* Harris-Michael lock-free list-based set
* http://www.research.ibm.com/people/m/michael/spaa-2002.pdf
*/
+
#include <stdio.h>
#include <string.h>
#include "common.h"
-#include "mlocal.h"
-#include "nstring.h"
+#include "list.h"
#include "mem.h"
typedef struct node {
- nstring_t *key;
- uint64_t val;
- struct node *next;
+ map_key_t key;
+ map_val_t val;
+ uint64_t next; // next node
} node_t;
+struct ll_iter {
+ node_t *next;
+};
+
struct ll {
node_t *head;
+ const datatype_t *key_type;
};
-static node_t *node_alloc (const void *key_data, uint32_t key_len, uint64_t val) {
+static node_t *node_alloc (map_key_t key, map_val_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->key = key;
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_alloc (const datatype_t *key_type) {
list_t *ll = (list_t *)nbd_malloc(sizeof(list_t));
- ll->head = node_alloc(" ", 0, 0);
- ll->head->next = NULL;
+ ll->key_type = key_type;
+ ll->head = node_alloc(0, 0);
+ ll->head->next = DOES_NOT_EXIST;
return ll;
}
void ll_free (list_t *ll) {
+ node_t *item = (node_t *)(size_t)ll->head->next; // the head can't be tagged
+ while (item) {
+ node_t *next = (node_t *)(size_t)STRIP_TAG(item->next, TAG1);
+ nbd_free(item);
+ item = next;
+ }
+}
+
+uint64_t ll_count (list_t *ll) {
+ uint64_t count = 0;
+ node_t *item = (node_t *)(size_t)ll->head->next;
+ while (item) {
+ if (!IS_TAGGED(item->next, TAG1)) {
+ count++;
+ }
+ item = (node_t *)(size_t)STRIP_TAG(item->next, TAG1);
+ }
+ return count;
}
-static int find_pred (node_t **pred_ptr, node_t **item_ptr, list_t *ll, const void *key_data, uint32_t key_len, int help_remove) {
+static int find_pred (node_t **pred_ptr, node_t **item_ptr, list_t *ll, map_key_t key, int help_remove) {
node_t *pred = ll->head;
- node_t *item = pred->next;
- TRACE("l2", "find_pred: searching for key %p in ll (head is %p)", key_data, pred);
+ node_t *item = (node_t *)(size_t)pred->next;
+ TRACE("l2", "find_pred: searching for key %p in list (head is %p)", key, pred);
while (item != NULL) {
- node_t *next = item->next;
+ uint64_t next = item->next;
// 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 *)(size_t)STRIP_TAG(item->next, TAG1);
if (EXPECT_FALSE(item == NULL))
break;
TRACE("l3", "find_pred: skipping marked item %p (next is %p)", item, next);
}
// Unlink logically removed items.
- node_t *other;
TRACE("l3", "find_pred: unlinking marked item %p next is %p", item, next);
- if ((other = SYNC_CAS(&pred->next, item, STRIP_TAG(next))) == item) {
+
+ uint64_t other = SYNC_CAS(&pred->next, (uint64_t)(size_t)item, STRIP_TAG(next, TAG1));
+ if (other == (uint64_t)(size_t)item) {
TRACE("l2", "find_pred: unlinked item %p from pred %p", item, pred);
- item = (node_t *)STRIP_TAG(next);
- if (EXPECT_FALSE(item == NULL))
- break;
- next = item->next;
+ item = (node_t *)(size_t)STRIP_TAG(next, TAG1);
+ next = (item != NULL) ? item->next : DOES_NOT_EXIST;
TRACE("l3", "find_pred: now current item is %p next is %p", item, next);
// The thread that completes the unlink should free the memory.
