use NULL instead of a sentinal node in skiplist and list

[nbds] / struct / list.c

diff --git a/struct/list.c b/struct/list.c
index 40a973599d86360373e4ee561afffc0d3d94fff2..124043d2b4363222c711c644a15a599869b86c51 100644 (file)
--- a/struct/list.c
+++ b/struct/list.c
@@ -20,7 +20,6 @@ typedef struct node {
 
 typedef struct list {
     node_t *head;
 
 typedef struct list {
     node_t *head;

-    node_t *last;

 } list_t;
 
 node_t *node_alloc (uint64_t key, uint64_t value) {
 } list_t;
 
 node_t *node_alloc (uint64_t key, uint64_t value) {


@@ -31,11 +30,10 @@ node_t *node_alloc (uint64_t key, uint64_t value) {
     return item;
 }
 
     return item;
 }
 

-list_t *list_alloc (void) {
+list_t *ll_alloc (void) {

     list_t *list = (list_t *)nbd_malloc(sizeof(list_t));
     list_t *list = (list_t *)nbd_malloc(sizeof(list_t));

-    list->head = node_alloc(0, 0);
-    list->last = node_alloc((uint64_t)-1, 0);
-    list->head->next = list->last;
+    list->head = node_alloc((uint64_t)-1, 0);
+    list->head->next = NULL;

     return list;
 }
 
     return list;
 }
 


@@ -43,11 +41,8 @@ static node_t *find_pred (node_t **pred_ptr, list_t *list, uint64_t key, int hel
     node_t *pred = list->head;
     node_t *item = pred->next;
     TRACE("l3", "find_pred: searching for key %p in list (head is %p)", key, pred);
     node_t *pred = list->head;
     node_t *item = pred->next;
     TRACE("l3", "find_pred: searching for key %p in list (head is %p)", key, pred);

-#ifndef NDEBUG
-    int count = 0;
-#endif

 
 

-    do {
+    while (item != NULL) {

         node_t *next = item->next;
         TRACE("l3", "find_pred: visiting item %p (next %p)", item, next);
         TRACE("l3", "find_pred: key %p", item->key, item->value);
         node_t *next = item->next;
         TRACE("l3", "find_pred: visiting item %p (next %p)", item, next);
         TRACE("l3", "find_pred: key %p", item->key, item->value);


@@ -58,6 +53,8 @@ static node_t *find_pred (node_t **pred_ptr, list_t *list, uint64_t key, int hel
             // Skip over partially removed items.
             if (!help_remove) {
                 item = (node_t *)STRIP_TAG(item->next);
             // Skip over partially removed items.
             if (!help_remove) {
                 item = (node_t *)STRIP_TAG(item->next);

+                if (EXPECT_FALSE(item == NULL))
+                    break;

                 next = item->next;
                 continue;
             }
                 next = item->next;
                 continue;
             }


@@ -66,6 +63,8 @@ static node_t *find_pred (node_t **pred_ptr, list_t *list, uint64_t key, int hel
             node_t *other;
             if ((other = SYNC_CAS(&pred->next, item, STRIP_TAG(next))) == item) {
                 item = (node_t *)STRIP_TAG(next);
             node_t *other;
             if ((other = SYNC_CAS(&pred->next, item, STRIP_TAG(next))) == item) {
                 item = (node_t *)STRIP_TAG(next);

+                if (EXPECT_FALSE(item == NULL))
+                    break;

                 next = item->next;
                 TRACE("l3", "find_pred: unlinked item %p from pred %p", item, pred);
                 TRACE("l3", "find_pred: now item is %p next is %p", item, next);
                 next = item->next;
                 TRACE("l3", "find_pred: unlinked item %p from pred %p", item, pred);
                 TRACE("l3", "find_pred: now item is %p next is %p", item, next);


@@ -73,14 +72,19 @@ static node_t *find_pred (node_t **pred_ptr, list_t *list, uint64_t key, int hel
                 // The thread that completes the unlink should free the memory.
                 nbd_defer_free(other);
             } else {
                 // The thread that completes the unlink should free the memory.
                 nbd_defer_free(other);
             } else {

-                TRACE("l3", "find_pred: lost race to unlink item from pred %p; its link changed to %p", pred, other);
+                TRACE("l3", "find_pred: lost race to unlink from pred %p; its link changed to %p", pred, other);

                 if (IS_TAGGED(other))
                     return find_pred(pred_ptr, list, key, help_remove); // retry
                 item = other;
                 if (IS_TAGGED(other))
                     return find_pred(pred_ptr, list, key, help_remove); // retry
                 item = other;

+                if (EXPECT_FALSE(item == NULL))
+                    break;

                 next = item->next;
             }
         }
 
                 next = item->next;
             }
         }
 

+        if (EXPECT_FALSE(item == NULL))
+            break;
+

         // If we reached the key (or passed where it should be), we found the right predesssor
         if (item->key >= key) {
             TRACE("l3", "find_pred: found pred %p item %p", pred, item);
         // If we reached the key (or passed where it should be), we found the right predesssor
         if (item->key >= key) {
             TRACE("l3", "find_pred: found pred %p item %p", pred, item);


