#ifndef _URCU_RCULFHASH_H
#define _URCU_RCULFHASH_H
+/*
+ * urcu/rculfhash.h
+ *
+ * Userspace RCU library - Lock-Free RCU Hash Table
+ *
+ * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * Include this file _after_ including your URCU flavor.
+ */
+
#include <stdint.h>
#include <urcu-call-rcu.h>
-struct rcu_ht_node {
- struct rcu_ht_node *next;
- void *key;
- size_t key_len;
- unsigned long hash;
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * struct cds_lfht_node and struct _cds_lfht_node should be aligned on
+ * 8-bytes boundaries because the two lower bits are used as flags.
+ */
+
+struct _cds_lfht_node {
+ struct cds_lfht_node *next; /* ptr | DUMMY_FLAG | GC_FLAG | REMOVED_FLAG */
unsigned long reverse_hash;
- unsigned int dummy;
- void *value;
+} __attribute__((aligned(8)));
+
+struct cds_lfht_node {
+ /* cache-hot for iteration */
+ struct _cds_lfht_node p; /* needs to be first field */
+ void *key;
+ unsigned int key_len;
+ /* cache-cold for iteration */
struct rcu_head head;
};
-struct rcu_ht;
+struct cds_lfht;
/*
* Caution !
* Ensure reader and writer threads are registered as urcu readers.
*/
-typedef unsigned long (*ht_hash_fct)(void *key, size_t length,
- unsigned long seed);
-typedef unsigned long (*ht_compare_fct)(void *key1, size_t key1_len,
- void *key2, size_t key2_len);
+typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
+ unsigned long seed);
+typedef unsigned long (*cds_lfht_compare_fct)(void *key1, size_t key1_len,
+ void *key2, size_t key2_len);
+/*
+ * cds_lfht_node_init - initialize a hash table node
+ */
static inline
-void ht_node_init(struct rcu_ht_node *node, void *key,
- size_t key_len, void *value)
+void cds_lfht_node_init(struct cds_lfht_node *node, void *key,
+ size_t key_len)
{
node->key = key;
node->key_len = key_len;
- node->value = value;
- node->dummy = 0;
}
/*
- * init_size must be power of two.
+ * Hash table creation flags.
*/
-struct rcu_ht *ht_new(ht_hash_fct hash_fct,
- ht_compare_fct compare_fct,
- unsigned long hash_seed,
- unsigned long init_size,
- void (*ht_call_rcu)(struct rcu_head *head,
- void (*func)(struct rcu_head *head)));
+enum {
+ CDS_LFHT_AUTO_RESIZE = (1U << 0),
+};
-int ht_destroy(struct rcu_ht *ht);
+/*
+ * _cds_lfht_new - API used by cds_lfht_new wrapper. Do not use directly.
+ */
+struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
+ cds_lfht_compare_fct compare_fct,
+ unsigned long hash_seed,
+ unsigned long init_size,
+ int flags,
+ void (*cds_lfht_call_rcu)(struct rcu_head *head,
+ void (*func)(struct rcu_head *head)),
+ void (*cds_lfht_synchronize_rcu)(void),
+ void (*cds_lfht_rcu_read_lock)(void),
+ void (*cds_lfht_rcu_read_unlock)(void),
+ void (*cds_lfht_rcu_thread_offline)(void),
+ void (*cds_lfht_rcu_thread_online)(void),
+ void (*cds_lfht_rcu_register_thread)(void),
+ void (*cds_lfht_rcu_unregister_thread)(void),
+ pthread_attr_t *attr);
-/* Call with rcu_read_lock held. */
-struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len);
+/*
+ * cds_lfht_new - allocate a hash table.
+ * @hash_fct: the hashing function.
+ * @compare_fct: the key comparison function.
+ * @hash_seed: the seed for hash function.
+ * @init_size: number of nodes to allocate initially. Must be power of two.
+ * @flags: hash table creation flags (can be combined with bitwise or: '|').
+ * 0: no flags.
+ * CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
+ * @attr: optional resize worker thread attributes. NULL for default.
+ *
+ * Return NULL on error.
+ * Note: the RCU flavor must be already included before the hash table header.
+ *
+ * The programmer is responsible for ensuring that resize operation has a
+ * priority equal to hash table updater threads. It should be performed by
+ * specifying the appropriate priority in the pthread "attr" argument, and,
+ * for CDS_LFHT_AUTO_RESIZE, by ensuring that call_rcu worker threads also have
+ * this priority level. Having lower priority for call_rcu and resize threads
+ * does not pose any correctness issue, but the resize operations could be
+ * starved by updates, thus leading to long hash table bucket chains.