- node_defer_free(other);
+ if (ll->key_type != NULL) {
+ nbd_defer_free((void *)(size_t)((node_t *)(size_t)other)->key);
+ }
+ nbd_defer_free(((node_t *)(size_t)other));
} else {
TRACE("l2", "find_pred: lost a race to unlink item %p from pred %p", item, pred);
TRACE("l2", "find_pred: pred's link changed to %p", other, 0);
- if (IS_TAGGED(other))
- return find_pred(pred_ptr, item_ptr, ll, key_data, key_len, help_remove); // retry
- item = other;
- if (EXPECT_FALSE(item == NULL))
- break;
- next = item->next;
+ if (IS_TAGGED(other, TAG1))
+ return find_pred(pred_ptr, item_ptr, ll, key, help_remove); // retry
+ item = (node_t *)(size_t)other;
+ next = (item != NULL) ? item->next : DOES_NOT_EXIST;
}
}
break;
TRACE("l3", "find_pred: visiting item %p (next is %p)", item, next);
- TRACE("l4", "find_pred: key %p val %p", STRIP_TAG(item->key), item->val);
+ TRACE("l4", "find_pred: key %p val %p", item->key, item->val);
- // A tagged key is an integer, otherwise it is a pointer to a string
int d;
- if (IS_TAGGED(item->key)) {
- d = (STRIP_TAG(item->key) - (uint64_t)key_data);
+ if (EXPECT_TRUE(ll->key_type == NULL)) {
+ d = (uint64_t)item->key - (uint64_t)key;
} else {
- int item_key_len = item->key->len;
- int len = (key_len < item_key_len) ? key_len : item_key_len;
- d = memcmp(item->key->data, key_data, len);
- if (d == 0) { d = item_key_len - key_len; }
+ d = ll->key_type->cmp((void *)(size_t)item->key, (void *)(size_t)key);
+ }
+
+ if (next != DOES_NOT_EXIST && ((node_t *)next)->key < item->key) {
+ lwt_halt();
+ assert(0);
}
// If we reached the key (or passed where it should be), we found the right predesssor
TRACE("l2", "find_pred: found matching item %p in list, pred is %p", item, pred);
return TRUE;
}
- TRACE("l2", "find_pred: found proper place for key %p in list, pred is %p", key_data, pred);
+ TRACE("l2", "find_pred: found proper place for key %p in list, pred is %p", key, pred);
return FALSE;
}
pred = item;
- item = next;
+ item = (node_t *)(size_t)next;
}
// <key> is not in <ll>.
}
// 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("l1", "ll_lookup: searching for key %p in list %p", key_data, ll);
+map_val_t ll_lookup (list_t *ll, map_key_t key) {
+ TRACE("l1", "ll_lookup: searching for key %p in list %p", key, ll);
node_t *item;
- int found = find_pred(NULL, &item, ll, key_data, key_len, FALSE);
+ int found = find_pred(NULL, &item, ll, key, FALSE);
// If we found an <item> matching the key return its value.
if (found) {
- uint64_t val = item->val;
+ map_val_t val = item->val;
if (val != DOES_NOT_EXIST) {
TRACE("l1", "ll_lookup: found item %p. val %p. returning item", item, item->val);
return val;
return DOES_NOT_EXIST;
}
-uint64_t ll_cas (list_t *ll, const void *key_data, uint32_t key_len, uint64_t expectation, uint64_t new_val) {
- TRACE("l1", "ll_cas: key %p list %p", key_data, ll);
+map_val_t ll_cas (list_t *ll, map_key_t key, map_val_t expectation, map_val_t new_val) {
+ TRACE("l1", "ll_cas: key %p list %p", key, ll);
TRACE("l1", "ll_cas: expectation %p new value %p", expectation, new_val);
ASSERT((int64_t)new_val > 0);
do {
node_t *pred, *old_item;
- if (!find_pred(&pred, &old_item, ll, key_data, key_len, TRUE)) {
+ int found = find_pred(&pred, &old_item, ll, key, TRUE);
+ if (!found) {
// There was not an item in the list that matches the key.
if (EXPECT_FALSE((int64_t)expectation > 0 || expectation == CAS_EXPECT_EXISTS)) {
// Create a new item and insert it into the list.
TRACE("l2", "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 = old_item;
- node_t *other = SYNC_CAS(&pred->next, next, new_item);
+ map_key_t new_key = (ll->key_type == NULL)
+ ? key
+ : (map_key_t)(size_t)ll->key_type->clone((void *)(size_t)key);
+ node_t *new_item = node_alloc(new_key, new_val);
+ uint64_t next = new_item->next = (uint64_t)(size_t)old_item;
+ uint64_t other = SYNC_CAS(&pred->next, next, new_item);
if (other == next) {
TRACE("l1", "ll_cas: successfully inserted new item %p", new_item, 0);
return DOES_NOT_EXIST; // success
// Lost a race. Failed to insert the new item into the list.
TRACE("l1", "ll_cas: lost a race. CAS failed. expected pred's link to be %p but found %p", next, other);
- node_free(new_item);
+ if (ll->key_type != NULL) {
+ nbd_free((void *)(size_t)new_key);
+ }
+ nbd_free(new_item);
continue; // retry
}
// Found an item in the list 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("l1", "ll_cas: the CAS succeeded. updated the value of the item", 0, 0);
return ret_val; // success
} while (1);
}
-uint64_t ll_remove (list_t *ll, const void *key_data, uint32_t key_len) {
- TRACE("l1", "ll_remove: removing item with key %p from list %p", key_data, ll);
+map_val_t ll_remove (list_t *ll, map_key_t key) {
+ TRACE("l1", "ll_remove: removing item with key %p from list %p", key, ll);
node_t *pred;
node_t *item;
- int found = find_pred(&pred, &item, ll, key_data, key_len, TRUE);
+ int found = find_pred(&pred, &item, ll, key, TRUE);
if (!found) {
TRACE("l1", "ll_remove: remove failed, an item with a matching key does not exist in the list", 0, 0);
return DOES_NOT_EXIST;
}
- // Mark <item> removed. This must be atomic. If multiple threads try to remove the same item
- // only one of them should succeed.
