X-Git-Url: https://pd.if.org/git/?p=nbds;a=blobdiff_plain;f=map%2Fskiplist.c;h=16f7538b9d3f3304d885bf1fb944bea6b2129bb9;hp=66bfb2df4f21ada4ff55a8909ee8bfd2713d2312;hb=f3a053a46bbb4ba460bcff0920b93dfc8263e02e;hpb=f1098084dd54496a61f9a254541190df77edd166

diff --git a/map/skiplist.c b/map/skiplist.c
index 66bfb2d..16f7538 100644
--- a/map/skiplist.c
+++ b/map/skiplist.c
@@ -9,46 +9,39 @@
  * See also Kir Fraser's dissertation "Practical Lock Freedom".
  * www.cl.cam.ac.uk/techreports/UCAM-CL-TR-579.pdf
  *
- * This code is written for the x86 memory-model. The algorithim depends on certain stores and
- * loads being ordered. Be careful, this code won't work correctly on platforms with weaker memory
- * models if you don't add memory barriers in the right places.
+ * I've generalized the data structure to support update operations like set() and CAS() in addition to 
+ * the normal add() and remove() operations.
+ *
+ * Warning: This code is written for the x86 memory-model. The algorithim depends on certain stores 
+ * and loads being ordered. This code won't work correctly on platforms with weaker memory models if
+ * you don't add memory barriers in the right places.
  */
 
 #include <stdio.h>
 #include <string.h>
 
-#define ENABLE_TRACE
-
 #include "common.h"
 #include "runtime.h"
-#include "mlocal.h"
+#include "skiplist.h"
 #include "mem.h"
-#include "tls.h"
 
-// Setting MAX_LEVEL to 0 essentially makes this data structure the Harris-Michael lock-free list
-// (in list.c).
+// 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 {
+typedef struct sl_iter node_t;
+
+struct sl_iter {
     void *key;
     uint64_t val;
     int top_level;
-    struct node *next[];
-} node_t;
+    node_t *next[];
+};
 
 struct sl {
     node_t *head;
-    cmp_fun_t cmp_fun;
-    clone_fun_t clone_fun;
+    const datatype_t *key_type;
 };
 
-static const map_impl_t sl_map_impl = { 
-    (map_alloc_t)sl_alloc, (map_cas_t)sl_cas, (map_get_t)sl_lookup, (map_remove_t)sl_remove, 
-    (map_count_t)sl_count, (map_print_t)sl_print, (map_free_t)sl_free
-};
-
-const map_impl_t *MAP_TYPE_SKIPLIST = &sl_map_impl;
-
 static int random_level (void) {
     unsigned r = nbd_rand();
     if (r & 1)
@@ -72,10 +65,9 @@ static node_t *node_alloc (int level, void *key, uint64_t val) {
     return item;
 }
 
-skiplist_t *sl_alloc (cmp_fun_t cmp_fun, hash_fun_t hash_fun, clone_fun_t clone_fun) {
+skiplist_t *sl_alloc (const datatype_t *key_type) {
     skiplist_t *sl = (skiplist_t *)nbd_malloc(sizeof(skiplist_t));
-    sl->cmp_fun = cmp_fun;
-    sl->clone_fun = clone_fun;
+    sl->key_type = key_type;
     sl->head = node_alloc(MAX_LEVEL, NULL, 0);
     memset(sl->head->next, 0, (MAX_LEVEL+1) * sizeof(skiplist_t *));
     return sl;
@@ -84,7 +76,7 @@ skiplist_t *sl_alloc (cmp_fun_t cmp_fun, hash_fun_t hash_fun, clone_fun_t clone_
 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;
     }
@@ -94,10 +86,10 @@ uint64_t sl_count (skiplist_t *sl) {
     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;
 }
@@ -127,7 +119,7 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
     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
         }
@@ -135,11 +127,11 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
             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);
@@ -150,8 +142,8 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
                 // 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];
@@ -159,7 +151,7 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
 
