// Setting MAX_LEVEL to 0 essentially makes this data structure the Harris-Michael lock-free list (in list.c).
#define MAX_LEVEL 31
-typedef struct node {
- void *key;
- uint64_t val;
+typedef struct sl_iter node_t;
+
+struct sl_iter {
+ map_key_t key;
+ map_val_t val;
int top_level;
- struct node *next[];
-} node_t;
+ node_t *next[];
+};
struct sl {
node_t *head;
return n;
}
-static node_t *node_alloc (int level, void *key, uint64_t val) {
+static node_t *node_alloc (int level, map_key_t key, map_val_t val) {
assert(level >= 0 && level <= MAX_LEVEL);
size_t sz = sizeof(node_t) + (level + 1) * sizeof(node_t *);
node_t *item = (node_t *)nbd_malloc(sz);
void sl_free (skiplist_t *sl) {
node_t *item = sl->head->next[0];
while (item) {
- node_t *next = (node_t *)STRIP_TAG(item->next[0]);
+ node_t *next = (node_t *)STRIP_TAG(item->next[0], TAG1);
nbd_free(item);
item = next;
}
uint64_t count = 0;
node_t *item = sl->head->next[0];
while (item) {
- if (!IS_TAGGED(item->next[0])) {
+ if (!IS_TAGGED(item->next[0], TAG1)) {
count++;
}
- item = (node_t *)STRIP_TAG(item->next[0]);
+ item = (node_t *)STRIP_TAG(item->next[0], TAG1);
}
return count;
}
-static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl, void *key, int help_remove) {
+static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl, map_key_t key, int help_remove) {
node_t *pred = sl->head;
node_t *item = NULL;
TRACE("s2", "find_preds: searching for key %p in skiplist (head is %p)", key, pred);
for (int level = start_level; level >= 0; --level) {
TRACE("s3", "find_preds: level %llu", level, 0);
item = pred->next[level];
- if (EXPECT_FALSE(IS_TAGGED(item))) {
+ if (EXPECT_FALSE(IS_TAGGED(item, TAG1))) {
TRACE("s2", "find_preds: pred %p is marked for removal (item %p); retry", pred, item);
return find_preds(preds, succs, n, sl, key, help_remove); // retry
}
node_t *next = item->next[level];
// A tag means an item is logically removed but not physically unlinked yet.
- while (EXPECT_FALSE(IS_TAGGED(next))) {
+ while (EXPECT_FALSE(IS_TAGGED(next, TAG1))) {
// Skip over logically removed items.
if (!help_remove) {
- item = (node_t *)STRIP_TAG(item->next);
+ item = (node_t *)STRIP_TAG(item->next, TAG1);
if (EXPECT_FALSE(item == NULL))
break;
TRACE("s3", "find_preds: skipping marked item %p (next is %p)", item, next);
// Unlink logically removed items.
node_t *other;
TRACE("s3", "find_preds: unlinking marked item %p; next is %p", item, next);
- if ((other = SYNC_CAS(&pred->next[level], item, STRIP_TAG(next))) == item) {
- item = (node_t *)STRIP_TAG(next);
+ if ((other = SYNC_CAS(&pred->next[level], item, STRIP_TAG(next, TAG1))) == item) {
+ item = (node_t *)STRIP_TAG(next, TAG1);
if (EXPECT_FALSE(item == NULL))
break;
next = item->next[level];
} else {
TRACE("s3", "find_preds: lost race to unlink item %p from pred %p", item, pred);
TRACE("s3", "find_preds: pred's link changed to %p", other, 0);
- if (IS_TAGGED(other))
+ if (IS_TAGGED(other, TAG1))
return find_preds(preds, succs, n, sl, key, help_remove); // retry
item = other;
if (EXPECT_FALSE(item == NULL))
break;
TRACE("s4", "find_preds: visiting item %p (next is %p)", item, next);
- TRACE("s4", "find_preds: key %p val %p", STRIP_TAG(item->key), item->val);
+ TRACE("s4", "find_preds: key %p val %p", STRIP_TAG(item->key, TAG1), item->val);
if (EXPECT_TRUE(sl->key_type == NULL)) {
d = (uint64_t)item->key - (uint64_t)key;
}
// Fast find that does not help unlink partially removed nodes and does not return the node's predecessors.