@@ -90,78 +94,83 @@ static node_t *find_pred (node_t **pred_ptr, list_t *list, uint64_t key, int hel
             return item;
         }
 
             return item;
         }
 

-        assert(count++ < 18);

         pred = item;
         item = next;
 
         pred = item;
         item = next;
 

-    } while (1);
+    }
+
+    // <key> is not in the list.
+    if (pred_ptr != NULL) {
+        *pred_ptr = pred;
+    }
+    return NULL;

 }
 
 // Fast find. Do not help unlink partially removed nodes and do not return the found item's predecessor.
 }
 
 // Fast find. Do not help unlink partially removed nodes and do not return the found item's predecessor.

-uint64_t list_lookup (list_t *list, uint64_t key) {
-    TRACE("l3", "list_lookup: searching for key %p in list %p", key, list);
+uint64_t ll_lookup (list_t *list, uint64_t key) {
+    TRACE("l3", "ll_lookup: searching for key %p in list %p", key, list);

     node_t *item = find_pred(NULL, list, key, FALSE);
 
     // If we found an <item> matching the <key> return its value.
     node_t *item = find_pred(NULL, list, key, FALSE);
 
     // If we found an <item> matching the <key> return its value.

-    return (item->key == key) ? item->value : DOES_NOT_EXIST;
+    return (item && item->key == key) ? item->value : DOES_NOT_EXIST;

 }
 
 // Insert the <key>, if it doesn't already exist in the <list>
 }
 
 // Insert the <key>, if it doesn't already exist in the <list>

-uint64_t list_add (list_t *list, uint64_t key, uint64_t value) {
-    TRACE("l3", "list_add: inserting key %p value %p", key, value);
+uint64_t ll_add (list_t *list, uint64_t key, uint64_t value) {
+    TRACE("l3", "ll_add: inserting key %p value %p", key, value);

     node_t *pred;
     node_t *item = NULL;
     do {
         node_t *next = find_pred(&pred, list, key, TRUE);
 
         // If a node matching <key> already exists in the list, return its value.
     node_t *pred;
     node_t *item = NULL;
     do {
         node_t *next = find_pred(&pred, list, key, TRUE);
 
         // If a node matching <key> already exists in the list, return its value.

-        if (next->key == key) {
-            TRACE("l3", "list_add: there is already an item %p (value %p) with the same key", next, next->value);
+        if (next != NULL && next->key == key) {
+            TRACE("l3", "ll_add: there is already an item %p (value %p) with the same key", next, next->value);

             if (EXPECT_FALSE(item != NULL)) { nbd_free(item); }
             return next->value;
         }
 
             if (EXPECT_FALSE(item != NULL)) { nbd_free(item); }
             return next->value;
         }
 

-        TRACE("l3", "list_add: attempting to insert item between %p and %p", pred, next);
+        TRACE("l3", "ll_add: attempting to insert item between %p and %p", pred, next);

         if (EXPECT_TRUE(item == NULL)) { item = node_alloc(key, value); }
         item->next = next;
         node_t *other = SYNC_CAS(&pred->next, next, item);
         if (other == next) {
         if (EXPECT_TRUE(item == NULL)) { item = node_alloc(key, value); }
         item->next = next;
         node_t *other = SYNC_CAS(&pred->next, next, item);
         if (other == next) {

-            TRACE("l3", "list_add: successfully inserted item %p", item, 0);
+            TRACE("l3", "ll_add: successfully inserted item %p", item, 0);

             return DOES_NOT_EXIST; // success
         }
             return DOES_NOT_EXIST; // success
         }

-        TRACE("l3", "list_add: failed to change pred's link: expected %p found %p", next, other);
+        TRACE("l3", "ll_add: failed to change pred's link: expected %p found %p", next, other);

 
     } while (1);
 }
 
 
     } while (1);
 }
 

-uint64_t list_remove (list_t *list, uint64_t key) {
-    TRACE("l3", "list_remove: removing item with key %p from list %p", key, list);
+uint64_t ll_remove (list_t *list, uint64_t key) {
+    TRACE("l3", "ll_remove: removing item with key %p from list %p", key, list);

     node_t *pred;
     node_t *item = find_pred(&pred, list, key, TRUE);
     node_t *pred;
     node_t *item = find_pred(&pred, list, key, TRUE);

-    if (item->key != key) {
-        TRACE("l3", "list_remove: remove failed, an item with a matching key does not exist in the list", 0, 0);
+    if (item == NULL || item->key != key) {
+        TRACE("l3", "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.
     if (EXPECT_FALSE(IS_TAGGED(item->next))) {
         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.
     if (EXPECT_FALSE(IS_TAGGED(item->next))) {

