liblttng-ust/rculfhash.h

   1 #ifndef _LTTNG_UST_RCULFHASH_H
   2 #define _LTTNG_UST_RCULFHASH_H
   3
   4 /*
   5  * urcu/rculfhash.h
   6  *
   7  * Userspace RCU library - Lock-Free RCU Hash Table
   8  *
   9  * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
  11  *
  12  * This library is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU Lesser General Public
  14  * License as published by the Free Software Foundation; either
  15  * version 2.1 of the License, or (at your option) any later version.
  16  *
  17  * This library is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * Lesser General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public
  23  * License along with this library; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  25  */
  26
  27 #include <stdint.h>
  28 #include <pthread.h>
  29 #include <urcu/compiler.h>
  30
  31 #ifdef __cplusplus
  32 extern "C" {
  33 #endif
  34
  35 struct lttng_ust_lfht;
  36
  37 /*
  38  * lttng_ust_lfht_node: Contains the next pointers and reverse-hash
  39  * value required for lookup and traversal of the hash table.
  40  *
  41  * struct lttng_ust_lfht_node should be aligned on 8-bytes boundaries because
  42  * the three lower bits are used as flags. It is worth noting that the
  43  * information contained within these three bits could be represented on
  44  * two bits by re-using the same bit for REMOVAL_OWNER_FLAG and
  45  * BUCKET_FLAG. This can be done if we ensure that no iterator nor
  46  * updater check the BUCKET_FLAG after it detects that the REMOVED_FLAG
  47  * is set. Given the minimum size of struct lttng_ust_lfht_node is 8 bytes on
  48  * 32-bit architectures, we choose to go for simplicity and reserve
  49  * three bits.
  50  *
  51  * struct lttng_ust_lfht_node can be embedded into a structure (as a field).
  52  * caa_container_of() can be used to get the structure from the struct
  53  * lttng_ust_lfht_node after a lookup.
  54  *
  55  * The structure which embeds it typically holds the key (or key-value
  56  * pair) of the object. The caller code is responsible for calculation
  57  * of the hash value for lttng_ust_lfht APIs.
  58  */
  59 struct lttng_ust_lfht_node {
  60         struct lttng_ust_lfht_node *next;       /* ptr | REMOVAL_OWNER_FLAG | BUCKET_FLAG | REMOVED_FLAG */
  61         unsigned long reverse_hash;
  62 } __attribute__((aligned(8)));
  63
  64 /* lttng_ust_lfht_iter: Used to track state while traversing a hash chain. */
  65 struct lttng_ust_lfht_iter {
  66         struct lttng_ust_lfht_node *node, *next;
  67 };
  68
  69 static inline
  70 struct lttng_ust_lfht_node *lttng_ust_lfht_iter_get_node(struct lttng_ust_lfht_iter *iter)
  71 {
  72         return iter->node;
  73 }
  74
  75 struct rcu_flavor_struct;
  76
  77 /*
  78  * Caution !
  79  * Ensure reader and writer threads are registered as urcu readers.
  80  */
  81
  82 typedef int (*lttng_ust_lfht_match_fct)(struct lttng_ust_lfht_node *node, const void *key);
  83
  84 /*
  85  * lttng_ust_lfht_node_init - initialize a hash table node
  86  * @node: the node to initialize.
  87  *
  88  * This function is kept to be eventually used for debugging purposes
  89  * (detection of memory corruption).
  90  */
  91 static inline
  92 void lttng_ust_lfht_node_init(struct lttng_ust_lfht_node *node)
  93 {
  94 }
  95
  96 /*
  97  * Hash table creation flags.
  98  */
  99 enum {
 100         LTTNG_UST_LFHT_AUTO_RESIZE = (1U << 0),
 101         LTTNG_UST_LFHT_ACCOUNTING = (1U << 1),
 102 };
 103
 104 struct lttng_ust_lfht_mm_type {
 105         struct lttng_ust_lfht *(*alloc_lttng_ust_lfht)(unsigned long min_nr_alloc_buckets,
 106                         unsigned long max_nr_buckets);
 107         void (*alloc_bucket_table)(struct lttng_ust_lfht *ht, unsigned long order);
 108         void (*free_bucket_table)(struct lttng_ust_lfht *ht, unsigned long order);
 109         struct lttng_ust_lfht_node *(*bucket_at)(struct lttng_ust_lfht *ht,
 110                         unsigned long index);
 111 };
 112
 113 extern const struct lttng_ust_lfht_mm_type lttng_ust_lfht_mm_order;
 114 extern const struct lttng_ust_lfht_mm_type lttng_ust_lfht_mm_chunk;
 115 extern const struct lttng_ust_lfht_mm_type lttng_ust_lfht_mm_mmap;
 116
 117 /*
 118  * lttng_ust_lfht_new - allocate a hash table.
 119  * @init_size: number of buckets to allocate initially. Must be power of two.
 120  * @min_nr_alloc_buckets: the minimum number of allocated buckets.
