typedef struct node {
nstring_t *key;
- uint64_t value;
+ uint64_t val;
struct node *next;
} node_t;
node_t *head;
};
-static node_t *node_alloc (const void *key_data, uint32_t key_len, uint64_t value) {
+static node_t *node_alloc (const void *key_data, uint32_t key_len, uint64_t val) {
node_t *item = (node_t *)nbd_malloc(sizeof(node_t));
memset(item, 0, sizeof(node_t));
// If <key_len> is -1 it indicates <key_data> is an integer and not a pointer
item->key = (key_len == (unsigned)-1)
? (void *)TAG_VALUE(key_data)
: ns_alloc(key_data, key_len);
- item->value = value;
+ item->val = val;
return item;
}
+static void node_free (node_t *item) {
+ if (!IS_TAGGED(item->key)) {
+ nbd_free(item->key);
+ }
+ nbd_free(item);
+}
+
+static void node_defer_free (node_t *item) {
+ if (!IS_TAGGED(item->key)) {
+ nbd_defer_free(item->key);
+ }
+ nbd_defer_free(item);
+}
+
list_t *ll_alloc (void) {
list_t *ll = (list_t *)nbd_malloc(sizeof(list_t));
ll->head = node_alloc(" ", 0, 0);
while (item != NULL) {
node_t *next = item->next;
TRACE("l3", "find_pred: visiting item %p (next %p)", item, next);
- TRACE("l3", "find_pred: key %p", STRIP_TAG(item->key), item->value);
+ TRACE("l3", "find_pred: key %p", STRIP_TAG(item->key), item->val);
// A tag means an item is logically removed but not physically unlinked yet.
while (EXPECT_FALSE(IS_TAGGED(next))) {
TRACE("l3", "find_pred: now item is %p next is %p", item, next);
// The thread that completes the unlink should free the memory.
- nbd_defer_free(other);
+ node_defer_free(other);
} else {
TRACE("l3", "find_pred: lost race to unlink from pred %p; its link changed to %p", pred, other);
if (IS_TAGGED(other))
// Fast find. Do not help unlink partially removed nodes and do not return the found item's predecessor.
uint64_t ll_lookup (list_t *ll, const void *key_data, uint32_t key_len) {
- TRACE("l3", "ll_lookup: searching for key %p in ll %p", key_data, ll);
+ TRACE("l3", "ll_lookup: searching for key %p in list %p", key_data, ll);
node_t *item = find_pred(NULL, ll, key_data, key_len, FALSE);
// If we found an <item> matching the key return its value.
- return item != NULL ? item->value : DOES_NOT_EXIST;
+ return item != NULL ? item->val : DOES_NOT_EXIST;
}
// Insert a new item if a matching key doesn't already exist in <ll>
-uint64_t ll_add (list_t *ll, const void *key_data, uint32_t key_len, uint64_t value) {
- TRACE("l3", "ll_add: inserting key %p value %p", key_data, value);
- node_t *pred;
- node_t *item = NULL;
+uint64_t ll_cas (list_t *ll, const void *key_data, uint32_t key_len, uint64_t expected_val, uint64_t new_val) {
+ assert(new_val != DOES_NOT_EXIST);
+ TRACE("l3", "ll_cas: inserting key %p val %p", key_data, new_val);
do {
- node_t *next = find_pred(&pred, ll, key_data, key_len, TRUE);
+ node_t *pred;
+ node_t *old_item = find_pred(&pred, ll, key_data, key_len, TRUE);
// If a node matching the key already exists in <ll> return its value.
- if (next != NULL) {
- TRACE("l3", "ll_add: there is already an item %p (value %p) with the same key", next, next->value);
- if (EXPECT_FALSE(item != NULL)) { nbd_free(item); }
- return next->value;
+ if (old_item != NULL) {
+ TRACE("l3", "ll_cas: there is already an item %p (value %p) with the same key", old_item, old_item->val);
+ return old_item->val;
}
- next = pred->next;
- TRACE("l3", "ll_add: attempting to insert item between %p and %p", pred, next);
- if (EXPECT_TRUE(item == NULL)) { item = node_alloc(key_data, key_len, value); }
- item->next = next;
- node_t *other = SYNC_CAS(&pred->next, next, item);
+ TRACE("l3", "ll_cas: attempting to insert item between %p and %p", pred, pred->next);
+ node_t *new_item = node_alloc(key_data, key_len, new_val);
+ node_t *next = new_item->next = pred->next;
+ node_t *other = SYNC_CAS(&pred->next, next, new_item);
if (other == next) {
- TRACE("l3", "ll_add: successfully inserted item %p", item, 0);
+ TRACE("l3", "ll_cas: successfully inserted item %p", new_item, 0);
return DOES_NOT_EXIST; // success
}
- TRACE("l3", "ll_add: failed to change pred's link: expected %p found %p", next, other);
+ TRACE("l3", "ll_cas: failed to change pred's link: expected %p found %p", next, other);
+ node_free(new_item);
} while (1);
}
uint64_t ll_remove (list_t *ll, const void *key_data, uint32_t key_len) {
- TRACE("l3", "ll_remove: removing item with key %p from ll %p", key_data, ll);
+ TRACE("l3", "ll_remove: removing item with key %p from list %p", key_data, ll);
node_t *pred;
node_t *item = find_pred(&pred, ll, key_data, key_len, TRUE);
if (item == NULL) {
- TRACE("l3", "ll_remove: remove failed, an item with a matching key does not exist in the ll", 0, 0);
+ TRACE("l3", "ll_remove: remove failed, an item with a matching key does not exist in the list", 0, 0);
return DOES_NOT_EXIST;
}
return DOES_NOT_EXIST;
}
- uint64_t value = item->value;
+ uint64_t val = item->val;
- // Unlink <item> from <ll>.
+ // Unlink <item> from <ll>. If we lose a race to another thread just back off. It is safe to leave the
+ // item logically removed for a later call (or some other thread) to physically unlink. By marking the
+ // item earlier, we logically removed it.
TRACE("l3", "ll_remove: link item's pred %p to it's successor %p", pred, next);
node_t *other;
if ((other = SYNC_CAS(&pred->next, item, next)) != item) {
TRACE("l3", "ll_remove: unlink failed; pred's link changed from %p to %p", item, other);
- // By marking the item earlier, we logically removed it. It is safe to leave the item.
- // Another thread will finish physically removing it from the ll.
- return value;
+ return val;
}
// The thread that completes the unlink should free the memory.
- nbd_defer_free(item);
- return value;
+ node_defer_free(item);
+ return val;
}
void ll_print (list_t *ll) {
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