- node_t *next;
- node_t *old_next = item->next;
+ // Mark <item> removed. If multiple threads try to remove the same item only one of them should succeed.
+ uint64_t next;
+ uint64_t old_next = item->next;
do {
- next = old_next;
- old_next = SYNC_CAS(&item->next, next, TAG_VALUE(next));
- if (IS_TAGGED(old_next)) {
+ next = old_next;
+ old_next = SYNC_CAS(&item->next, next, TAG_VALUE(next, TAG1));
+ if (IS_TAGGED(old_next, TAG1)) {
TRACE("l1", "ll_remove: lost a race -- %p is already marked for removal by another thread", item, 0);
return DOES_NOT_EXIST;
}
} while (next != old_next);
TRACE("l2", "ll_remove: logically removed item %p", item, 0);
- ASSERT(IS_TAGGED(item->next));
+ ASSERT(IS_TAGGED(((volatile node_t *)item)->next, TAG1));
- // This has to be an atomic swap in case another thread is updating the item while we are removing it.
- uint64_t val = SYNC_SWAP(&item->val, 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.
+ map_val_t val = SYNC_SWAP(&item->val, DOES_NOT_EXIST);
TRACE("l2", "ll_remove: replaced item's val %p with DOES_NOT_EXIT", val, 0);
// 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("l2", "ll_remove: unlink the item by linking its pred %p to its successor %p", pred, next);
- node_t *other;
- if ((other = SYNC_CAS(&pred->next, item, next)) != item) {
+ uint64_t other;
+ if ((other = SYNC_CAS(&pred->next, (uint64_t)(size_t)item, next)) != (uint64_t)(size_t)item) {
TRACE("l1", "ll_remove: unlink failed; pred's link changed from %p to %p", item, other);
return val;
}
// The thread that completes the unlink should free the memory.
- node_defer_free(item);
+ if (ll->key_type != NULL) {
+ nbd_defer_free((void *)(size_t)item->key);
+ }
+ nbd_defer_free(item);
TRACE("l1", "ll_remove: successfully unlinked item %p from the list", item, 0);
return val;
}
void ll_print (list_t *ll) {
- node_t *item;
- item = ll->head->next;
- while (item) {
- node_t *next = item->next;
- if (IS_TAGGED(item)) {
+ uint64_t next = ll->head->next;
+ int i = 0;
+ while (next != DOES_NOT_EXIST) {
+ if (IS_TAGGED(next, TAG1)) {
printf("*");
}
- printf("%p:", item);
- if (IS_TAGGED(item->key)) {
- printf("0x%llx ", STRIP_TAG(item->key));
- } else {
- printf("%s ", (char *)item->key->data);
- }
+ node_t *item = (node_t *)(size_t)STRIP_TAG(next, TAG1);
+ if (item == NULL)
+ break;
+ printf("%p:0x%llx ", item, item->key);
fflush(stdout);
- item = (node_t *)STRIP_TAG(next);
+ if (i++ > 30) {
+ printf("...");
+ break;
+ }
+ next = item->next;
}
printf("\n");
}
+
+ll_iter_t *ll_iter_begin (list_t *ll, map_key_t key) {
+ ll_iter_t *iter = (ll_iter_t *)nbd_malloc(sizeof(ll_iter_t));
+ find_pred(NULL, &iter->next, ll, key, FALSE);
+ return iter;
+}
+
+map_val_t ll_iter_next (ll_iter_t *iter, map_key_t *key_ptr) {
+ assert(iter);
+ node_t *item = iter->next;
+ while (item != NULL && IS_TAGGED(item->next, TAG1)) {
+ item = (node_t *)(size_t)STRIP_TAG(item->next, TAG1);
+ }
+ if (item == NULL) {
+ iter->next = NULL;
+ return DOES_NOT_EXIST;
+ }
+ iter->next = (node_t *)(size_t)STRIP_TAG(item->next, TAG1);
+ if (key_ptr != NULL) {
+ *key_ptr = item->key;
+ }
+ return item->val;
+}
+
+void ll_iter_free (ll_iter_t *iter) {
+ nbd_free(iter);
+}