2 * net/tipc/ref.c: TIPC object registry code
4 * Copyright (c) 1991-2006, Ericsson AB
5 * Copyright (c) 2004-2007, Wind River Systems
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions are met:
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.
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.
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.
41 * struct reference - TIPC object reference entry
42 * @object: pointer to object associated with reference entry
43 * @lock: spinlock controlling access to object
44 * @ref: reference value for object (combines instance & array index info)
53 * struct tipc_ref_table - table of TIPC object reference entries
54 * @entries: pointer to array of reference entries
55 * @capacity: array index of first unusable entry
56 * @init_point: array index of first uninitialized entry
57 * @first_free: array index of first unused object reference entry
58 * @last_free: array index of last unused object reference entry
59 * @index_mask: bitmask for array index portion of reference values
60 * @start_mask: initial value for instance value portion of reference values
63 struct reference *entries;
73 * Object reference table consists of 2**N entries.
75 * State Object ptr Reference
76 * ----- ---------- ---------
77 * In use non-NULL XXXX|own index
78 * (XXXX changes each time entry is acquired)
79 * Free NULL YYYY|next free index
80 * (YYYY is one more than last used XXXX)
81 * Uninitialized NULL 0
83 * Entry 0 is not used; this allows index 0 to denote the end of the free list.
85 * Note that a reference value of 0 does not necessarily indicate that an
86 * entry is uninitialized, since the last entry in the free list could also
87 * have a reference value of 0 (although this is unlikely).
90 static struct ref_table tipc_ref_table;
92 static DEFINE_SPINLOCK(ref_table_lock);
95 * tipc_ref_table_init - create reference table for objects
97 int tipc_ref_table_init(u32 requested_size, u32 start)
99 struct reference *table;
102 /* account for unused entry, then round up size to a power of 2 */
105 for (actual_size = 16; actual_size < requested_size; actual_size <<= 1)
108 /* allocate table & mark all entries as uninitialized */
109 table = vzalloc(actual_size * sizeof(struct reference));
113 tipc_ref_table.entries = table;
114 tipc_ref_table.capacity = requested_size;
115 tipc_ref_table.init_point = 1;
116 tipc_ref_table.first_free = 0;
117 tipc_ref_table.last_free = 0;
118 tipc_ref_table.index_mask = actual_size - 1;
119 tipc_ref_table.start_mask = start & ~tipc_ref_table.index_mask;
125 * tipc_ref_table_stop - destroy reference table for objects
127 void tipc_ref_table_stop(void)
129 vfree(tipc_ref_table.entries);
130 tipc_ref_table.entries = NULL;
134 * tipc_ref_acquire - create reference to an object
136 * Register an object pointer in reference table and lock the object.
137 * Returns a unique reference value that is used from then on to retrieve the
138 * object pointer, or to determine that the object has been deregistered.
140 * Note: The object is returned in the locked state so that the caller can
141 * register a partially initialized object, without running the risk that
142 * the object will be accessed before initialization is complete.
144 u32 tipc_ref_acquire(void *object, spinlock_t **lock)
150 struct reference *entry = NULL;
153 pr_err("Attempt to acquire ref. to non-existent obj\n");
156 if (!tipc_ref_table.entries) {
157 pr_err("Ref. table not found in acquisition attempt\n");
161 /* take a free entry, if available; otherwise initialize a new entry */
162 spin_lock_bh(&ref_table_lock);
163 if (tipc_ref_table.first_free) {
164 index = tipc_ref_table.first_free;
165 entry = &(tipc_ref_table.entries[index]);
166 index_mask = tipc_ref_table.index_mask;
167 next_plus_upper = entry->ref;
168 tipc_ref_table.first_free = next_plus_upper & index_mask;
169 ref = (next_plus_upper & ~index_mask) + index;
170 } else if (tipc_ref_table.init_point < tipc_ref_table.capacity) {
171 index = tipc_ref_table.init_point++;
172 entry = &(tipc_ref_table.entries[index]);
173 spin_lock_init(&entry->lock);
174 ref = tipc_ref_table.start_mask + index;
178 spin_unlock_bh(&ref_table_lock);
181 * Grab the lock so no one else can modify this entry
182 * While we assign its ref value & object pointer
185 spin_lock_bh(&entry->lock);
187 entry->object = object;
188 *lock = &entry->lock;
190 * keep it locked, the caller is responsible
191 * for unlocking this when they're done with it
199 * tipc_ref_discard - invalidate references to an object
201 * Disallow future references to an object and free up the entry for re-use.
202 * Note: The entry's spin_lock may still be busy after discard
204 void tipc_ref_discard(u32 ref)
206 struct reference *entry;
210 if (!tipc_ref_table.entries) {
211 pr_err("Ref. table not found during discard attempt\n");
215 index_mask = tipc_ref_table.index_mask;
216 index = ref & index_mask;
217 entry = &(tipc_ref_table.entries[index]);
219 spin_lock_bh(&ref_table_lock);
221 if (!entry->object) {
222 pr_err("Attempt to discard ref. to non-existent obj\n");
225 if (entry->ref != ref) {
226 pr_err("Attempt to discard non-existent reference\n");
231 * mark entry as unused; increment instance part of entry's reference
232 * to invalidate any subsequent references
234 entry->object = NULL;
235 entry->ref = (ref & ~index_mask) + (index_mask + 1);
237 /* append entry to free entry list */
238 if (tipc_ref_table.first_free == 0)
239 tipc_ref_table.first_free = index;
241 tipc_ref_table.entries[tipc_ref_table.last_free].ref |= index;
242 tipc_ref_table.last_free = index;
245 spin_unlock_bh(&ref_table_lock);
249 * tipc_ref_lock - lock referenced object and return pointer to it
251 void *tipc_ref_lock(u32 ref)
253 if (likely(tipc_ref_table.entries)) {
254 struct reference *entry;
256 entry = &tipc_ref_table.entries[ref &
257 tipc_ref_table.index_mask];
258 if (likely(entry->ref != 0)) {
259 spin_lock_bh(&entry->lock);
260 if (likely((entry->ref == ref) && (entry->object)))
261 return entry->object;
262 spin_unlock_bh(&entry->lock);