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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 /*
     22  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
     23  * Use is subject to license terms.
     24  */
     25 
     26 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     27 
     28 #include <sys/zfs_context.h>
     29 #include <sys/refcount.h>
     30 
     31 #if defined(DEBUG) || !defined(_KERNEL)
     32 
     33 #ifdef _KERNEL
     34 int reference_tracking_enable = FALSE; /* runs out of memory too easily */
     35 #else
     36 int reference_tracking_enable = TRUE;
     37 #endif
     38 int reference_history = 4; /* tunable */
     39 
     40 static kmem_cache_t *reference_cache;
     41 static kmem_cache_t *reference_history_cache;
     42 
     43 void
     44 refcount_init(void)
     45 {
     46 	reference_cache = kmem_cache_create("reference_cache",
     47 	    sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
     48 
     49 	reference_history_cache = kmem_cache_create("reference_history_cache",
     50 	    sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
     51 }
     52 
     53 void
     54 refcount_fini(void)
     55 {
     56 	kmem_cache_destroy(reference_cache);
     57 	kmem_cache_destroy(reference_history_cache);
     58 }
     59 
     60 void
     61 refcount_create(refcount_t *rc)
     62 {
     63 	mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL);
     64 	list_create(&rc->rc_list, sizeof (reference_t),
     65 	    offsetof(reference_t, ref_link));
     66 	list_create(&rc->rc_removed, sizeof (reference_t),
     67 	    offsetof(reference_t, ref_link));
     68 	rc->rc_count = 0;
     69 	rc->rc_removed_count = 0;
     70 }
     71 
     72 void
     73 refcount_destroy_many(refcount_t *rc, uint64_t number)
     74 {
     75 	reference_t *ref;
     76 
     77 	ASSERT(rc->rc_count == number);
     78 	while (ref = list_head(&rc->rc_list)) {
     79 		list_remove(&rc->rc_list, ref);
     80 		kmem_cache_free(reference_cache, ref);
     81 	}
     82 	list_destroy(&rc->rc_list);
     83 
     84 	while (ref = list_head(&rc->rc_removed)) {
     85 		list_remove(&rc->rc_removed, ref);
     86 		kmem_cache_free(reference_history_cache, ref->ref_removed);
     87 		kmem_cache_free(reference_cache, ref);
     88 	}
     89 	list_destroy(&rc->rc_removed);
     90 	mutex_destroy(&rc->rc_mtx);
     91 }
     92 
     93 void
     94 refcount_destroy(refcount_t *rc)
     95 {
     96 	refcount_destroy_many(rc, 0);
     97 }
     98 
     99 int
    100 refcount_is_zero(refcount_t *rc)
    101 {
    102 	ASSERT(rc->rc_count >= 0);
    103 	return (rc->rc_count == 0);
    104 }
    105 
    106 int64_t
    107 refcount_count(refcount_t *rc)
    108 {
    109 	ASSERT(rc->rc_count >= 0);
    110 	return (rc->rc_count);
    111 }
    112 
    113 int64_t
    114 refcount_add_many(refcount_t *rc, uint64_t number, void *holder)
    115 {
    116 	reference_t *ref;
    117 	int64_t count;
    118 
    119 	if (reference_tracking_enable) {
    120 		ref = kmem_cache_alloc(reference_cache, KM_SLEEP);
    121 		ref->ref_holder = holder;
    122 		ref->ref_number = number;
    123 	}
    124 	mutex_enter(&rc->rc_mtx);
    125 	ASSERT(rc->rc_count >= 0);
    126 	if (reference_tracking_enable)
    127 		list_insert_head(&rc->rc_list, ref);
    128 	rc->rc_count += number;
    129 	count = rc->rc_count;
    130 	mutex_exit(&rc->rc_mtx);
    131 
    132 	return (count);
    133 }
    134 
    135 int64_t
    136 refcount_add(refcount_t *rc, void *holder)
    137 {
    138 	return (refcount_add_many(rc, 1, holder));
    139 }
    140 
    141 int64_t
    142 refcount_remove_many(refcount_t *rc, uint64_t number, void *holder)
    143 {
    144 	reference_t *ref;
    145 	int64_t count;
    146 
    147 	mutex_enter(&rc->rc_mtx);
    148 	ASSERT(rc->rc_count >= number);
    149 
    150 	if (!reference_tracking_enable) {
    151 		rc->rc_count -= number;
    152 		count = rc->rc_count;
    153 		mutex_exit(&rc->rc_mtx);
    154 		return (count);
    155 	}
    156 
    157 	for (ref = list_head(&rc->rc_list); ref;
    158 	    ref = list_next(&rc->rc_list, ref)) {
    159 		if (ref->ref_holder == holder && ref->ref_number == number) {
    160 			list_remove(&rc->rc_list, ref);
    161 			if (reference_history > 0) {
    162 				ref->ref_removed =
    163 				    kmem_cache_alloc(reference_history_cache,
    164 				    KM_SLEEP);
    165 				list_insert_head(&rc->rc_removed, ref);
    166 				rc->rc_removed_count++;
    167 				if (rc->rc_removed_count >= reference_history) {
    168 					ref = list_tail(&rc->rc_removed);
    169 					list_remove(&rc->rc_removed, ref);
    170 					kmem_cache_free(reference_history_cache,
    171 					    ref->ref_removed);
    172 					kmem_cache_free(reference_cache, ref);
    173 					rc->rc_removed_count--;
    174 				}
    175 			} else {
    176 				kmem_cache_free(reference_cache, ref);
    177 			}
    178 			rc->rc_count -= number;
    179 			count = rc->rc_count;
    180 			mutex_exit(&rc->rc_mtx);
    181 			return (count);
    182 		}
    183 	}
    184 	panic("No such hold %p on refcount %llx", holder,
    185 	    (u_longlong_t)(uintptr_t)rc);
    186 	return (-1);
    187 }
    188 
    189 int64_t
    190 refcount_remove(refcount_t *rc, void *holder)
    191 {
    192 	return (refcount_remove_many(rc, 1, holder));
    193 }
    194 
    195 #endif
    196