 121  *                        (must be power of two)
 122  * @max_nr_buckets: the maximum number of hash table buckets allowed.
 123  *                  (must be power of two, 0 is accepted, means
 124  *                  "infinite")
 125  * @flags: hash table creation flags (can be combined with bitwise or: '|').
 126  *           0: no flags.
 127  *           LTTNG_UST_LFHT_AUTO_RESIZE: automatically resize hash table.
 128  *           LTTNG_UST_LFHT_ACCOUNTING: count the number of node addition
 129  *                                and removal in the table
 130  *
 131  * Return NULL on error.
 132  * Note: the RCU flavor must be already included before the hash table header.
 133  */
 134 extern
 135 struct lttng_ust_lfht *lttng_ust_lfht_new(unsigned long init_size,
 136                         unsigned long min_nr_alloc_buckets,
 137                         unsigned long max_nr_buckets,
 138                         int flags,
 139                         const struct lttng_ust_lfht_mm_type *mm);
 140
 141 /*
 142  * lttng_ust_lfht_destroy - destroy a hash table.
 143  * @ht: the hash table to destroy.
 144  *
 145  * Return 0 on success, negative error value on error.
 146
 147  * Prior to liburcu 0.10:
 148  * - Threads calling this API need to be registered RCU read-side
 149  *   threads.
 150  * - lttng_ust_lfht_destroy should *not* be called from a RCU read-side
 151  *   critical section. It should *not* be called from a call_rcu thread
 152  *   context neither.
 153  *
 154  * Starting from liburcu 0.10, rculfhash implements its own worker
 155  * thread to handle resize operations, which removes RCU requirements on
 156  * lttng_ust_lfht_destroy.
 157  */
 158 extern
 159 int lttng_ust_lfht_destroy(struct lttng_ust_lfht *ht);
 160
 161 /*
 162  * lttng_ust_lfht_count_nodes - count the number of nodes in the hash table.
 163  * @ht: the hash table.
 164  * @split_count_before: sample the node count split-counter before traversal.
 165  * @count: traverse the hash table, count the number of nodes observed.
 166  * @split_count_after: sample the node count split-counter after traversal.
 167  *
 168  * Call with rcu_read_lock held.
 169  * Threads calling this API need to be registered RCU read-side threads.
 170  */
 171 extern
 172 void lttng_ust_lfht_count_nodes(struct lttng_ust_lfht *ht,
 173                 long *split_count_before,
 174                 unsigned long *count,
 175                 long *split_count_after);
 176
 177 /*
 178  * lttng_ust_lfht_lookup - lookup a node by key.
 179  * @ht: the hash table.
 180  * @hash: the key hash.
 181  * @match: the key match function.
 182  * @key: the current node key.
 183  * @iter: node, if found (output). *iter->node set to NULL if not found.
 184  *
 185  * Call with rcu_read_lock held.
 186  * Threads calling this API need to be registered RCU read-side threads.
 187  * This function acts as a rcu_dereference() to read the node pointer.
 188  */
 189 extern
 190 void lttng_ust_lfht_lookup(struct lttng_ust_lfht *ht, unsigned long hash,
 191                 lttng_ust_lfht_match_fct match, const void *key,
 192                 struct lttng_ust_lfht_iter *iter);
 193
 194 /*
 195  * lttng_ust_lfht_next_duplicate - get the next item with same key, after iterator.
 196  * @ht: the hash table.
 197  * @match: the key match function.
 198  * @key: the current node key.
 199  * @iter: input: current iterator.
 200  *        output: node, if found. *iter->node set to NULL if not found.
 201  *
 202  * Uses an iterator initialized by a lookup or traversal. Important: the
 203  * iterator _needs_ to be initialized before calling
 204  * lttng_ust_lfht_next_duplicate.
 205  * Sets *iter-node to the following node with same key.
 206  * Sets *iter->node to NULL if no following node exists with same key.
 207  * RCU read-side lock must be held across lttng_ust_lfht_lookup and
 208  * lttng_ust_lfht_next calls, and also between lttng_ust_lfht_next calls using the
 209  * node returned by a previous lttng_ust_lfht_next.
 210  * Call with rcu_read_lock held.
 211  * Threads calling this API need to be registered RCU read-side threads.
 212  * This function acts as a rcu_dereference() to read the node pointer.
 213  */
 214 extern
 215 void lttng_ust_lfht_next_duplicate(struct lttng_ust_lfht *ht,
 216                 lttng_ust_lfht_match_fct match, const void *key,
 217                 struct lttng_ust_lfht_iter *iter);
 218
 219 /*
 220  * lttng_ust_lfht_first - get the first node in the table.
 221  * @ht: the hash table.
 222  * @iter: First node, if exists (output). *iter->node set to NULL if not found.
 223  *
 224  * Output in "*iter". *iter->node set to NULL if table is empty.
 225  * Call with rcu_read_lock held.
