rculfhash: add missing clear flag in gc

[urcu.git] / rculfhash.c

diff --git a/rculfhash.c b/rculfhash.c
index 86b93b2aa54914f3bb9f6d0cec46dd8f2098c564..0c433e54050ea0ba311b91114f6c58b26222629e 100644 (file)
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -53,6 +53,11 @@
 #define max(a, b)      ((a) > (b) ? (a) : (b))
 #endif
 
+/*
+ * The removed flag needs to be updated atomically with the pointer.
+ * The dummy flag does not require to be updated atomically with the
+ * pointer, but it is added as a pointer low bit flag to save space.
+ */
 #define REMOVED_FLAG           (1UL << 0)
 #define DUMMY_FLAG             (1UL << 1)
 #define FLAGS_MASK             ((1UL << 2) - 1)
@@ -242,7 +247,7 @@ void _ht_gc_bucket(struct rcu_ht_node *dummy, struct rcu_ht_node *node)
                        next = rcu_dereference(clear_flag(iter)->p.next);
                        if (is_removed(next))
                                break;
-                       iter_prev = iter;
+                       iter_prev = clear_flag(iter);
                        iter = next;
                }
                assert(!is_removed(iter));
@@ -263,7 +268,6 @@ struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t,
        unsigned long hash;
 
        if (!t->size) {
-               assert(node->p.dummy);
                assert(dummy);
                node->p.next = flag_dummy(NULL);
                return node;    /* Initial first add (head) */
@@ -289,7 +293,7 @@ struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t,
                        if (is_removed(next))
                                goto gc_node;
                        if (unique
-                           && !clear_flag(iter)->p.dummy
+                           && !is_dummy(next)
                            && !ht->compare_fct(node->key, node->key_len,
                                                clear_flag(iter)->key,
                                                clear_flag(iter)->key_len))
@@ -305,9 +309,9 @@ struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t,
                assert(!is_removed(iter_prev));
                assert(iter_prev != node);
                if (!dummy)
-                       node->p.next = iter;
+                       node->p.next = clear_flag(iter);
                else
-                       node->p.next = flag_dummy(iter);
+                       node->p.next = flag_dummy(clear_flag(iter));
                if (is_dummy(iter))
                        new_node = flag_dummy(node);
                else
@@ -346,7 +350,7 @@ int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
                next = old;
                if (is_removed(next))
                        goto end;
-               assert(!node->p.dummy);
+               assert(!is_dummy(next));
                old = uatomic_cmpxchg(&node->p.next, next,
                                      flag_removed(next));
        } while (old != next);
@@ -386,7 +390,6 @@ void init_table(struct rcu_ht *ht, struct rcu_table *t,
                if (i != 0 && !(i & (i - 1)))
                        t->size = i;
                t->tbl[i] = calloc(1, sizeof(struct _rcu_ht_node));
-               t->tbl[i]->p.dummy = 1;
                t->tbl[i]->p.reverse_hash = bit_reverse_ulong(i);
                (void) _ht_add(ht, t, t->tbl[i], 0, 1);
        }
@@ -423,7 +426,7 @@ struct rcu_ht *ht_new(ht_hash_fct hash_fct,
 struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
 {
        struct rcu_table *t;
-       struct rcu_ht_node *node;
+       struct rcu_ht_node *node, *next;
        unsigned long hash, reverse_hash;
 
        hash = ht->hash_fct(key, key_len, ht->hash_seed);
@@ -438,14 +441,15 @@ struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
                        node = NULL;
                        break;
                }
-               if (likely(!is_removed(rcu_dereference(node->p.next)))
-                   && !node->p.dummy
+               next = rcu_dereference(node->p.next);
+               if (likely(!is_removed(next))
+                   && !is_dummy(next)
                    && likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
                                break;
                }
-               node = clear_flag(rcu_dereference(node->p.next));
+               node = clear_flag(next);
        }
-       assert(!node || !node->p.dummy);
+       assert(!node || !is_dummy(rcu_dereference(node->p.next)));
        return node;
 }
 
@@ -492,14 +496,14 @@ int ht_delete_dummy(struct rcu_ht *ht)
        /* Check that the table is empty */
        node = t->tbl[0];
        do {
-               if (!node->p.dummy)
+               node = clear_flag(node)->p.next;
+               if (!is_dummy(node))
                        return -EPERM;
-               node = node->p.next;
                assert(!is_removed(node));
        } while (clear_flag(node));
        /* Internal sanity check: all nodes left should be dummy */
        for (i = 0; i < t->size; i++) {
-               assert(t->tbl[i]->p.dummy);
+               assert(is_dummy(t->tbl[i]->p.next));
                free(t->tbl[i]);
        }
        return 0;
@@ -540,9 +544,9 @@ void ht_count_nodes(struct rcu_ht *ht,
        do {
                next = rcu_dereference(node->p.next);
                if (is_removed(next)) {
-                       assert(!node->p.dummy);
+                       assert(!is_dummy(next));
                        (*removed)++;
-               } else if (!node->p.dummy)
+               } else if (!is_dummy(next))
                        (*count)++;
                node = clear_flag(next);
        } while (node);