X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu%2Frculfhash.h;h=008b1d49f55ae86ae4bcdf86c2ce2a8c0a1c7617;hp=bc9f232d65deb6632f9c19a84dceb2a6e901a377;hb=7f52427be704778d53f85e17fb71629b50ada827;hpb=f22dd01d7941170a1b1b0275344a6e6cd83dbcc6 diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h index bc9f232..008b1d4 100644 --- a/urcu/rculfhash.h +++ b/urcu/rculfhash.h @@ -37,11 +37,26 @@ extern "C" { * 4-bytes boundaries because the two lower bits are used as flags. */ +/* + * _cds_lfht_node: Contains the internal pointers and reverse-hash + * value required for lookup and traversal of the hash table. + */ struct _cds_lfht_node { struct cds_lfht_node *next; /* ptr | DUMMY_FLAG | REMOVED_FLAG */ unsigned long reverse_hash; -}; +} __attribute__((aligned(4))); +/* + * cds_lfht_node: Contains the full key and length required to check for + * an actual match, and also contains an rcu_head structure that is used + * by RCU to track a node through a given RCU grace period. There is an + * instance of _cds_lfht_node enclosed as a field within each + * _cds_lfht_node structure. + * + * struct cds_lfht_node can be embedded into a structure (as a field). + * caa_container_of() can be used to get the structure from the struct + * cds_lfht_node after a lookup. + */ struct cds_lfht_node { /* cache-hot for iteration */ struct _cds_lfht_node p; /* needs to be first field */ @@ -51,6 +66,17 @@ struct cds_lfht_node { struct rcu_head head; }; +/* cds_lfht_iter: Used to track state while traversing a hash chain. */ +struct cds_lfht_iter { + struct cds_lfht_node *node, *next; +}; + +static inline +struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter) +{ + return iter->node; +} + struct cds_lfht; /* @@ -79,6 +105,7 @@ void cds_lfht_node_init(struct cds_lfht_node *node, void *key, */ enum { CDS_LFHT_AUTO_RESIZE = (1U << 0), + CDS_LFHT_ACCOUNTING = (1U << 1), }; /* @@ -88,6 +115,7 @@ 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, + unsigned long min_alloc_size, int flags, void (*cds_lfht_call_rcu)(struct rcu_head *head, void (*func)(struct rcu_head *head)), @@ -95,7 +123,10 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct, 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. @@ -103,65 +134,119 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct, * @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. + * @min_alloc_size: the smallest allocation size to use. 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. + * Threads calling this API need to be registered RCU read-side threads. */ 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) + unsigned long min_alloc_size, + int flags, + pthread_attr_t *attr) { return _cds_lfht_new(hash_fct, compare_fct, hash_seed, - init_size, flags, + init_size, min_alloc_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. The attr point can be NULL if the caller does not + * need to be informed of the value passed to cds_lfht_new(). * * Return 0 on success, negative error value on error. + * Threads calling this API need to be registered RCU read-side threads. */ -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. - * + * @ht: the hash table. + * @split_count_before: Sample the node count split-counter before traversal. + * @count: Traverse the hash table, count the number of nodes observed. + * @removed: Number of logically removed nodes observed during traversal. + * @split_count_after: Sample the node count split-counter after traversal. * Call with rcu_read_lock held. + * Threads calling this API need to be registered RCU read-side threads. */ void cds_lfht_count_nodes(struct cds_lfht *ht, - unsigned long *count, - unsigned long *removed); + long *split_count_before, + unsigned long *count, + unsigned long *removed, + long *split_count_after); /* * cds_lfht_lookup - lookup a node by key. * - * Return NULL if not found. + * Output in "*iter". *iter->node set to NULL if not found. + * Call with rcu_read_lock held. + * Threads calling this API need to be registered RCU read-side threads. + */ +void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len, + struct cds_lfht_iter *iter); + +/* + * cds_lfht_next_duplicate - get the next item with same key (after a lookup). + * + * Uses an iterator initialized by a lookup. + * Sets *iter-node to the following node with same key. + * Sets *iter->node to 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. + * Threads calling this API need to be registered RCU read-side threads. */ -struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len); +void cds_lfht_next_duplicate(struct cds_lfht *ht, struct cds_lfht_iter *iter); /* - * cds_lfht_next - get the next item with same key (after a lookup). + * cds_lfht_first - get the first node in the 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. + * Output in "*iter". *iter->node set to NULL if table is empty. * Call with rcu_read_lock held. + * Threads calling this API need to be registered RCU read-side threads. */ -struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_node *node); +void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter); + +/* + * cds_lfht_next - get the next node in the table. + * + * Input/Output in "*iter". *iter->node set to NULL if *iter was + * pointing to the last table node. + * Call with rcu_read_lock held. + * Threads calling this API need to be registered RCU read-side threads. + */ +void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter); /* * cds_lfht_add - add a node to the hash table. * + * This function supports adding redundant keys into the table. * Call with rcu_read_lock held. + * Threads calling this API need to be registered RCU read-side threads. */ void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node); @@ -169,24 +254,94 @@ 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. + * Threads calling this API need to be registered RCU read-side threads. + * + * 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 add_replace (see below). + */ +struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, + struct cds_lfht_node *node); + +/* + * cds_lfht_add_replace - replace or add 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. + * Threads calling this API need to be registered RCU read-side threads. + * 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 unique insertion and its removal, we + * guarantee that the lookups and get next will always find exactly one + * instance of the key if it is replaced concurrently with the lookups. + * + * 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 add_replace and add_unique updates + * will never generate duplicated keys. + */ +struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht, + struct cds_lfht_node *node); + +/* + * cds_lfht_replace - replace a node pointer to by iter within hash table. + * + * Return 0 if replacement is successful, negative value otherwise. + * Replacing a NULL old node or an already removed node will fail with a + * negative value. + * Old node can be looked up with cds_lfht_lookup and cds_lfht_next. + * RCU read-side lock must be held between lookup and replacement. + * Call with rcu_read_lock held. + * Threads calling this API need to be registered RCU read-side threads. + * After successful replacement, a grace period must be waited for before + * freeing the memory reserved for the old node (which can be accessed + * with cds_lfht_iter_get_node). + * + * The semantic of replacement vs lookups is the following: if lookups + * are performed between a key unique insertion and its removal, we + * guarantee that the lookups and get next will always find exactly one + * instance of the key if it is replaced concurrently with the lookups. + * + * 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 add_replace and add_unique updates + * will never generate duplicated keys. */ -struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, struct cds_lfht_node *node); +int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter, + struct cds_lfht_node *new_node); /* - * cds_lfht_remove - remove node from hash table. + * cds_lfht_del - remove node pointed to by iterator 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, negative value + * otherwise. + * Replacing a NULL node or an already removed node will fail with a + * negative value. + * Node can be looked up with cds_lfht_lookup and cds_lfht_next. + * cds_lfht_iter_get_node. + * RCU read-side lock must be held between lookup and removal. * Call with rcu_read_lock held. + * Threads calling this API need to be registered RCU read-side threads. + * After successful removal, a grace period must be waited for before + * freeing the memory reserved for old node (which can be accessed with + * cds_lfht_iter_get_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_iter *iter); /* * cds_lfht_resize - Force a hash table resize * @new_size: update to this hash table size. + * + * Threads calling this API need to be registered RCU read-side threads. */ void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);