#define MAX_LEVEL 31
typedef struct node {
- void *key;
- uint64_t val;
+ map_key_t key;
+ map_val_t val;
int top_level;
- struct node *next[];
+ markable_t next[];
} node_t;
+struct sl_iter {
+ node_t *next;
+};
+
struct sl {
node_t *head;
const datatype_t *key_type;
};
+// Marking the <next> field of a node logically removes it from the list
+#if 0
+static inline markable_t MARK_NODE(node_t * x) { return TAG_VALUE((markable_t)x, TAG1); }
+static inline int HAS_MARK(markable_t x) { return (IS_TAGGED(x, TAG1) == TAG1); }
+static inline node_t * GET_NODE(markable_t x) { assert(!HAS_MARK(x)); return (node_t *)x; }
+static inline node_t * STRIP_MARK(markable_t x) { return ((node_t *)STRIP_TAG(x, TAG1)); }
+#else
+#define MARK_NODE(x) TAG_VALUE((markable_t)(x), TAG1)
+#define HAS_MARK(x) (IS_TAGGED((x), TAG1) == TAG1)
+#define GET_NODE(x) ((node_t *)(x))
+#define STRIP_MARK(x) ((node_t *)STRIP_TAG((x), TAG1))
+#endif
+
static int random_level (void) {
unsigned r = nbd_rand();
if (r & 1)
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);
skiplist_t *sl_alloc (const datatype_t *key_type) {
skiplist_t *sl = (skiplist_t *)nbd_malloc(sizeof(skiplist_t));
sl->key_type = key_type;
- sl->head = node_alloc(MAX_LEVEL, NULL, 0);
+ sl->head = node_alloc(MAX_LEVEL, 0, 0);
memset(sl->head->next, 0, (MAX_LEVEL+1) * sizeof(skiplist_t *));
return sl;
}
void sl_free (skiplist_t *sl) {
- node_t *item = sl->head->next[0];
+ node_t *item = GET_NODE(sl->head->next[0]);
while (item) {
- node_t *next = (node_t *)STRIP_TAG(item->next[0], TAG1);
+ node_t *next = STRIP_MARK(item->next[0]);
+ if (sl->key_type != NULL) {
+ nbd_free((void *)item->key);
+ }
nbd_free(item);
item = next;
}
}
-uint64_t sl_count (skiplist_t *sl) {
- uint64_t count = 0;
- node_t *item = sl->head->next[0];
+size_t sl_count (skiplist_t *sl) {
+ size_t count = 0;
+ node_t *item = GET_NODE(sl->head->next[0]);
while (item) {
- if (!IS_TAGGED(item->next[0], TAG1)) {
+ if (!HAS_MARK(item->next[0])) {
count++;
}
- item = (node_t *)STRIP_TAG(item->next[0], TAG1);
+ item = STRIP_MARK(item->next[0]);
}
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);
#if MAX_LEVEL > 2
// Optimization for small lists. No need to traverse empty higher levels.
start_level = 2;
- while (pred->next[start_level+1] != NULL) {
+ while (pred->next[start_level+1] != DOES_NOT_EXIST) {
start_level += start_level - 1;
if (EXPECT_FALSE(start_level >= MAX_LEVEL)) {
start_level = MAX_LEVEL;
// Traverse the levels of <sl> from the top level to the bottom
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, TAG1))) {
- TRACE("s2", "find_preds: pred %p is marked for removal (item %p); retry", pred, item);
+ markable_t next = pred->next[level];
+ if (EXPECT_FALSE(HAS_MARK(next))) {
+ TRACE("s2", "find_preds: pred %p is marked for removal (next %p); retry", pred, next);
return find_preds(preds, succs, n, sl, key, help_remove); // retry
}
+ item = GET_NODE(next);
while (item != NULL) {
- node_t *next = item->next[level];
+ next = item->next[level];
// A tag means an item is logically removed but not physically unlinked yet.
