1 /* $NetBSD: kern_mutex_obj.c,v 1.2 2010/03/31 19:59:39 ad 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 1.2 2010/03/31 19:59:39 ad 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 42 struct kmutexobj { 43 kmutex_t mo_lock; 44 u_int mo_magic; 45 u_int mo_refcnt; 46 }; 47 48 static int mutex_obj_ctor(void *, void *, int); 49 50 static pool_cache_t mutex_obj_cache; 51 52 /* 53 * mutex_obj_init: 54 * 55 * Initialize the mutex object store. 56 */ 57 void 58 mutex_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 */ 71 static int 72 mutex_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 */ 86 kmutex_t * 87 mutex_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 */ 104 void 105 mutex_obj_hold(kmutex_t *lock) 106 { 107 struct kmutexobj *mo = (struct kmutexobj *)lock; 108 109 KASSERT(mo->mo_magic == MUTEX_OBJ_MAGIC); 110 KASSERT(mo->mo_refcnt > 0); 111 112 atomic_inc_uint(&mo->mo_refcnt); 113 } 114 115 /* 116 * mutex_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 */ 121 bool 122 mutex_obj_free(kmutex_t *lock) 123 { 124 struct kmutexobj *mo = (struct kmutexobj *)lock; 125 126 KASSERT(mo->mo_magic == MUTEX_OBJ_MAGIC); 127 KASSERT(mo->mo_refcnt > 0); 128 129 if (atomic_dec_uint_nv(&mo->mo_refcnt) > 0) { 130 return false; 131 } 132 mutex_destroy(&mo->mo_lock); 133 pool_cache_put(mutex_obj_cache, mo); 134 return true; 135 } 136