-uint64_t sl_lookup (skiplist_t *sl, void *key) {
+map_val_t sl_lookup (skiplist_t *sl, map_key_t key) {
TRACE("s1", "sl_lookup: searching for key %p in skiplist %p", key, sl);
node_t *item = find_preds(NULL, NULL, 0, sl, key, FALSE);
// If we found an <item> matching the <key> return its value.
if (item != NULL) {
- uint64_t val = item->val;
+ map_val_t val = item->val;
if (val != DOES_NOT_EXIST) {
TRACE("s1", "sl_lookup: found item %p. val %p. returning item", item, item->val);
return val;
return DOES_NOT_EXIST;
}
-uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expectation, uint64_t new_val) {
+map_key_t sl_min_key (skiplist_t *sl) {
+ node_t *item = sl->head->next[0];
+ while (item != NULL) {
+ node_t *next = item->next[0];
+ if (!IS_TAGGED(next, TAG1))
+ return item->key;
+ item = (node_t *)STRIP_TAG(next, TAG1);
+ }
+ return DOES_NOT_EXIST;
+}
+
+map_val_t sl_cas (skiplist_t *sl, map_key_t key, map_val_t expectation, map_val_t new_val) {
TRACE("s1", "sl_cas: key %p skiplist %p", key, sl);
TRACE("s1", "sl_cas: expectation %p new value %p", expectation, new_val);
ASSERT((int64_t)new_val > 0);
// First insert <new_item> into the bottom level.
TRACE("s3", "sl_cas: attempting to insert item between %p and %p", preds[0], nexts[0]);
- void *new_key = (sl->key_type == NULL) ? key : sl->key_type->clone(key);
+ map_key_t new_key = (sl->key_type == NULL) ? key : sl->key_type->clone(key);
new_item = node_alloc(n, new_key, new_val);
node_t *pred = preds[0];
node_t *next = new_item->next[0] = nexts[0];
}
// Found an item in the skiplist that matches the key.
- uint64_t old_item_val = old_item->val;
+ map_val_t old_item_val = old_item->val;
do {
// If the item's value is DOES_NOT_EXIST it means another thread removed the node out from under us.
if (EXPECT_FALSE(old_item_val == DOES_NOT_EXIST)) {
// replace DOES_NOT_EXIST with our value. Then another thread that is updating the value could think it
// succeeded and return our value even though we indicated that the node has been removed. If the CAS
// fails it means another thread either removed the node or updated its value.
- uint64_t ret_val = SYNC_CAS(&old_item->val, old_item_val, new_val);
+ map_val_t ret_val = SYNC_CAS(&old_item->val, old_item_val, new_val);
if (ret_val == old_item_val) {
TRACE("s1", "sl_cas: the CAS succeeded. updated the value of the item", 0, 0);
return ret_val; // success
do {
// There in no need to continue linking in the item if another thread removed it.
node_t *old_next = ((volatile node_t *)new_item)->next[level];
- if (IS_TAGGED(old_next))
+ if (IS_TAGGED(old_next, TAG1))
return DOES_NOT_EXIST; // success
// Use a CAS so we do not inadvertantly stomp on a mark another thread placed on the item.
return DOES_NOT_EXIST; // success
}
-uint64_t sl_remove (skiplist_t *sl, void *key) {
+map_val_t sl_remove (skiplist_t *sl, map_key_t key) {
TRACE("s1", "sl_remove: removing item with key %p from skiplist %p", key, sl);
node_t *preds[MAX_LEVEL+1];
node_t *item = find_preds(preds, NULL, -1, sl, key, TRUE);
node_t *old_next = item->next[level];
do {
next = old_next;
- old_next = SYNC_CAS(&item->next[level], next, TAG_VALUE(next));
- if (IS_TAGGED(old_next)) {
+ old_next = SYNC_CAS(&item->next[level], next, TAG_VALUE(next, TAG1));
+ if (IS_TAGGED(old_next, TAG1)) {
TRACE("s2", "sl_remove: %p is already marked for removal by another thread at level %llu", item, level);
break;
}
} while (next != old_next);
node_t *pred = preds[level];
- TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_TAG(next));
+ TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_TAG(next, TAG1));
node_t *other = NULL;
- if ((other = SYNC_CAS(&pred->next[level], item, STRIP_TAG(next))) != item) {
+ if ((other = SYNC_CAS(&pred->next[level], item, STRIP_TAG(next, TAG1))) != item) {
TRACE("s1", "sl_remove: unlink failed; pred's link changed from %p to %p", item, other);
// If our former predecessor now points past us we know another thread unlinked us. Otherwise, we need
// to search for a new set of preds.
