X-Git-Url: https://pd.if.org/git/?p=nbds;a=blobdiff_plain;f=map%2Fskiplist.c;h=5366d91adae9bcef2c5caa6f91cd95f6c61c8b47;hp=e81a89680154e3ef3b6e55edd9f75c17efe85f89;hb=4ae7c1069667d8f067258d89676126f9b44226d6;hpb=8c48c212e119ba28b0666c9ec3faa97cbd11ca7a diff --git a/map/skiplist.c b/map/skiplist.c index e81a896..5366d91 100644 --- a/map/skiplist.c +++ b/map/skiplist.c @@ -32,7 +32,7 @@ typedef struct node { map_key_t key; map_val_t val; int top_level; - uint64_t next[]; + markable_t next[]; } node_t; struct sl_iter { @@ -44,6 +44,19 @@ struct sl { const datatype_t *key_type; }; +// Marking the 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) @@ -76,25 +89,25 @@ skiplist_t *sl_alloc (const datatype_t *key_type) { } void sl_free (skiplist_t *sl) { - node_t *item = (node_t *)(size_t)sl->head->next[0]; + node_t *item = GET_NODE(sl->head->next[0]); while (item) { - node_t *next = (node_t *)(size_t)STRIP_TAG(item->next[0], TAG1); + node_t *next = STRIP_MARK(item->next[0]); if (sl->key_type != NULL) { - nbd_free((void *)(size_t)item->key); + nbd_free((void *)item->key); } nbd_free(item); item = next; } } -uint64_t sl_count (skiplist_t *sl) { - uint64_t count = 0; - node_t *item = (node_t *)(size_t)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 *)(size_t)STRIP_TAG(item->next[0], TAG1); + item = STRIP_MARK(item->next[0]); } return count; } @@ -123,20 +136,21 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl // Traverse the levels of from the top level to the bottom for (int level = start_level; level >= 0; --level) { TRACE("s3", "find_preds: level %llu", level, 0); - item = (node_t *)pred->next[level]; - if (EXPECT_FALSE(IS_TAGGED((uint64_t)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) { - uint64_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 *)(size_t)STRIP_TAG(next, TAG1); + item = STRIP_MARK(next); if (EXPECT_FALSE(item == NULL)) break; next = item->next[level]; @@ -146,25 +160,26 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl // Unlink logically removed items. TRACE("s3", "find_preds: unlinking marked item %p; next is 0x%llx", item, next); - uint64_t other = SYNC_CAS(&pred->next[level], (uint64_t)(size_t)item, STRIP_TAG(next, TAG1)); - if (other == (uint64_t)(size_t)item) { - item = (node_t *)(size_t)STRIP_TAG(next, TAG1); + 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 *)(size_t)((node_t *)(size_t)other)->key); + nbd_defer_free((void *)unlinked->key); } - nbd_defer_free(((node_t *)(size_t)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 = (node_t *)(size_t)other; + item = GET_NODE(other); next = (item != NULL) ? item->next[level] : DOES_NOT_EXIST; } } @@ -173,12 +188,12 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl 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((void *)(size_t)item->key, (void *)(size_t)key); + d = sl->key_type->cmp((void *)item->key, (void *)key); } if (d >= 0) { @@ -187,7 +202,7 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl } pred = item; - item = (node_t *)(size_t)next; + item = GET_NODE(next); } // The cast to unsigned is for the case when n is -1. @@ -236,12 +251,12 @@ map_val_t sl_lookup (skiplist_t *sl, map_key_t key) { } map_key_t sl_min_key (skiplist_t *sl) { - node_t *item = (node_t *)(size_t)sl->head->next[0]; + node_t *item = GET_NODE(sl->head->next[0]); while (item != NULL) { - uint64_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 *)(size_t)STRIP_TAG(next, TAG1); + item = STRIP_MARK(next); } return DOES_NOT_EXIST; } @@ -269,23 +284,21 @@ map_val_t sl_cas (skiplist_t *sl, map_key_t key, map_val_t expectation, map_val_ // First insert into the bottom level. TRACE("s3", "sl_cas: attempting to insert item between %p and %p", preds[0], nexts[0]); - map_key_t new_key = (sl->key_type == NULL) - ? key - : (map_key_t)(size_t)sl->key_type->clone((void *)(size_t)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]; - uint64_t next = new_item->next[0] = (uint64_t)(size_t)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] = (uint64_t)(size_t)nexts[level]; + new_item->next[level] = (markable_t)nexts[level]; } - uint64_t other = SYNC_CAS(&pred->next[0], next, (uint64_t)(size_t)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((void *)(size_t)new_key); + nbd_free((void *)new_key); } nbd_free(new_item); continue; @@ -324,10 +337,10 @@ map_val_t sl_cas (skiplist_t *sl, map_key_t key, map_val_t expectation, map_val_ // Link into from the bottom up. for (int level = 1; level <= new_item->top_level; ++level) { node_t *pred = preds[level]; - uint64_t next = (uint64_t)(size_t)nexts[level]; + markable_t next = (markable_t)nexts[level]; do { TRACE("s3", "sl_cas: attempting to insert item between %p and %p", pred, next); - uint64_t other = SYNC_CAS(&pred->next[level], next, (uint64_t)(size_t)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 @@ -335,13 +348,13 @@ map_val_t sl_cas (skiplist_t *sl, map_key_t key, map_val_t expectation, map_val_ 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 = (uint64_t)(size_t)nexts[level]; + next = (markable_t)nexts[level]; // Update 's next pointer do { // There in no need to continue linking in the item if another thread removed it. - uint64_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. @@ -365,21 +378,21 @@ map_val_t sl_remove (skiplist_t *sl, map_key_t key) { // Mark and unlink at each level of 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) { - uint64_t next; - uint64_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)); - uint64_t other = SYNC_CAS(&pred->next[level], (uint64_t)(size_t)item, STRIP_TAG(next, TAG1)); - if (other != (uint64_t)(size_t)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. @@ -387,12 +400,12 @@ map_val_t sl_remove (skiplist_t *sl, map_key_t key) { continue; // points past to the end of the list; go on to the next level. int d = -1; - if (!IS_TAGGED(other, TAG1)) { - map_key_t other_key = ((node_t *)(size_t)other)->key; + 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((void *)(size_t)item->key, (void *)(size_t)other_key); + d = sl->key_type->cmp((void *)item->key, (void *)other_key); } } if (d > 0) { @@ -404,12 +417,12 @@ map_val_t sl_remove (skiplist_t *sl, map_key_t key) { } } - uint64_t next; - uint64_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; } @@ -422,12 +435,12 @@ map_val_t sl_remove (skiplist_t *sl, map_key_t key) { 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((void *)(size_t)item->key); + nbd_defer_free((void *)item->key); } nbd_defer_free(item); } @@ -442,9 +455,9 @@ void sl_print (skiplist_t *sl) { printf("(%d) ", level); int i = 0; while (item) { - uint64_t next = item->next[level]; - printf("%s%p ", IS_TAGGED(next, TAG1) ? "*" : "", item); - item = (node_t *)(size_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; @@ -456,23 +469,23 @@ void sl_print (skiplist_t *sl) { node_t *item = sl->head; int i = 0; while (item) { - int is_marked = IS_TAGGED(item->next[0], TAG1); - printf("%s%p:0x%llx ", is_marked ? "*" : "", item, (uint64_t)(size_t)item->key); + int is_marked = HAS_MARK(item->next[0]); + printf("%s%p:0x%llx ", is_marked ? "*" : "", item, (map_key_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 *)(size_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] == DOES_NOT_EXIST) break; } printf("\n"); fflush(stdout); - item = (node_t *)(size_t)STRIP_TAG(item->next[0], TAG1); + item = STRIP_MARK(item->next[0]); if (i++ > 30) { printf("...\n"); break; @@ -489,14 +502,14 @@ sl_iter_t *sl_iter_begin (skiplist_t *sl, map_key_t key) { 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 && IS_TAGGED(item->next[0], TAG1)) { - item = (node_t *)(size_t)STRIP_TAG(item->next[0], TAG1); + 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 = (node_t *)(size_t)STRIP_TAG(item->next[0], TAG1); + iter->next = STRIP_MARK(item->next[0]); if (key_ptr != NULL) { *key_ptr = item->key; }