| 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 |
| 42 | struct krwobj { |
| 43 | krwlock_t ro_lock; |
| 44 | u_int ro_magic; |
| 45 | u_int ro_refcnt; |
| 46 | }; |
| 47 | |
| 48 | static int rw_obj_ctor(void *, void *, int); |
| 49 | |
| 50 | static pool_cache_t rw_obj_cache __read_mostly; |
| 51 | |
| 52 | /* |
| 53 | * rw_obj_init: |
| 54 | * |
| 55 | * Initialize the rw object store. |
| 56 | */ |
| 57 | void |
| 58 | rw_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 | */ |
| 71 | static int |
| 72 | rw_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 | */ |
| 86 | krwlock_t * |
| 87 | rw_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 | */ |
| 104 | void |
| 105 | rw_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 | */ |
| 121 | bool |
| 122 | rw_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 | |