/*
* net/tipc/ref.c: TIPC object registry code
- *
+ *
* Copyright (c) 1991-2006, Ericsson AB
- * Copyright (c) 2004-2005, Wind River Systems
+ * Copyright (c) 2004-2007, Wind River Systems
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
#include "core.h"
#include "ref.h"
-#include "port.h"
-#include "subscr.h"
-#include "name_distr.h"
-#include "name_table.h"
-#include "config.h"
-#include "discover.h"
-#include "bearer.h"
-#include "node.h"
-#include "bcast.h"
+
+/**
+ * struct reference - TIPC object reference entry
+ * @object: pointer to object associated with reference entry
+ * @lock: spinlock controlling access to object
+ * @ref: reference value for object (combines instance & array index info)
+ */
+
+struct reference {
+ void *object;
+ spinlock_t lock;
+ u32 ref;
+};
+
+/**
+ * struct tipc_ref_table - table of TIPC object reference entries
+ * @entries: pointer to array of reference entries
+ * @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 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).
*/
-struct ref_table tipc_ref_table = { 0 };
+static struct ref_table tipc_ref_table = { NULL };
-static rwlock_t ref_table_lock = RW_LOCK_UNLOCKED;
+static DEFINE_RWLOCK(ref_table_lock);
/**
* tipc_ref_table_init - create reference table for objects
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 = (struct reference *)vmalloc(sz * sizeof(struct reference));
+ /* 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 = 0;
- table[i].lock = SPIN_LOCK_UNLOCKED;
- 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;
}
return;
vfree(tipc_ref_table.entries);
- tipc_ref_table.entries = 0;
+ tipc_ref_table.entries = NULL;
}
/**
* tipc_ref_acquire - create reference to an object
- *
- * Return a unique reference value which can be translated back to the pointer
- * 'object' at a later time. Also, pass back a pointer to the lock protecting
- * the object, but without locking it.
+ *
+ * Register an object pointer in reference table and lock the object.
+ * Returns a unique reference value that is used from then on to retrieve the
+ * object pointer, or to determine that the object has been deregistered.
+ *
+ * Note: The object is returned in the locked state so that the caller can
+ * register a partially initialized object, without running the risk that
+ * the object will be accessed before initialization is complete.
*/
u32 tipc_ref_acquire(void *object, spinlock_t **lock)
u32 index;
u32 index_mask;
u32 next_plus_upper;
- u32 reference = 0;
+ u32 ref;
- assert(tipc_ref_table.entries && object);
+ if (!object) {
+ err("Attempt to acquire reference to non-existent object\n");
+ return 0;
+ }
+ if (!tipc_ref_table.entries) {
+ err("Reference table not found during acquisition attempt\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;
entry = &(tipc_ref_table.entries[index]);
index_mask = tipc_ref_table.index_mask;
- /* take lock in case a previous user of entry still holds it */
- spin_lock_bh(&entry->lock);
- next_plus_upper = entry->data.next_plus_upper;
+ /* take lock in case a previous user of entry still holds it */
+ spin_lock_bh(&entry->lock);
+ next_plus_upper = entry->ref;
tipc_ref_table.first_free = next_plus_upper & index_mask;
- reference = (next_plus_upper & ~index_mask) + index;
- entry->data.reference = reference;
+ ref = (next_plus_upper & ~index_mask) + index;
+ entry->ref = ref;
+ entry->object = object;
+ *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);
+ spin_lock_bh(&entry->lock);
+ ref = tipc_ref_table.start_mask + index;
+ entry->ref = ref;
entry->object = object;
- if (lock != 0)
- *lock = &entry->lock;
- spin_unlock_bh(&entry->lock);
+ *lock = &entry->lock;
+ }
+ else {
+ ref = 0;
}
write_unlock_bh(&ref_table_lock);
- return reference;
+
+ return ref;
}
/**
* tipc_ref_discard - invalidate references to an object
- *
+ *
* Disallow future references to an object and free up the entry for re-use.
* Note: The entry's spin_lock may still be busy after discard
*/
void tipc_ref_discard(u32 ref)
{
struct reference *entry;
- u32 index;
+ u32 index;
u32 index_mask;
- assert(tipc_ref_table.entries);
- assert(ref != 0);
+ 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]);
- assert(entry->object != 0);
- assert(entry->data.reference == ref);
- /* mark entry as unused */
- entry->object = 0;
+ write_lock_bh(&ref_table_lock);
+
+ if (!entry->object) {
+ err("Attempt to discard reference to non-existent object\n");
+ goto exit;
+ }
+ if (entry->ref != ref) {
+ err("Attempt to discard non-existent reference\n");
+ goto exit;
+ }
+
+ /*
+ * mark entry as unused; increment instance part of entry's reference
+ * to invalidate any subsequent references
+ */
+
+ entry->object = NULL;
+ entry->ref = (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.entries[tipc_ref_table.last_free].ref |= 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);
}
+/**
+ * tipc_ref_lock - lock referenced object and return pointer to it
+ */
+
+void *tipc_ref_lock(u32 ref)
+{
+ if (likely(tipc_ref_table.entries)) {
+ struct reference *entry;
+
+ entry = &tipc_ref_table.entries[ref &
+ tipc_ref_table.index_mask];
+ if (likely(entry->ref != 0)) {
+ spin_lock_bh(&entry->lock);
+ if (likely((entry->ref == ref) && (entry->object)))
+ return entry->object;
+ spin_unlock_bh(&entry->lock);
+ }
+ }
+ return NULL;
+}
+
+/**
+ * tipc_ref_unlock - unlock referenced object
+ */
+
+void tipc_ref_unlock(u32 ref)
+{
+ if (likely(tipc_ref_table.entries)) {
+ struct reference *entry;
+
+ entry = &tipc_ref_table.entries[ref &
+ tipc_ref_table.index_mask];
+ if (likely((entry->ref == ref) && (entry->object)))
+ spin_unlock_bh(&entry->lock);
+ else
+ err("Attempt to unlock non-existent reference\n");
+ }
+}
+
+/**
+ * tipc_ref_deref - return pointer referenced object (without locking it)
+ */
+
+void *tipc_ref_deref(u32 ref)
+{
+ if (likely(tipc_ref_table.entries)) {
+ struct reference *entry;
+
+ entry = &tipc_ref_table.entries[ref &
+ tipc_ref_table.index_mask];
+ if (likely(entry->ref == ref))
+ return entry->object;
+ }
+ return NULL;
+}
+
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