* 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>
/*
* struct cds_lfht_node and struct _cds_lfht_node should be aligned on
- * 4-bytes boundaries because the two lower bits are used as flags.
+ * 8-bytes boundaries because the two lower bits are used as flags.
*/
struct _cds_lfht_node {
- struct cds_lfht_node *next; /* ptr | DUMMY_FLAG | REMOVED_FLAG */
+ struct cds_lfht_node *next; /* ptr | DUMMY_FLAG | GC_FLAG | REMOVED_FLAG */
unsigned long reverse_hash;
-};
+} __attribute__((aligned(8)));
struct cds_lfht_node {
/* cache-hot for iteration */
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_thread_online)(void),
+ void (*cds_lfht_rcu_register_thread)(void),
+ void (*cds_lfht_rcu_unregister_thread)(void),
+ pthread_attr_t *attr);
/*
* 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.
*
- * init_size must be power of two.
* 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)
+ 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_thread_online, rcu_register_thread,
+ rcu_unregister_thread, attr);
}
/*
* 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);
+int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
/*
* cds_lfht_count_nodes - count the number of nodes in the hash table.
*
* 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.
+ * 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.
+ * 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);
/*
- * cds_lfht_remove - remove node from hash table.
+ * 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);
+
+/*
+ * cds_lfht_del - remove node from hash table.
*
- * Node can be looked up with cds_lfht_lookup. RCU read-side lock must be held between
- * lookup and removal.
+ * 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_remove(struct cds_lfht *ht, struct cds_lfht_node *node);
+int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node);
/*
* cds_lfht_resize - Force a hash table resize
projects / urcu.git / blobdiff