-        TRACE("l3", "list_remove: %p is already marked for removal by another thread", item, 0);
+        TRACE("l3", "ll_remove: %p is already marked for removal by another thread", item, 0);

         return DOES_NOT_EXIST;
     }
     node_t *next = SYNC_FETCH_AND_OR(&item->next, TAG);
     if (EXPECT_FALSE(IS_TAGGED(next))) {
         return DOES_NOT_EXIST;
     }
     node_t *next = SYNC_FETCH_AND_OR(&item->next, TAG);
     if (EXPECT_FALSE(IS_TAGGED(next))) {

-        TRACE("l3", "list_remove: lost race -- %p is already marked for removal by another thread", item, 0);
+        TRACE("l3", "ll_remove: lost race -- %p is already marked for removal by another thread", item, 0);

         return DOES_NOT_EXIST;
     }
 
     uint64_t value = item->value;
 
     // Unlink <item> from the list.
         return DOES_NOT_EXIST;
     }
 
     uint64_t value = item->value;
 
     // Unlink <item> from the list.

-    TRACE("l3", "list_remove: link item's pred %p to it's successor %p", pred, next);
+    TRACE("l3", "ll_remove: link item's pred %p to it's successor %p", pred, next);

     node_t *other;
     if ((other = SYNC_CAS(&pred->next, item, next)) != item) {
     node_t *other;
     if ((other = SYNC_CAS(&pred->next, item, next)) != item) {

-        TRACE("l3", "list_remove: unlink failed; pred's link changed from %p to %p", item, other);
+        TRACE("l3", "ll_remove: unlink failed; pred's link changed from %p to %p", item, other);

         // By marking the item earlier, we logically removed it. It is safe to leave the item.
         // Another thread will finish physically removing it from the list.
         return value;
         // By marking the item earlier, we logically removed it. It is safe to leave the item.
         // Another thread will finish physically removing it from the list.
         return value;


@@ -172,9 +181,9 @@ uint64_t list_remove (list_t *list, uint64_t key) {
     return value;
 }
 
     return value;
 }
 

-void list_print (list_t *list) {
+void ll_print (list_t *list) {

     node_t *item;
     node_t *item;

-    item = list->head;
+    item = list->head->next;

     while (item) {
         printf("0x%llx ", item->key);
         fflush(stdout);
     while (item) {
         printf("0x%llx ", item->key);
         fflush(stdout);


@@ -194,24 +203,21 @@ void list_print (list_t *list) {
 
 static volatile int wait_;
 static long num_threads_;
 
 static volatile int wait_;
 static long num_threads_;

-static list_t *list_;
+static list_t *ll_;

 
 void *worker (void *arg) {
 
 void *worker (void *arg) {

-    int id = (int)(size_t)arg;
-
-    unsigned int rand_seed = id+1;//rdtsc_l();

 
     // Wait for all the worker threads to be ready.
     SYNC_ADD(&wait_, -1);
     do {} while (wait_); 
 
     for (int i = 0; i < NUM_ITERATIONS/num_threads_; ++i) {
 
     // Wait for all the worker threads to be ready.
     SYNC_ADD(&wait_, -1);
     do {} while (wait_); 
 
     for (int i = 0; i < NUM_ITERATIONS/num_threads_; ++i) {

-        int n = rand_r(&rand_seed);
-        int key = (n & 0xF) + 1;
-        if (n & (1 << 8)) {
-            list_add(list_, key, 1);
+        unsigned r = nbd_rand();
+        int key = (r & 0xF);
+        if (r & (1 << 8)) {
+            ll_add(ll_, key, 1);

         } else {
         } else {

-            list_remove(list_, key);
+            ll_remove(ll_, key);

         }
 
         rcu_update();
         }
 
         rcu_update();


@@ -251,7 +257,7 @@ int main (int argc, char **argv) {
         }
     }
 
         }
     }
 

-    list_ = list_alloc();
+    ll_ = ll_alloc();

 
     struct timeval tv1, tv2;
     gettimeofday(&tv1, NULL);
 
     struct timeval tv1, tv2;
     gettimeofday(&tv1, NULL);


@@ -269,9 +275,8 @@ int main (int argc, char **argv) {
 
     gettimeofday(&tv2, NULL);
     int ms = (int)(1000000*(tv2.tv_sec - tv1.tv_sec) + tv2.tv_usec - tv1.tv_usec) / 1000;
 
     gettimeofday(&tv2, NULL);
     int ms = (int)(1000000*(tv2.tv_sec - tv1.tv_sec) + tv2.tv_usec - tv1.tv_usec) / 1000;

+    ll_print(ll_);

     printf("Th:%ld Time:%dms\n", num_threads_, ms);
     printf("Th:%ld Time:%dms\n", num_threads_, ms);

-    list_print(list_);
-    lwt_dump("lwt.out");

 
     return 0;
 }
 
     return 0;
 }