kern_mutex_obj.c revision 1.5.2.1
1 /* $NetBSD: kern_mutex_obj.c,v 1.5.2.1 2011/11/18 00:57:33 yamt 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 1.5.2.1 2011/11/18 00:57:33 yamt 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 __read_mostly; 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 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 */ 125 bool 126 mutex_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 /* 138 * if mo_refcnt is 1, no one except us have a reference to it and 139 * thus it's stable. 140 */ 141 if (mo->mo_refcnt != 1 && atomic_dec_uint_nv(&mo->mo_refcnt) > 0) { 142 return false; 143 } 144 mutex_destroy(&mo->mo_lock); 145 pool_cache_put(mutex_obj_cache, mo); 146 return true; 147 } 148 149 /* 150 * mutex_obj_pause: 151 * 152 * Pause until lock1 is available. 153 * Temporarily release and reacquire lock2. 154 * 155 * Typically used when we need to acquire locks in a reversed order 156 * and trylock failed. 157 */ 158 void 159 mutex_obj_pause(kmutex_t *lock1, kmutex_t *lock2) 160 { 161 162 KASSERT(mutex_owned(lock2)); 163 mutex_obj_hold(lock1); 164 mutex_exit(lock2); 165 mutex_enter(lock1); 166 mutex_exit(lock1); 167 mutex_obj_free(lock1); 168 mutex_enter(lock2); 169 } 170 171 /* 172 * mutex_obj_alloc_kernel_obj_lock: 173 * 174 * mutex_obj_alloc for kernel object lock. 175 * used for bootstrap. 176 */ 177 kmutex_t * 178 mutex_obj_alloc_kernel_obj_lock(kmutex_type_t type, int ipl) 179 { 180 static struct kmutexobj kernel_obj_lock; 181 struct kmutexobj *mo = &kernel_obj_lock; 182 183 KASSERT(mo->mo_refcnt == 0); 184 mutex_obj_ctor(NULL, mo, 0); 185 mutex_init(&mo->mo_lock, type, ipl); 186 mo->mo_refcnt = 1; 187 return (kmutex_t *)mo; 188 } 189 190
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