2 * net/tipc/ref.c: TIPC object registry code
4 * Copyright (c) 1991-2006, Ericsson AB
5 * Copyright (c) 2004-2007, Wind River Systems
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41 #include "name_distr.h"
42 #include "name_table.h"
50 * struct reference - TIPC object reference entry
51 * @object: pointer to object associated with reference entry
52 * @lock: spinlock controlling access to object
53 * @data: reference value for object (combines instance & array index info)
66 * struct tipc_ref_table - table of TIPC object reference entries
67 * @entries: pointer to array of reference entries
68 * @capacity: array index of first unusable entry
69 * @init_point: array index of first uninitialized entry
70 * @first_free: array index of first unused object reference entry
71 * @last_free: array index of last unused object reference entry
72 * @index_mask: bitmask for array index portion of reference values
73 * @start_mask: initial value for instance value portion of reference values
77 struct reference *entries;
87 * Object reference table consists of 2**N entries.
89 * State Object ptr Reference
90 * ----- ---------- ---------
91 * In use non-NULL XXXX|own index
92 * (XXXX changes each time entry is acquired)
93 * Free NULL YYYY|next free index
94 * (YYYY is one more than last used XXXX)
95 * Uninitialized NULL 0
97 * Entry 0 is not used; this allows index 0 to denote the end of the free list.
99 * Note that a reference value of 0 does not necessarily indicate that an
100 * entry is uninitialized, since the last entry in the free list could also
101 * have a reference value of 0 (although this is unlikely).
104 static struct ref_table tipc_ref_table = { NULL };
106 static DEFINE_RWLOCK(ref_table_lock);
109 * tipc_ref_table_init - create reference table for objects
112 int tipc_ref_table_init(u32 requested_size, u32 start)
114 struct reference *table;
117 /* account for unused entry, then round up size to a power of 2 */
120 for (actual_size = 16; actual_size < requested_size; actual_size <<= 1)
123 /* allocate table & mark all entries as uninitialized */
125 table = __vmalloc(actual_size * sizeof(struct reference),
126 GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, PAGE_KERNEL);
130 tipc_ref_table.entries = table;
131 tipc_ref_table.capacity = requested_size;
132 tipc_ref_table.init_point = 1;
133 tipc_ref_table.first_free = 0;
134 tipc_ref_table.last_free = 0;
135 tipc_ref_table.index_mask = actual_size - 1;
136 tipc_ref_table.start_mask = start & ~tipc_ref_table.index_mask;
142 * tipc_ref_table_stop - destroy reference table for objects
145 void tipc_ref_table_stop(void)
147 if (!tipc_ref_table.entries)
150 vfree(tipc_ref_table.entries);
151 tipc_ref_table.entries = NULL;
155 * tipc_ref_acquire - create reference to an object
157 * Return a unique reference value which can be translated back to the pointer
158 * 'object' at a later time. Also, pass back a pointer to the lock protecting
159 * the object, but without locking it.
162 u32 tipc_ref_acquire(void *object, spinlock_t **lock)
164 struct reference *entry;
171 err("Attempt to acquire reference to non-existent object\n");
174 if (!tipc_ref_table.entries) {
175 err("Reference table not found during acquisition attempt\n");
179 /* take a free entry, if available; otherwise initialize a new entry */
181 write_lock_bh(&ref_table_lock);
182 if (tipc_ref_table.first_free) {
183 index = tipc_ref_table.first_free;
184 entry = &(tipc_ref_table.entries[index]);
185 index_mask = tipc_ref_table.index_mask;
186 /* take lock in case a previous user of entry still holds it */
187 spin_lock_bh(&entry->lock);
188 next_plus_upper = entry->data.next_plus_upper;
189 tipc_ref_table.first_free = next_plus_upper & index_mask;
190 reference = (next_plus_upper & ~index_mask) + index;
191 entry->data.reference = reference;
192 entry->object = object;
193 spin_unlock_bh(&entry->lock);
194 *lock = &entry->lock;
196 else if (tipc_ref_table.init_point < tipc_ref_table.capacity) {
197 index = tipc_ref_table.init_point++;
198 entry = &(tipc_ref_table.entries[index]);
199 spin_lock_init(&entry->lock);
200 reference = tipc_ref_table.start_mask + index;
201 entry->data.reference = reference;
202 entry->object = object;
203 *lock = &entry->lock;
208 write_unlock_bh(&ref_table_lock);
214 * tipc_ref_discard - invalidate references to an object
216 * Disallow future references to an object and free up the entry for re-use.
217 * Note: The entry's spin_lock may still be busy after discard
220 void tipc_ref_discard(u32 ref)
222 struct reference *entry;
226 if (!tipc_ref_table.entries) {
227 err("Reference table not found during discard attempt\n");
231 index_mask = tipc_ref_table.index_mask;
232 index = ref & index_mask;
233 entry = &(tipc_ref_table.entries[index]);
235 write_lock_bh(&ref_table_lock);
237 if (!entry->object) {
238 err("Attempt to discard reference to non-existent object\n");
241 if (entry->data.reference != ref) {
242 err("Attempt to discard non-existent reference\n");
247 * mark entry as unused; increment upper bits of entry's data field
248 * to invalidate any subsequent references
251 entry->object = NULL;
252 entry->data.next_plus_upper = (ref & ~index_mask) + (index_mask + 1);
254 /* append entry to free entry list */
256 if (tipc_ref_table.first_free == 0)
257 tipc_ref_table.first_free = index;
259 tipc_ref_table.entries[tipc_ref_table.last_free].
260 data.next_plus_upper |= index;
261 tipc_ref_table.last_free = index;
264 write_unlock_bh(&ref_table_lock);
268 * tipc_ref_lock - lock referenced object and return pointer to it
271 void *tipc_ref_lock(u32 ref)
273 if (likely(tipc_ref_table.entries)) {
276 r = &tipc_ref_table.entries[ref & tipc_ref_table.index_mask];
278 if (likely(r->data.reference != 0)) {
279 spin_lock_bh(&r->lock);
280 if (likely((r->data.reference == ref) && (r->object)))
282 spin_unlock_bh(&r->lock);
289 * tipc_ref_unlock - unlock referenced object
292 void tipc_ref_unlock(u32 ref)
294 if (likely(tipc_ref_table.entries)) {
297 r = &tipc_ref_table.entries[ref & tipc_ref_table.index_mask];
299 if (likely((r->data.reference == ref) && (r->object)))
300 spin_unlock_bh(&r->lock);
302 err("tipc_ref_unlock() invoked using "
303 "invalid reference\n");
308 * tipc_ref_deref - return pointer referenced object (without locking it)
311 void *tipc_ref_deref(u32 ref)
313 if (likely(tipc_ref_table.entries)) {
316 r = &tipc_ref_table.entries[ref & tipc_ref_table.index_mask];
317 if (likely(r->data.reference == ref))