continue; // <pred> points past <item> to the end of the list; go on to the next level.
int d = -1;
- if (!IS_TAGGED(other)) {
+ if (!IS_TAGGED(other, TAG1)) {
if (EXPECT_TRUE(sl->key_type == NULL)) {
d = (uint64_t)item->key - (uint64_t)other->key;
} else {
node_t *old_next = item->next[0];
do {
next = old_next;
- old_next = SYNC_CAS(&item->next[0], next, TAG_VALUE(next));
- if (IS_TAGGED(old_next)) {
+ old_next = SYNC_CAS(&item->next[0], next, TAG_VALUE(next, TAG1));
+ if (IS_TAGGED(old_next, TAG1)) {
TRACE("s2", "sl_remove: %p is already marked for removal by another thread at level 0", item, 0);
return DOES_NOT_EXIST;
}
// Atomically swap out the item's value in case another thread is updating the item while we are
// removing it. This establishes which operation occurs first logically, the update or the remove.
- uint64_t val = SYNC_SWAP(&item->val, DOES_NOT_EXIST);
+ map_val_t val = SYNC_SWAP(&item->val, DOES_NOT_EXIST);
TRACE("s2", "sl_remove: replaced item %p's value with DOES_NOT_EXIT", item, 0);
node_t *pred = preds[0];
- TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_TAG(next));
- if (SYNC_CAS(&pred->next[0], item, STRIP_TAG(next))) {
+ TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_TAG(next, TAG1));
+ if (SYNC_CAS(&pred->next[0], item, STRIP_TAG(next, TAG1))) {
TRACE("s2", "sl_remove: unlinked item %p from the skiplist at level 0", item, 0);
// The thread that completes the unlink should free the memory.
if (sl->key_type != NULL) {
int i = 0;
while (item) {
node_t *next = item->next[level];
- printf("%s%p ", IS_TAGGED(next) ? "*" : "", item);
- item = (node_t *)STRIP_TAG(next);
+ printf("%s%p ", IS_TAGGED(next, TAG1) ? "*" : "", item);
+ item = (node_t *)STRIP_TAG(next, TAG1);
if (i++ > 30) {
printf("...");
break;
node_t *item = sl->head;
int i = 0;
while (item) {
- int is_marked = IS_TAGGED(item->next[0]);
+ int is_marked = IS_TAGGED(item->next[0], TAG1);
printf("%s%p:%p ", is_marked ? "*" : "", item, item->key);
if (item != sl->head) {
printf("[%d]", item->top_level);
printf("[HEAD]");
}
for (int level = 1; level <= item->top_level; ++level) {
- node_t *next = (node_t *)STRIP_TAG(item->next[level]);
- is_marked = IS_TAGGED(item->next[0]);
+ node_t *next = (node_t *)STRIP_TAG(item->next[level], TAG1);
+ is_marked = IS_TAGGED(item->next[0], TAG1);
printf(" %p%s", next, is_marked ? "*" : "");
if (item == sl->head && item->next[level] == NULL)
break;
}
printf("\n");
fflush(stdout);
- item = (node_t *)STRIP_TAG(item->next[0]);
+ item = (node_t *)STRIP_TAG(item->next[0], TAG1);
if (i++ > 30) {
printf("...\n");
break;
}
}
}
+
+sl_iter_t *sl_iter_begin (skiplist_t *sl, map_key_t key) {
+ node_t *iter = node_alloc(0, 0, 0);
+ find_preds(NULL, &iter->next[0], 0, sl, key, FALSE);
+ return iter;
+}
+
+map_val_t sl_iter_next (sl_iter_t *iter, map_key_t *key_ptr) {
+ assert(iter);
+ node_t *item = iter->next[0];
+ while (item != NULL && IS_TAGGED(item->next[0], TAG1)) {
+ item = (node_t *)STRIP_TAG(item->next[0], TAG1);
+ }
+ if (item == NULL) {
+ iter->next[0] = NULL;
+ return DOES_NOT_EXIST;
+ }
+ iter->next[0] = item->next[0];
+ if (key_ptr != NULL) {
+ *key_ptr = item->key;
+ }
+ return item->val;
+}
+
+void sl_iter_free (sl_iter_t *iter) {
+ nbd_free(iter);
+}