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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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9 * modification, are permitted provided that the following conditions are met:
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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.
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25 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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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)
54 * struct tipc_ref_table - table of TIPC object reference entries
55 * @entries: pointer to array of reference entries
56 * @capacity: array index of first unusable entry
57 * @init_point: array index of first uninitialized entry
58 * @first_free: array index of first unused object reference entry
59 * @last_free: array index of last unused object reference entry
60 * @index_mask: bitmask for array index portion of reference values
61 * @start_mask: initial value for instance value portion of reference values
65 struct reference
*entries
;
75 * Object reference table consists of 2**N entries.
77 * State Object ptr Reference
78 * ----- ---------- ---------
79 * In use non-NULL XXXX|own index
80 * (XXXX changes each time entry is acquired)
81 * Free NULL YYYY|next free index
82 * (YYYY is one more than last used XXXX)
83 * Uninitialized NULL 0
85 * Entry 0 is not used; this allows index 0 to denote the end of the free list.
87 * Note that a reference value of 0 does not necessarily indicate that an
88 * entry is uninitialized, since the last entry in the free list could also
89 * have a reference value of 0 (although this is unlikely).
92 static struct ref_table tipc_ref_table
= { NULL
};
94 static DEFINE_RWLOCK(ref_table_lock
);
97 * tipc_ref_table_init - create reference table for objects
100 int tipc_ref_table_init(u32 requested_size
, u32 start
)
102 struct reference
*table
;
105 /* account for unused entry, then round up size to a power of 2 */
108 for (actual_size
= 16; actual_size
< requested_size
; actual_size
<<= 1)
111 /* allocate table & mark all entries as uninitialized */
113 table
= __vmalloc(actual_size
* sizeof(struct reference
),
114 GFP_KERNEL
| __GFP_HIGHMEM
| __GFP_ZERO
, PAGE_KERNEL
);
118 tipc_ref_table
.entries
= table
;
119 tipc_ref_table
.capacity
= requested_size
;
120 tipc_ref_table
.init_point
= 1;
121 tipc_ref_table
.first_free
= 0;
122 tipc_ref_table
.last_free
= 0;
123 tipc_ref_table
.index_mask
= actual_size
- 1;
124 tipc_ref_table
.start_mask
= start
& ~tipc_ref_table
.index_mask
;
130 * tipc_ref_table_stop - destroy reference table for objects
133 void tipc_ref_table_stop(void)
135 if (!tipc_ref_table
.entries
)
138 vfree(tipc_ref_table
.entries
);
139 tipc_ref_table
.entries
= NULL
;
143 * tipc_ref_acquire - create reference to an object
145 * Register an object pointer in reference table and lock the object.
146 * Returns a unique reference value that is used from then on to retrieve the
147 * object pointer, or to determine that the object has been deregistered.
149 * Note: The object is returned in the locked state so that the caller can
150 * register a partially initialized object, without running the risk that
151 * the object will be accessed before initialization is complete.
154 u32
tipc_ref_acquire(void *object
, spinlock_t
**lock
)
160 struct reference
*entry
= NULL
;
163 err("Attempt to acquire reference to non-existent object\n");
166 if (!tipc_ref_table
.entries
) {
167 err("Reference table not found during acquisition attempt\n");
171 /* take a free entry, if available; otherwise initialize a new entry */
173 write_lock_bh(&ref_table_lock
);
174 if (tipc_ref_table
.first_free
) {
175 index
= tipc_ref_table
.first_free
;
176 entry
= &(tipc_ref_table
.entries
[index
]);
177 index_mask
= tipc_ref_table
.index_mask
;
178 next_plus_upper
= entry
->ref
;
179 tipc_ref_table
.first_free
= next_plus_upper
& index_mask
;
180 ref
= (next_plus_upper
& ~index_mask
) + index
;
182 else if (tipc_ref_table
.init_point
< tipc_ref_table
.capacity
) {
183 index
= tipc_ref_table
.init_point
++;
184 entry
= &(tipc_ref_table
.entries
[index
]);
185 spin_lock_init(&entry
->lock
);
186 ref
= tipc_ref_table
.start_mask
+ index
;
191 write_unlock_bh(&ref_table_lock
);
194 * Grab the lock so no one else can modify this entry
195 * While we assign its ref value & object pointer
198 spin_lock_bh(&entry
->lock
);
200 entry
->object
= object
;
201 *lock
= &entry
->lock
;
203 * keep it locked, the caller is responsible
204 * for unlocking this when they're done with it
212 * tipc_ref_discard - invalidate references to an object
214 * Disallow future references to an object and free up the entry for re-use.
215 * Note: The entry's spin_lock may still be busy after discard
218 void tipc_ref_discard(u32 ref
)
220 struct reference
*entry
;
224 if (!tipc_ref_table
.entries
) {
225 err("Reference table not found during discard attempt\n");
229 index_mask
= tipc_ref_table
.index_mask
;
230 index
= ref
& index_mask
;
231 entry
= &(tipc_ref_table
.entries
[index
]);
233 write_lock_bh(&ref_table_lock
);
235 if (!entry
->object
) {
236 err("Attempt to discard reference to non-existent object\n");
239 if (entry
->ref
!= ref
) {
240 err("Attempt to discard non-existent reference\n");
245 * mark entry as unused; increment instance part of entry's reference
246 * to invalidate any subsequent references
249 entry
->object
= NULL
;
250 entry
->ref
= (ref
& ~index_mask
) + (index_mask
+ 1);
252 /* append entry to free entry list */
254 if (tipc_ref_table
.first_free
== 0)
255 tipc_ref_table
.first_free
= index
;
257 tipc_ref_table
.entries
[tipc_ref_table
.last_free
].ref
|= index
;
258 tipc_ref_table
.last_free
= index
;
261 write_unlock_bh(&ref_table_lock
);
265 * tipc_ref_lock - lock referenced object and return pointer to it
268 void *tipc_ref_lock(u32 ref
)
270 if (likely(tipc_ref_table
.entries
)) {
271 struct reference
*entry
;
273 entry
= &tipc_ref_table
.entries
[ref
&
274 tipc_ref_table
.index_mask
];
275 if (likely(entry
->ref
!= 0)) {
276 spin_lock_bh(&entry
->lock
);
277 if (likely((entry
->ref
== ref
) && (entry
->object
)))
278 return entry
->object
;
279 spin_unlock_bh(&entry
->lock
);
286 * tipc_ref_unlock - unlock referenced object
289 void tipc_ref_unlock(u32 ref
)
291 if (likely(tipc_ref_table
.entries
)) {
292 struct reference
*entry
;
294 entry
= &tipc_ref_table
.entries
[ref
&
295 tipc_ref_table
.index_mask
];
296 if (likely((entry
->ref
== ref
) && (entry
->object
)))
297 spin_unlock_bh(&entry
->lock
);
299 err("Attempt to unlock non-existent reference\n");
304 * tipc_ref_deref - return pointer referenced object (without locking it)
307 void *tipc_ref_deref(u32 ref
)
309 if (likely(tipc_ref_table
.entries
)) {
310 struct reference
*entry
;
312 entry
= &tipc_ref_table
.entries
[ref
&
313 tipc_ref_table
.index_mask
];
314 if (likely(entry
->ref
== ref
))
315 return entry
->object
;