#define dbg_printf(args...)
#endif
-#define CHAIN_LEN_TARGET 4
-#define CHAIN_LEN_RESIZE_THRESHOLD 16
+#define CHAIN_LEN_TARGET 1
+#define CHAIN_LEN_RESIZE_THRESHOLD 2
#ifndef max
#define max(a, b) ((a) > (b) ? (a) : (b))
struct rcu_table {
unsigned long size; /* always a power of 2 */
unsigned long resize_target;
+ int resize_initiated;
struct rcu_head head;
struct rcu_ht_node *tbl[0];
};
{
if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
ht_resize_lazy(ht, t,
- log2_u32(chain_len - CHAIN_LEN_TARGET));
+ log2_u32(chain_len - CHAIN_LEN_TARGET - 1));
}
static
return v;
}
+/*
+ * Remove all logically deleted nodes from a bucket up to a certain node key.
+ */
+static
+void _ht_gc_bucket(struct rcu_ht_node *dummy, struct rcu_ht_node *node)
+{
+ struct rcu_ht_node *iter_prev, *iter, *next;
+
+ for (;;) {
+ iter_prev = dummy;
+ /* We can always skip the dummy node initially */
+ iter = rcu_dereference(iter_prev->next);
+ assert(iter_prev->reverse_hash <= node->reverse_hash);
+ for (;;) {
+ if (unlikely(!iter))
+ return;
+ if (clear_flag(iter)->reverse_hash > node->reverse_hash)
+ return;
+ next = rcu_dereference(clear_flag(iter)->next);
+ if (is_removed(next))
+ break;
+ iter_prev = iter;
+ iter = next;
+ }
+ assert(!is_removed(iter));
+ (void) uatomic_cmpxchg(&iter_prev->next, iter, clear_flag(next));
+ }
+}
+
static
-void _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
+int _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node,
+ int unique)
{
- struct rcu_ht_node *iter_prev = NULL, *iter = NULL;
+ struct rcu_ht_node *iter_prev, *dummy, *iter, *next;
if (!t->size)
- return;
+ return 0;
for (;;) {
uint32_t chain_len = 0;
+ /*
+ * iter_prev points to the non-removed node prior to the
+ * insert location.
+ */
iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
- assert(iter_prev);
+ /* We can always skip the dummy node initially */
+ iter = rcu_dereference(iter_prev->next);
assert(iter_prev->reverse_hash <= node->reverse_hash);
for (;;) {
- iter = clear_flag(rcu_dereference(iter_prev->next));
if (unlikely(!iter))
- break;
- if (iter->reverse_hash < node->reverse_hash)
- break;
- iter_prev = iter;
- check_resize(ht, t, ++chain_len);
+ goto insert;
+ if (clear_flag(iter)->reverse_hash > node->reverse_hash)
+ goto insert;
+ next = rcu_dereference(clear_flag(iter)->next);
+ if (is_removed(next))
+ goto gc_node;
+ /* Only account for identical reverse hash once */
+ if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash)
+ check_resize(ht, t, ++chain_len);
+ iter_prev = clear_flag(iter);
+ iter = next;
}
- /* add in iter_prev->next */
- if (is_removed(iter))
- continue;
- assert(node != iter);
- node->next = iter;
+ insert:
+ assert(node != clear_flag(iter));
+ assert(!is_removed(iter_prev));
assert(iter_prev != node);
- if (uatomic_cmpxchg(&iter_prev->next, iter, node) != iter)
- continue;
- break;
+ node->next = iter;
+ if (uatomic_cmpxchg(&iter_prev->next, iter,
+ node) != iter)
+ continue; /* retry */
+ else
+ goto gc_end;
+ gc_node:
+ assert(!is_removed(iter));
+ (void) uatomic_cmpxchg(&iter_prev->next, iter, clear_flag(next));
+ /* retry */
}
+gc_end:
+ /* Garbage collect logically removed nodes in the bucket */
+ dummy = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
+ _ht_gc_bucket(dummy, node);
+ return 0;
}
static
int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
{
- struct rcu_ht_node *iter_prev, *iter, *next, *old;
- unsigned long chain_len;
- int found, ret = 0;
+ struct rcu_ht_node *dummy, *next, *old;
int flagged = 0;
-retry:
- chain_len = 0;
- found = 0;
- iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
- assert(iter_prev);
- assert(iter_prev->reverse_hash <= node->reverse_hash);
- for (;;) {
- iter = clear_flag(rcu_dereference(iter_prev->next));
- if (unlikely(!iter))
- break;
- if (iter->reverse_hash < node->reverse_hash)
- break;
- if (iter == node) {
- found = 1;
- break;
- }
- iter_prev = iter;
- }
- if (!found) {
- ret = -ENOENT;
- goto end;
- }
- next = rcu_dereference(iter->next);
- if (!flagged) {
- if (is_removed(next)) {
- ret = -ENOENT;
+ /* logically delete the node */
+ old = rcu_dereference(node->next);
+ do {
+ next = old;
+ if (is_removed(next))
goto end;
- }
- /* set deletion flag */
- if ((old = uatomic_cmpxchg(&iter->next, next,
- flag_removed(next))) != next) {
- if (old == flag_removed(next)) {
- ret = -ENOENT;
- goto end;
- } else {
- goto retry;
- }
- }
- flagged = 1;
- }
+ assert(!node->dummy);
+ old = uatomic_cmpxchg(&node->next, next,
+ flag_removed(next));
+ } while (old != next);
+
+ /* We performed the (logical) deletion. */
+ flagged = 1;
+
/*
- * Remove the element from the list. Retry if there has been a
- * concurrent add (there cannot be a concurrent delete, because
- * we won the deletion flag cmpxchg).
