1/*
2 * net/tipc/ref.c: TIPC object registry code
3 *
4 * Copyright (c) 1991-2006, Ericsson AB
5 * Copyright (c) 2004-2005, Wind River Systems
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the names of the copyright holders nor the names of its
17 *    contributors may be used to endorse or promote products derived from
18 *    this software without specific prior written permission.
19 *
20 * Alternatively, this software may be distributed under the terms of the
21 * GNU General Public License ("GPL") version 2 as published by the Free
22 * Software Foundation.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
25 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
28 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
29 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
30 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
31 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
32 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
33 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
34 * POSSIBILITY OF SUCH DAMAGE.
35 */
36
37#include "core.h"
38#include "ref.h"
39#include "port.h"
40#include "subscr.h"
41#include "name_distr.h"
42#include "name_table.h"
43#include "config.h"
44#include "discover.h"
45#include "bearer.h"
46#include "node.h"
47#include "bcast.h"
48
49
50struct ref_table tipc_ref_table = { NULL };
51
52static DEFINE_RWLOCK(ref_table_lock);
53
54/**
55 * tipc_ref_table_init - create reference table for objects
56 */
57
58int tipc_ref_table_init(u32 requested_size, u32 start)
59{
60	struct reference *table;
61	u32 sz = 1 << 4;
62	u32 index_mask;
63	int i;
64
65	while (sz < requested_size) {
66		sz <<= 1;
67	}
68	table = vmalloc(sz * sizeof(*table));
69	if (table == NULL)
70		return -ENOMEM;
71
72	write_lock_bh(&ref_table_lock);
73	index_mask = sz - 1;
74	for (i = sz - 1; i >= 0; i--) {
75		table[i].object = NULL;
76		spin_lock_init(&table[i].lock);
77		table[i].data.next_plus_upper = (start & ~index_mask) + i - 1;
78	}
79	tipc_ref_table.entries = table;
80	tipc_ref_table.index_mask = index_mask;
81	tipc_ref_table.first_free = sz - 1;
82	tipc_ref_table.last_free = 1;
83	write_unlock_bh(&ref_table_lock);
84	return TIPC_OK;
85}
86
87/**
88 * tipc_ref_table_stop - destroy reference table for objects
89 */
90
91void tipc_ref_table_stop(void)
92{
93	if (!tipc_ref_table.entries)
94		return;
95
96	vfree(tipc_ref_table.entries);
97	tipc_ref_table.entries = NULL;
98}
99
100/**
101 * tipc_ref_acquire - create reference to an object
102 *
103 * Return a unique reference value which can be translated back to the pointer
104 * 'object' at a later time.  Also, pass back a pointer to the lock protecting
105 * the object, but without locking it.
106 */
107
108u32 tipc_ref_acquire(void *object, spinlock_t **lock)
109{
110	struct reference *entry;
111	u32 index;
112	u32 index_mask;
113	u32 next_plus_upper;
114	u32 reference = 0;
115
116	if (!object) {
117		err("Attempt to acquire reference to non-existent object\n");
118		return 0;
119	}
120	if (!tipc_ref_table.entries) {
121		err("Reference table not found during acquisition attempt\n");
122		return 0;
123	}
124
125	write_lock_bh(&ref_table_lock);
126	if (tipc_ref_table.first_free) {
127		index = tipc_ref_table.first_free;
128		entry = &(tipc_ref_table.entries[index]);
129		index_mask = tipc_ref_table.index_mask;
130		/* take lock in case a previous user of entry still holds it */
131		spin_lock_bh(&entry->lock);
132		next_plus_upper = entry->data.next_plus_upper;
133		tipc_ref_table.first_free = next_plus_upper & index_mask;
134		reference = (next_plus_upper & ~index_mask) + index;
135		entry->data.reference = reference;
136		entry->object = object;
137		if (lock != 0)
138			*lock = &entry->lock;
139		spin_unlock_bh(&entry->lock);
140	}
141	write_unlock_bh(&ref_table_lock);
142	return reference;
143}
144
145/**
146 * tipc_ref_discard - invalidate references to an object
147 *
148 * Disallow future references to an object and free up the entry for re-use.
149 * Note: The entry's spin_lock may still be busy after discard
150 */
151
152void tipc_ref_discard(u32 ref)
153{
154	struct reference *entry;
155	u32 index;
156	u32 index_mask;
157
158	if (!ref) {
159		err("Attempt to discard reference 0\n");
160		return;
161	}
162	if (!tipc_ref_table.entries) {
163		err("Reference table not found during discard attempt\n");
164		return;
165	}
166
167	write_lock_bh(&ref_table_lock);
168	index_mask = tipc_ref_table.index_mask;
169	index = ref & index_mask;
170	entry = &(tipc_ref_table.entries[index]);
171
172	if (!entry->object) {
173		err("Attempt to discard reference to non-existent object\n");
174		goto exit;
175	}
176	if (entry->data.reference != ref) {
177		err("Attempt to discard non-existent reference\n");
178		goto exit;
179	}
180
181	/* mark entry as unused */
182	entry->object = NULL;
183	if (tipc_ref_table.first_free == 0)
184		tipc_ref_table.first_free = index;
185	else
186		tipc_ref_table.entries[tipc_ref_table.last_free].data.next_plus_upper
187			|= index;
188	tipc_ref_table.last_free = index;
189
190	/* increment upper bits of entry to invalidate subsequent references */
191	entry->data.next_plus_upper = (ref & ~index_mask) + (index_mask + 1);
192exit:
193	write_unlock_bh(&ref_table_lock);
194}
195