- while (EXPECT_FALSE(IS_TAGGED(next, TAG1))) {
+ while (EXPECT_FALSE(HAS_MARK(next))) {
// Skip over logically removed items.
if (!help_remove) {
- item = (node_t *)STRIP_TAG(item->next, TAG1);
+ item = STRIP_MARK(next);
if (EXPECT_FALSE(item == NULL))
break;
- TRACE("s3", "find_preds: skipping marked item %p (next is %p)", item, next);
next = item->next[level];
+ TRACE("s3", "find_preds: skipping marked item %p (next is 0x%llx)", item, next);
continue;
}
// 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, TAG1))) == item) {
- item = (node_t *)STRIP_TAG(next, TAG1);
- if (EXPECT_FALSE(item == NULL))
- break;
- next = item->next[level];
- TRACE("s3", "find_preds: now the current item is %p next is %p", item, next);
+ TRACE("s3", "find_preds: unlinking marked item %p; next is 0x%llx", item, next);
+ markable_t other = SYNC_CAS(&pred->next[level], item, STRIP_MARK(next));
+ if (other == (markable_t)item) {
+ item = STRIP_MARK(next);
+ next = (item != NULL) ? item->next[level] : DOES_NOT_EXIST;
+ TRACE("s3", "find_preds: now the current item is %p next is 0x%llx", item, next);
// The thread that completes the unlink should free the memory.
if (level == 0) {
+ node_t *unlinked = GET_NODE(other);
if (sl->key_type != NULL) {
- nbd_defer_free((void*)other->key);
+ nbd_defer_free((void *)unlinked->key);
}
- nbd_defer_free(other);
+ nbd_defer_free(unlinked);
}
} 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, TAG1))
+ if (HAS_MARK(other))
return find_preds(preds, succs, n, sl, key, help_remove); // retry
- item = other;
- if (EXPECT_FALSE(item == NULL))
- break;
- next = item->next[level];
+ item = GET_NODE(other);
+ next = (item != NULL) ? item->next[level] : DOES_NOT_EXIST;
}
}
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, TAG1), item->val);
+ TRACE("s4", "find_preds: key %p val %p", STRIP_MARK(item->key), item->val);
if (EXPECT_TRUE(sl->key_type == NULL)) {
- d = (uint64_t)item->key - (uint64_t)key;
+ d = item->key - key;
} else {
- d = sl->key_type->cmp(item->key, key);
+ d = sl->key_type->cmp((void *)item->key, (void *)key);
}
if (d >= 0) {
}
pred = item;
- item = next;
+ item = GET_NODE(next);
}
// The cast to unsigned is for the case when n is -1.
// fill in empty levels
if (n == -1 && item != NULL) {
+ assert(item->top_level <= MAX_LEVEL);
for (int level = start_level + 1; level <= item->top_level; ++level) {
preds[level] = sl->head;
}
}
// 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;
}
-void *sl_min_key (skiplist_t *sl) {
- node_t *item = sl->head->next[0];
+map_key_t sl_min_key (skiplist_t *sl) {
+ node_t *item = GET_NODE(sl->head->next[0]);
while (item != NULL) {
- node_t *next = item->next[0];
- if (!IS_TAGGED(next, TAG1))
+ markable_t next = item->next[0];
+ if (!HAS_MARK(next))
return item->key;
- item = (node_t *)STRIP_TAG(next, TAG1);
+ item = STRIP_MARK(next);
}
return DOES_NOT_EXIST;
}
-uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expectation, uint64_t new_val) {
+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);
if (old_item == NULL) {
// There was not an item in the skiplist that matches the key.
