1 /* $NetBSD: kern_mutex_obj.c,v 1.15 2023/10/02 21:03:55 ad Exp $ */ 2 3 /*- 4 * Copyright (c) 2008, 2019, 2023 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 1.15 2023/10/02 21:03:55 ad Exp $"); 34 35 #include <sys/param.h> 36 #include <sys/atomic.h> 37 #include <sys/mutex.h> 38 #include <sys/kmem.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 uint8_t mo_pad[COHERENCY_UNIT - sizeof(kmutex_t) - 47 sizeof(u_int) * 2]; 48 }; 49 50 /* 51 * mutex_obj_alloc: 52 * 53 * Allocate a single lock object, waiting for memory if needed. 54 */ 55 kmutex_t * 56 mutex_obj_alloc(kmutex_type_t type, int ipl) 57 { 58 struct kmutexobj *mo; 59 60 mo = kmem_intr_alloc(sizeof(*mo), KM_SLEEP); 61 KASSERT(ALIGNED_POINTER(mo, coherency_unit)); 62 _mutex_init(&mo->mo_lock, type, ipl, 63 (uintptr_t)__builtin_return_address(0)); 64 mo->mo_magic = MUTEX_OBJ_MAGIC; 65 mo->mo_refcnt = 1; 66 67 return (kmutex_t *)mo; 68 } 69 70 /* 71 * mutex_obj_alloc: 72 * 73 * Allocate a single lock object, failing if no memory available. 74 */ 75 kmutex_t * 76 mutex_obj_tryalloc(kmutex_type_t type, int ipl) 77 { 78 struct kmutexobj *mo; 79 80 mo = kmem_intr_alloc(sizeof(*mo), KM_NOSLEEP); 81 KASSERT(ALIGNED_POINTER(mo, coherency_unit)); 82 if (__predict_true(mo != NULL)) { 83 _mutex_init(&mo->mo_lock, type, ipl, 84 (uintptr_t)__builtin_return_address(0)); 85 mo->mo_magic = MUTEX_OBJ_MAGIC; 86 mo->mo_refcnt = 1; 87 } 88 89 return (kmutex_t *)mo; 90 } 91 92 /* 93 * mutex_obj_hold: 94 * 95 * Add a single reference to a lock object. A reference to the object 96 * must already be held, and must be held across this call. 97 */ 98 void 99 mutex_obj_hold(kmutex_t *lock) 100 { 101 struct kmutexobj *mo = (struct kmutexobj *)lock; 102 103 KASSERTMSG(mo->mo_magic == MUTEX_OBJ_MAGIC, 104 "%s: lock %p: mo->mo_magic (%#x) != MUTEX_OBJ_MAGIC (%#x)", 105 __func__, mo, mo->mo_magic, MUTEX_OBJ_MAGIC); 106 KASSERTMSG(mo->mo_refcnt > 0, 107 "%s: lock %p: mo->mo_refcnt (%#x) == 0", 108 __func__, mo, mo->mo_refcnt); 109 110 atomic_inc_uint(&mo->mo_refcnt); 111 } 112 113 /* 114 * mutex_obj_free: 115 * 116 * Drop a reference from a lock object. If the last reference is being 117 * dropped, free the object and return true. Otherwise, return false. 118 */ 119 bool 120 mutex_obj_free(kmutex_t *lock) 121 { 122 struct kmutexobj *mo = (struct kmutexobj *)lock; 123 124 KASSERTMSG(mo->mo_magic == MUTEX_OBJ_MAGIC, 125 "%s: lock %p: mo->mo_magic (%#x) != MUTEX_OBJ_MAGIC (%#x)", 126 __func__, mo, mo->mo_magic, MUTEX_OBJ_MAGIC); 127 KASSERTMSG(mo->mo_refcnt > 0, 128 "%s: lock %p: mo->mo_refcnt (%#x) == 0", 129 __func__, mo, mo->mo_refcnt); 130 131 membar_release(); 132 if (atomic_dec_uint_nv(&mo->mo_refcnt) > 0) { 133 return false; 134 } 135 membar_acquire(); 136 mutex_destroy(&mo->mo_lock); 137 kmem_intr_free(mo, sizeof(*mo)); 138 return true; 139 } 140 141 /* 142 * mutex_obj_refcnt: 143 * 144 * Return the reference count on a lock object. 145 */ 146 u_int 147 mutex_obj_refcnt(kmutex_t *lock) 148 { 149 struct kmutexobj *mo = (struct kmutexobj *)lock; 150 151 return mo->mo_refcnt; 152 } 153