* struct reference - TIPC object reference entry
* @object: pointer to object associated with reference entry
* @lock: spinlock controlling access to object
- * @data: reference value associated with object (or link to next unused entry)
+ * @data: reference value for object (combines instance & array index info)
*/
struct reference {
/**
* struct tipc_ref_table - table of TIPC object reference entries
* @entries: pointer to array of reference entries
- * @index_mask: bitmask for array index portion of reference values
+ * @capacity: array index of first unusable entry
+ * @init_point: array index of first uninitialized entry
* @first_free: array index of first unused object reference entry
* @last_free: array index of last unused object reference entry
+ * @index_mask: bitmask for array index portion of reference values
+ * @start_mask: initial value for instance value portion of reference values
*/
struct ref_table {
struct reference *entries;
- u32 index_mask;
+ u32 capacity;
+ u32 init_point;
u32 first_free;
u32 last_free;
+ u32 index_mask;
+ u32 start_mask;
};
/*
* Object reference table consists of 2**N entries.
*
- * A used entry has object ptr != 0, reference == XXXX|own index
- * (XXXX changes each time entry is acquired)
- * A free entry has object ptr == 0, reference == YYYY|next free index
- * (YYYY is one more than last used XXXX)
+ * State Object ptr Reference
+ * ----- ---------- ---------
+ * In use non-NULL XXXX|own index
+ * (XXXX changes each time entry is acquired)
+ * Free NULL YYYY|next free index
+ * (YYYY is one more than last used XXXX)
+ * Uninitialized NULL 0
*
- * Free list is initially chained from entry (2**N)-1 to entry 1.
- * Entry 0 is not used to allow index 0 to indicate the end of the free list.
+ * Entry 0 is not used; this allows index 0 to denote the end of the free list.
*
- * Note: Any accidental reference of the form XXXX|0--0 won't match entry 0
- * because entry 0's reference field has the form XXXX|1--1.
+ * Note that a reference value of 0 does not necessarily indicate that an
+ * entry is uninitialized, since the last entry in the free list could also
+ * have a reference value of 0 (although this is unlikely).
*/
static struct ref_table tipc_ref_table = { NULL };
int tipc_ref_table_init(u32 requested_size, u32 start)
{
struct reference *table;
- u32 sz = 1 << 4;
- u32 index_mask;
- int i;
+ u32 actual_size;
- while (sz < requested_size) {
- sz <<= 1;
- }
- table = vmalloc(sz * sizeof(*table));
+ /* account for unused entry, then round up size to a power of 2 */
+
+ requested_size++;
+ for (actual_size = 16; actual_size < requested_size; actual_size <<= 1)
+ /* do nothing */ ;
+
+ /* allocate table & mark all entries as uninitialized */
+
+ table = __vmalloc(actual_size * sizeof(struct reference),
+ GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, PAGE_KERNEL);
if (table == NULL)
return -ENOMEM;
- write_lock_bh(&ref_table_lock);
- index_mask = sz - 1;
- for (i = sz - 1; i >= 0; i--) {
- table[i].object = NULL;
- spin_lock_init(&table[i].lock);
- table[i].data.next_plus_upper = (start & ~index_mask) + i - 1;
- }
tipc_ref_table.entries = table;
- tipc_ref_table.index_mask = index_mask;
- tipc_ref_table.first_free = sz - 1;
- tipc_ref_table.last_free = 1;
- write_unlock_bh(&ref_table_lock);
+ tipc_ref_table.capacity = requested_size;
+ tipc_ref_table.init_point = 1;
+ tipc_ref_table.first_free = 0;
+ tipc_ref_table.last_free = 0;
+ tipc_ref_table.index_mask = actual_size - 1;
+ tipc_ref_table.start_mask = start & ~tipc_ref_table.index_mask;
+
return TIPC_OK;
}
u32 index;
u32 index_mask;
u32 next_plus_upper;
- u32 reference = 0;
+ u32 reference;
if (!object) {
err("Attempt to acquire reference to non-existent object\n");
return 0;
}
+ /* take a free entry, if available; otherwise initialize a new entry */
+
write_lock_bh(&ref_table_lock);
if (tipc_ref_table.first_free) {
index = tipc_ref_table.first_free;
reference = (next_plus_upper & ~index_mask) + index;
entry->data.reference = reference;
entry->object = object;
- if (lock != NULL)
- *lock = &entry->lock;
spin_unlock_bh(&entry->lock);
+ *lock = &entry->lock;
+ }
+ else if (tipc_ref_table.init_point < tipc_ref_table.capacity) {
+ index = tipc_ref_table.init_point++;
+ entry = &(tipc_ref_table.entries[index]);
+ spin_lock_init(&entry->lock);
+ reference = tipc_ref_table.start_mask + index;
+ entry->data.reference = reference;
+ entry->object = object;
+ *lock = &entry->lock;
+ }
+ else {
+ reference = 0;
}
write_unlock_bh(&ref_table_lock);
+
return reference;
}
u32 index;
u32 index_mask;
- if (!ref) {
- err("Attempt to discard reference 0\n");
- return;
- }
if (!tipc_ref_table.entries) {
err("Reference table not found during discard attempt\n");
return;
}
- write_lock_bh(&ref_table_lock);
index_mask = tipc_ref_table.index_mask;
index = ref & index_mask;
entry = &(tipc_ref_table.entries[index]);
+ write_lock_bh(&ref_table_lock);
+
if (!entry->object) {
err("Attempt to discard reference to non-existent object\n");
goto exit;
goto exit;
}
- /* mark entry as unused */
+ /*
+ * mark entry as unused; increment upper bits of entry's data field
+ * to invalidate any subsequent references
+ */
+
entry->object = NULL;
+ entry->data.next_plus_upper = (ref & ~index_mask) + (index_mask + 1);
+
+ /* append entry to free entry list */
+
if (tipc_ref_table.first_free == 0)
tipc_ref_table.first_free = index;
else
- /* next_plus_upper is always XXXX|0--0 for last free entry */
tipc_ref_table.entries[tipc_ref_table.last_free].
data.next_plus_upper |= index;
tipc_ref_table.last_free = index;
- /* increment upper bits of entry to invalidate subsequent references */
- entry->data.next_plus_upper = (ref & ~index_mask) + (index_mask + 1);
exit:
write_unlock_bh(&ref_table_lock);
}
struct reference *r;
r = &tipc_ref_table.entries[ref & tipc_ref_table.index_mask];
- spin_lock_bh(&r->lock);
- if (likely(r->data.reference == ref))
- return r->object;
- spin_unlock_bh(&r->lock);
+
+ if (likely(r->data.reference != 0)) {
+ spin_lock_bh(&r->lock);
+ if (likely((r->data.reference == ref) && (r->object)))
+ return r->object;
+ spin_unlock_bh(&r->lock);
+ }
}
return NULL;
}
struct reference *r;
r = &tipc_ref_table.entries[ref & tipc_ref_table.index_mask];
- if (likely(r->data.reference == ref))
+
+ if (likely((r->data.reference == ref) && (r->object)))
spin_unlock_bh(&r->lock);
else
err("tipc_ref_unlock() invoked using "
- "obsolete reference\n");
+ "invalid reference\n");
}
}
projects / linux-2.6 / commitdiff