
55 * Initialize the mutex object store.
56 */
57void
58mutex_obj_init(void)
59{
60
61 mutex_obj_cache = pool_cache_init(sizeof(struct kmutexobj),
62 coherency_unit, 0, 0, "mutex", NULL, IPL_NONE, mutex_obj_ctor,
63 NULL, NULL);
64}
65
66/*
67 * mutex_obj_ctor:
68 *
69 * Initialize a new lock for the cache.
70 */
71static int
72mutex_obj_ctor(void *arg, void *obj, int flags)
73{
74 struct kmutexobj * mo = obj;
75
76 mo->mo_magic = MUTEX_OBJ_MAGIC;
77
78 return 0;
79}
80
81/*
82 * mutex_obj_alloc:
83 *
84 * Allocate a single lock object.
85 */
86kmutex_t *
87mutex_obj_alloc(kmutex_type_t type, int ipl)
88{
89 struct kmutexobj *mo;
90
91 mo = pool_cache_get(mutex_obj_cache, PR_WAITOK);
92 mutex_init(&mo->mo_lock, type, ipl);
93 mo->mo_refcnt = 1;
94
95 return (kmutex_t *)mo;
96}
97
98/*
99 * mutex_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
105mutex_obj_hold(kmutex_t *lock)
106{
107 struct kmutexobj *mo = (struct kmutexobj *)lock;
108
109 KASSERTMSG(mo->mo_magic == MUTEX_OBJ_MAGIC,
110 "%s: lock %p: mo->mo_magic (%#x) != MUTEX_OBJ_MAGIC (%#x)",
111 __func__, mo, mo->mo_magic, MUTEX_OBJ_MAGIC);
112 KASSERTMSG(mo->mo_refcnt > 0,
113 "%s: lock %p: mo->mo_refcnt (%#x) == 0",
114 __func__, mo, mo->mo_refcnt);
115
116 atomic_inc_uint(&mo->mo_refcnt);
117}
118
119/*
120 * mutex_obj_free:
121 *
122 * Drop a reference from a lock object. If the last reference is being
123 * dropped, free the object and return true. Otherwise, return false.
124 */
125bool
126mutex_obj_free(kmutex_t *lock)
127{
128 struct kmutexobj *mo = (struct kmutexobj *)lock;
129
130 KASSERTMSG(mo->mo_magic == MUTEX_OBJ_MAGIC,
131 "%s: lock %p: mo->mo_magic (%#x) != MUTEX_OBJ_MAGIC (%#x)",
132 __func__, mo, mo->mo_magic, MUTEX_OBJ_MAGIC);
133 KASSERTMSG(mo->mo_refcnt > 0,
134 "%s: lock %p: mo->mo_refcnt (%#x) == 0",
135 __func__, mo, mo->mo_refcnt);
136
137 if (atomic_dec_uint_nv(&mo->mo_refcnt) > 0) {
138 return false;
139 }
140 mutex_destroy(&mo->mo_lock);
141 pool_cache_put(mutex_obj_cache, mo);
142 return true;
143}
144