- if (EXPECT_FALSE((int64_t)expectation > 0 || expectation == CAS_EXPECT_EXISTS)) {
+ if (EXPECT_FALSE(expectation != CAS_EXPECT_DOES_NOT_EXIST && expectation != CAS_EXPECT_WHATEVER)) {
TRACE("l1", "sl_cas: the expectation was not met, the skiplist was not changed", 0, 0);
return DOES_NOT_EXIST; // failure
}
- ASSERT(expectation == CAS_EXPECT_DOES_NOT_EXIST || expectation == CAS_EXPECT_WHATEVER);
-
// 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 : (map_key_t)sl->key_type->clone((void *)key);
new_item = node_alloc(n, new_key, new_val);
node_t *pred = preds[0];
- node_t *next = new_item->next[0] = nexts[0];
+ markable_t next = new_item->next[0] = (markable_t)nexts[0];
for (int level = 1; level <= new_item->top_level; ++level) {
- new_item->next[level] = nexts[level];
+ new_item->next[level] = (markable_t)nexts[level];
}
- node_t *other = SYNC_CAS(&pred->next[0], next, new_item);
+ markable_t other = SYNC_CAS(&pred->next[0], next, new_item);
if (other == next) {
TRACE("s3", "sl_cas: successfully inserted item %p at level 0", new_item, 0);
break; // success
}
TRACE("s3", "sl_cas: failed to change pred's link: expected %p found %p", next, other);
if (sl->key_type != NULL) {
- nbd_free(new_key);
+ nbd_free((void *)new_key);
}
nbd_free(new_item);
continue;
}
// 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
// Link <new_item> into <sl> from the bottom up.
for (int level = 1; level <= new_item->top_level; ++level) {
node_t *pred = preds[level];
- node_t *next = nexts[level];
+ markable_t next = (markable_t)nexts[level];
do {
TRACE("s3", "sl_cas: attempting to insert item between %p and %p", pred, next);
- node_t *other = SYNC_CAS(&pred->next[level], next, new_item);
+ markable_t other = SYNC_CAS(&pred->next[level], next, (markable_t)new_item);
if (other == next) {
TRACE("s3", "sl_cas: successfully inserted item %p at level %llu", new_item, level);
break; // success
TRACE("s3", "sl_cas: failed to change pred's link: expected %p found %p", next, other);
find_preds(preds, nexts, new_item->top_level, sl, key, TRUE);
pred = preds[level];
- next = nexts[level];
+ next = (markable_t)nexts[level];
// Update <new_item>'s next pointer
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, TAG1))
+ markable_t old_next = ((volatile node_t *)new_item)->next[level];
+ if (HAS_MARK(old_next))
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);
// Mark and unlink <item> at each level of <sl> from the top down. If multiple threads try to concurrently remove
// the same item only one of them should succeed. Marking the bottom level establishes which of them succeeds.
for (int level = item->top_level; level > 0; --level) {
- node_t *next;
- node_t *old_next = item->next[level];
+ markable_t next;
+ markable_t old_next = item->next[level];
do {
next = old_next;
- old_next = SYNC_CAS(&item->next[level], next, TAG_VALUE(next, TAG1));
- if (IS_TAGGED(old_next, TAG1)) {
+ old_next = SYNC_CAS(&item->next[level], next, MARK_NODE((node_t *)next));
+ if (HAS_MARK(old_next)) {
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, TAG1));
- node_t *other = NULL;
- if ((other = SYNC_CAS(&pred->next[level], item, STRIP_TAG(next, TAG1))) != item) {
+ TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_MARK(next));
+ markable_t other = SYNC_CAS(&pred->next[level], item, STRIP_MARK(next));
+ if (other != (markable_t)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.