+ * Ensure that the node is not visible to readers anymore: lookup for
+ * the node, and remove it (along with any other logically removed node)
+ * if found.
*/
- if (uatomic_cmpxchg(&iter_prev->next, iter, clear_flag(next)) != iter)
- goto retry;
+ dummy = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
+ _ht_gc_bucket(dummy, node);
end:
- return ret;
+ /*
+ * Only the flagging action indicated that we (and no other)
+ * removed the node from the hash.
+ */
+ if (flagged) {
+ assert(is_removed(rcu_dereference(node->next)));
+ return 0;
+ } else
+ return -ENOENT;
}
static
t->tbl[i]->dummy = 1;
t->tbl[i]->hash = i;
t->tbl[i]->reverse_hash = bit_reverse_ulong(i);
- _ht_add(ht, t, t->tbl[i]);
+ (void) _ht_add(ht, t, t->tbl[i], 0);
}
t->resize_target = t->size = end;
+ t->resize_initiated = 0;
}
struct rcu_ht *ht_new(ht_hash_fct hash_fct,
for (;;) {
if (unlikely(!node))
break;
- if (node->reverse_hash > reverse_hash) {
+ if (unlikely(node->reverse_hash > reverse_hash)) {
node = NULL;
break;
}
if (!ht->compare_fct(node->key, node->key_len, key, key_len)) {
- if (is_removed(rcu_dereference(node->next)))
- node = NULL;
- break;
+ if (likely(!is_removed(rcu_dereference(node->next)))
+ && likely(!node->dummy))
+ break;
}
node = clear_flag(rcu_dereference(node->next));
}
+ assert(!node || !node->dummy);
return node;
}
node->reverse_hash = bit_reverse_ulong((unsigned long) node->hash);
t = rcu_dereference(ht->t);
- _ht_add(ht, t, node);
+ (void) _ht_add(ht, t, node, 0);
+}
+
+int ht_add_unique(struct rcu_ht *ht, struct rcu_ht_node *node)
+{
+ struct rcu_table *t;
+
+ node->hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
+ node->reverse_hash = bit_reverse_ulong((unsigned long) node->hash);
+
+ t = rcu_dereference(ht->t);
+ return _ht_add(ht, t, node, 1);
}
int ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node)
if (!node->dummy)
return -EPERM;
node = node->next;
+ assert(!is_removed(node));
} while (node);
/* Internal sanity check: all nodes left should be dummy */
for (i = 0; i < t->size; i++) {
return ret;
}
+void ht_count_nodes(struct rcu_ht *ht,
+ unsigned long *count,
+ unsigned long *removed)
+{
+ struct rcu_table *t;
+ struct rcu_ht_node *node, *next;
+
+ *count = 0;
+ *removed = 0;
+
+ t = rcu_dereference(ht->t);
+ /* Check that the table is empty */
+ node = rcu_dereference(t->tbl[0]);
+ do {
+ next = rcu_dereference(node->next);
+ if (is_removed(next)) {
+ assert(!node->dummy);
+ (*removed)++;
+ } else if (!node->dummy)
+ (*count)++;
+ node = clear_flag(next);
+ } while (node);
+}
+
static
void ht_free_table_cb(struct rcu_head *head)
{
target_size = resize_target_update(t, growth);
if (t->size < target_size) {
+ CMM_STORE_SHARED(t->resize_initiated, 1);
pthread_mutex_lock(&ht->resize_mutex);
_do_ht_resize(ht);
pthread_mutex_unlock(&ht->resize_mutex);
unsigned long target_size;
target_size = resize_target_update(t, growth);
- if (t->size < target_size) {
+ if (!CMM_LOAD_SHARED(t->resize_initiated) && t->size < target_size) {
work = malloc(sizeof(*work));
work->ht = ht;
ht->ht_call_rcu(&work->head, do_resize_cb);
+ CMM_STORE_SHARED(t->resize_initiated, 1);
}
}
projects / urcu.git / blobdiff