                     // The thread that completes the unlink should free the memory.
                     if (level == 0) {
-                        if (sl->clone_fun != NULL) {
+                        if (sl->key_type != NULL) {
                             nbd_defer_free((void*)other->key);
                         }
                         nbd_defer_free(other);
@@ -167,7 +159,7 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
                 } 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))
@@ -180,12 +172,12 @@ 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), item->val);
+            TRACE("s4", "find_preds: key %p val %p", STRIP_TAG(item->key, TAG1), item->val);
 
-            if (EXPECT_TRUE(sl->cmp_fun == NULL)) {
+            if (EXPECT_TRUE(sl->key_type == NULL)) {
                 d = (uint64_t)item->key - (uint64_t)key;
             } else {
-                d = sl->cmp_fun(item->key, key);
+                d = sl->key_type->cmp(item->key, key);
             }
 
             if (d >= 0) {
@@ -241,6 +233,17 @@ uint64_t sl_lookup (skiplist_t *sl, void *key) {
     return DOES_NOT_EXIST;
 }
 
+void *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;
+}
+
 uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expectation, uint64_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);
@@ -264,7 +267,7 @@ uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expectation, uint64_t new_v
 
             // 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->clone_fun == NULL) ? key : sl->clone_fun(key);
+            void *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];
@@ -277,7 +280,7 @@ uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expectation, uint64_t new_v
                 break; // success
             }
             TRACE("s3", "sl_cas: failed to change pred's link: expected %p found %p", next, other);
-            if (sl->clone_fun != NULL) {
+            if (sl->key_type != NULL) {
                 nbd_free(new_key);
             }
             nbd_free(new_item);
@@ -334,7 +337,7 @@ uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expectation, uint64_t new_v
             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.
@@ -362,17 +365,17 @@ uint64_t sl_remove (skiplist_t *sl, void *key) {
         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.
@@ -380,11 +383,11 @@ uint64_t sl_remove (skiplist_t *sl, void *key) {
                 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 (EXPECT_TRUE(sl->cmp_fun == NULL)) {
+            if (!IS_TAGGED(other, TAG1)) {
+                if (EXPECT_TRUE(sl->key_type == NULL)) {
                     d = (uint64_t)item->key - (uint64_t)other->key;
                 } else {
-                    d = sl->cmp_fun(item->key, other->key);
+                    d = sl->key_type->cmp(item->key, other->key);
                 }
             }
             if (d > 0) {
@@ -400,8 +403,8 @@ uint64_t sl_remove (skiplist_t *sl, void *key) {
     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;
         }
@@ -409,16 +412,16 @@ uint64_t sl_remove (skiplist_t *sl, void *key) {
     TRACE("s1", "sl_remove: marked item %p removed at level 0", item, 0);
 
     // Atomically swap out the item's value in case another thread is updating the item while we are 
-    // removing it. This establishes which one occurs first, the update or the remove. 
+    // removing it. This establishes which operation occurs first logically, the update or the remove. 
     uint64_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->clone_fun != NULL) {
+        if (sl->key_type != NULL) {
             nbd_defer_free(item->key);
         }
         nbd_defer_free(item);
@@ -435,8 +438,8 @@ void sl_print (skiplist_t *sl) {
         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;
@@ -445,11 +448,10 @@ void sl_print (skiplist_t *sl) {
         printf("\n");
         fflush(stdout);
     }
-
     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);
@@ -457,18 +459,45 @@ void sl_print (skiplist_t *sl) {
             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_start (skiplist_t *sl, void *key) {
+    node_t *item;
+    find_preds(NULL, &item, 0, sl, key, FALSE);
+    return item;
+}
+
+sl_iter_t *sl_iter_next (sl_iter_t *iter) {
+    assert(iter);
+    if (EXPECT_FALSE(!iter))
+        return NULL;
+
+    node_t *next = iter->next[0];
+    while (next != NULL && IS_TAGGED(next->next[0], TAG1)) {
+        next = (node_t *)STRIP_TAG(next->next[0], TAG1);
+    }
+
+    return next;
+}
+
+uint64_t sl_iter_val (sl_iter_t *iter) {
+    return iter->val;
+}
+
+void *sl_iter_key (sl_iter_t *iter) {
+    return iter->key;
+}