- if (other == NULL)
+ if (other == DOES_NOT_EXIST)
continue; // <pred> points past <item> to the end of the list; go on to the next level.
int d = -1;
- if (!IS_TAGGED(other, TAG1)) {
+ if (!HAS_MARK(other)) {
+ map_key_t other_key = GET_NODE(other)->key;
if (EXPECT_TRUE(sl->key_type == NULL)) {
- d = (uint64_t)item->key - (uint64_t)other->key;
+ d = item->key - other_key;
} else {
- d = sl->key_type->cmp(item->key, other->key);
+ d = sl->key_type->cmp((void *)item->key, (void *)other_key);
}
}
if (d > 0) {
}
}
- node_t *next;
- node_t *old_next = item->next[0];
+ markable_t next;
+ markable_t old_next = item->next[0];
do {
next = old_next;
- old_next = SYNC_CAS(&item->next[0], next, TAG_VALUE(next, TAG1));
- if (IS_TAGGED(old_next, TAG1)) {
+ old_next = SYNC_CAS(&item->next[0], next, MARK_NODE((node_t *)next));
+ if (HAS_MARK(old_next)) {
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, TAG1));
- if (SYNC_CAS(&pred->next[0], item, STRIP_TAG(next, TAG1))) {
+ TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_MARK(next));
+ if (SYNC_CAS(&pred->next[0], item, STRIP_MARK(next))) {
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) {
- nbd_defer_free(item->key);
+ nbd_defer_free((void *)item->key);
}
nbd_defer_free(item);
}
void sl_print (skiplist_t *sl) {
for (int level = MAX_LEVEL; level >= 0; --level) {
node_t *item = sl->head;
- if (item->next[level] == NULL)
+ if (item->next[level] == DOES_NOT_EXIST)
continue;
printf("(%d) ", level);
int i = 0;
while (item) {
- node_t *next = item->next[level];
- printf("%s%p ", IS_TAGGED(next, TAG1) ? "*" : "", item);
- item = (node_t *)STRIP_TAG(next, TAG1);
+ markable_t next = item->next[level];
+ printf("%s%p ", HAS_MARK(next) ? "*" : "", item);
+ item = STRIP_MARK(next);
if (i++ > 30) {
printf("...");
break;
node_t *item = sl->head;
int i = 0;
while (item) {
- int is_marked = IS_TAGGED(item->next[0], TAG1);
- printf("%s%p:%p ", is_marked ? "*" : "", item, item->key);
+ int is_marked = HAS_MARK(item->next[0]);
+ printf("%s%p:0x%llx ", is_marked ? "*" : "", item, (uint64_t)item->key);
if (item != sl->head) {
printf("[%d]", item->top_level);
} else {
printf("[HEAD]");
}
for (int level = 1; level <= item->top_level; ++level) {
- node_t *next = (node_t *)STRIP_TAG(item->next[level], TAG1);
- is_marked = IS_TAGGED(item->next[0], TAG1);
+ node_t *next = STRIP_MARK(item->next[level]);
+ is_marked = HAS_MARK(item->next[0]);
printf(" %p%s", next, is_marked ? "*" : "");
- if (item == sl->head && item->next[level] == NULL)
+ if (item == sl->head && item->next[level] == DOES_NOT_EXIST)
break;
}
printf("\n");
fflush(stdout);
- item = (node_t *)STRIP_TAG(item->next[0], TAG1);
+ item = STRIP_MARK(item->next[0]);
if (i++ > 30) {
printf("...\n");
break;
}
}
}
+
+sl_iter_t *sl_iter_begin (skiplist_t *sl, map_key_t key) {
+ sl_iter_t *iter = (sl_iter_t *)nbd_malloc(sizeof(sl_iter_t));
+ if (key != DOES_NOT_EXIST) {
+ find_preds(NULL, &iter->next, 0, sl, key, FALSE);
+ } else {
+ iter->next = GET_NODE(sl->head->next[0]);
+ }
+ return iter;
+}
+
+map_val_t sl_iter_next (sl_iter_t *iter, map_key_t *key_ptr) {
+ assert(iter);
+ node_t *item = iter->next;
+ while (item != NULL && HAS_MARK(item->next[0])) {
+ item = STRIP_MARK(item->next[0]);
+ }
+ if (item == NULL) {
+ iter->next = NULL;
+ return DOES_NOT_EXIST;
+ }
+ iter->next = STRIP_MARK(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);
+}