+ */
+static inline
+struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
+ cds_lfht_compare_fct compare_fct,
+ unsigned long hash_seed,
+ unsigned long init_size,
+ int flags,
+ pthread_attr_t *attr)
+{
+ return _cds_lfht_new(hash_fct, compare_fct, hash_seed,
+ init_size, flags,
+ call_rcu, synchronize_rcu, rcu_read_lock,
+ rcu_read_unlock, rcu_thread_offline,
+ rcu_thread_online, rcu_register_thread,
+ rcu_unregister_thread, attr);
+}
-/* Call with rcu_read_lock held. */
-void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node);
+/*
+ * cds_lfht_destroy - destroy a hash table.
+ * @ht: the hash table to destroy.
+ * @attr: (output) resize worker thread attributes, as received by cds_lfht_new.
+ * The caller will typically want to free this pointer if dynamically
+ * allocated.
+ *
+ * Return 0 on success, negative error value on error.
+ */
+int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
-/* Call with rcu_read_lock held. */
-int ht_add_unique(struct rcu_ht *ht, struct rcu_ht_node *node);
+/*
+ * cds_lfht_count_nodes - count the number of nodes in the hash table.
+ *
+ * Call with rcu_read_lock held.
+ */
+void cds_lfht_count_nodes(struct cds_lfht *ht,
+ unsigned long *count,
+ unsigned long *removed);
+
+/*
+ * cds_lfht_lookup - lookup a node by key.
+ *
+ * Return NULL if not found.
+ * Call with rcu_read_lock held.
+ */
+struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len);
+
+/*
+ * cds_lfht_next - get the next item with same key (after a lookup).
+ *
+ * Return NULL if no following node exists with same key.
+ * RCU read-side lock must be held across cds_lfht_lookup and cds_lfht_next calls, and also
+ * between cds_lfht_next calls using the node returned by a previous
+ * cds_lfht_next. Call with rcu_read_lock held.
+ */
+struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_node *node);
+
+/*
+ * cds_lfht_add - add a node to the hash table.
+ *
+ * Call with rcu_read_lock held.
+ * This function supports adding redundant keys into the table.
+ */
+void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
+
+/*
+ * cds_lfht_add_unique - add a node to hash table, if key is not present.
+ *
+ * Return the node added upon success.
+ * Return the unique node already present upon failure. If
+ * cds_lfht_add_unique fails, the node passed as parameter should be
+ * freed by the caller.
+ * Call with rcu_read_lock held.
+ *
+ * The semantic of this function is that if only this function is used
+ * to add keys into the table, no duplicated keys should ever be
+ * observable in the table. The same guarantee apply for combination of
+ * add_unique and replace (see below).
+ */
+struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, struct cds_lfht_node *node);
-/* Call with rcu_read_lock held. */
-int ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node);
+/*
+ * cds_lfht_replace - replace a node within hash table.
+ *
+ * Return the node replaced upon success. If no node matching the key
+ * was present, return NULL, which also means the operation succeeded.
+ * This replacement operation should never fail.
+ * Call with rcu_read_lock held.
+ * After successful replacement, a grace period must be waited for before
+ * freeing the memory reserved for the returned node.
+ *
+ * The semantic of replacement vs lookups is the following: if lookups
+ * are performed between a key insertion and its removal, we guarantee
+ * that the lookups will always find the key if it is replaced
+ * concurrently with the lookups. Providing this guarantee require us to
+ * pin the node to remove in place (disallowing any insertion after this
+ * node temporarily) before we can proceed to its exchange with the new
+ * node atomically. This renders the "replace" operation not strictly
+ * lock-free, because a thread crashing in the middle of the replace
+ * operation could stop progress for other updaters.
+ *
+ * Providing this semantic allows us to ensure that replacement-only
+ * schemes will never generate duplicated keys. It also allows us to
+ * guarantee that a combination of replacement and add_unique updates
+ * will never generate duplicated keys.
+ */
+struct cds_lfht_node *cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_node *node);
-void ht_resize(struct rcu_ht *ht, int growth);
+/*
+ * cds_lfht_del - remove node from hash table.
+ *
+ * Return 0 if the node is successfully removed.
+ * Node can be looked up with cds_lfht_lookup. RCU read-side lock must
+ * be held between lookup and removal.
+ * Call with rcu_read_lock held.
+ * After successful removal, a grace period must be waited for before
+ * freeing the memory reserved for node.
+ */
+int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node);
+
+/*
+ * cds_lfht_resize - Force a hash table resize
+ * @new_size: update to this hash table size.
+ */
+void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
+
+#ifdef __cplusplus
+}
+#endif
#endif /* _URCU_RCULFHASH_H */
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