 226  * Threads calling this API need to be registered RCU read-side threads.
 227  * This function acts as a rcu_dereference() to read the node pointer.
 228  */
 229 extern
 230 void lttng_ust_lfht_first(struct lttng_ust_lfht *ht, struct lttng_ust_lfht_iter *iter);
 231
 232 /*
 233  * lttng_ust_lfht_next - get the next node in the table.
 234  * @ht: the hash table.
 235  * @iter: input: current iterator.
 236  *        output: next node, if exists. *iter->node set to NULL if not found.
 237  *
 238  * Input/Output in "*iter". *iter->node set to NULL if *iter was
 239  * pointing to the last table node.
 240  * Call with rcu_read_lock held.
 241  * Threads calling this API need to be registered RCU read-side threads.
 242  * This function acts as a rcu_dereference() to read the node pointer.
 243  */
 244 extern
 245 void lttng_ust_lfht_next(struct lttng_ust_lfht *ht, struct lttng_ust_lfht_iter *iter);
 246
 247 /*
 248  * lttng_ust_lfht_add - add a node to the hash table.
 249  * @ht: the hash table.
 250  * @hash: the key hash.
 251  * @node: the node to add.
 252  *
 253  * This function supports adding redundant keys into the table.
 254  * Call with rcu_read_lock held.
 255  * Threads calling this API need to be registered RCU read-side threads.
 256  * This function issues a full memory barrier before and after its
 257  * atomic commit.
 258  */
 259 extern
 260 void lttng_ust_lfht_add(struct lttng_ust_lfht *ht, unsigned long hash,
 261                 struct lttng_ust_lfht_node *node);
 262
 263 /*
 264  * lttng_ust_lfht_add_unique - add a node to hash table, if key is not present.
 265  * @ht: the hash table.
 266  * @hash: the node's hash.
 267  * @match: the key match function.
 268  * @key: the node's key.
 269  * @node: the node to try adding.
 270  *
 271  * Return the node added upon success.
 272  * Return the unique node already present upon failure. If
 273  * lttng_ust_lfht_add_unique fails, the node passed as parameter should be
 274  * freed by the caller. In this case, the caller does NOT need to wait
 275  * for a grace period before freeing or re-using the node.
 276  * Call with rcu_read_lock held.
 277  * Threads calling this API need to be registered RCU read-side threads.
 278  *
 279  * The semantic of this function is that if only this function is used
 280  * to add keys into the table, no duplicated keys should ever be
 281  * observable in the table. The same guarantee apply for combination of
 282  * add_unique and add_replace (see below).
 283  *
 284  * Upon success, this function issues a full memory barrier before and
 285  * after its atomic commit. Upon failure, this function acts like a
 286  * simple lookup operation: it acts as a rcu_dereference() to read the
 287  * node pointer. The failure case does not guarantee any other memory
 288  * barrier.
 289  */
 290 extern
 291 struct lttng_ust_lfht_node *lttng_ust_lfht_add_unique(struct lttng_ust_lfht *ht,
 292                 unsigned long hash,
 293                 lttng_ust_lfht_match_fct match,
 294                 const void *key,
 295                 struct lttng_ust_lfht_node *node);
 296
 297 /*
 298  * lttng_ust_lfht_add_replace - replace or add a node within hash table.
 299  * @ht: the hash table.
 300  * @hash: the node's hash.
 301  * @match: the key match function.
 302  * @key: the node's key.
 303  * @node: the node to add.
 304  *
 305  * Return the node replaced upon success. If no node matching the key
 306  * was present, return NULL, which also means the operation succeeded.
 307  * This replacement operation should never fail.
 308  * Call with rcu_read_lock held.
 309  * Threads calling this API need to be registered RCU read-side threads.
 310  * After successful replacement, a grace period must be waited for before
 311  * freeing or re-using the memory reserved for the returned node.
 312  *
 313  * The semantic of replacement vs lookups and traversals is the
 314  * following: if lookups and traversals are performed between a key
 315  * unique insertion and its removal, we guarantee that the lookups and
 316  * traversals will always find exactly one instance of the key if it is
 317  * replaced concurrently with the lookups.
 318  *
 319  * Providing this semantic allows us to ensure that replacement-only
 320  * schemes will never generate duplicated keys. It also allows us to
 321  * guarantee that a combination of add_replace and add_unique updates
 322  * will never generate duplicated keys.
 323  *
 324  * This function issues a full memory barrier before and after its
 325  * atomic commit.
 326  */
 327 extern
 328 struct lttng_ust_lfht_node *lttng_ust_lfht_add_replace(struct lttng_ust_lfht *ht,
 329                 unsigned long hash,
 330                 lttng_ust_lfht_match_fct match,
 331                 const void *key,
 332                 struct lttng_ust_lfht_node *node);
 333
 334 /*
 335  * lttng_ust_lfht_replace - replace a node pointed to by iter within hash table.
 336  * @ht: the hash table.
 337  * @old_iter: the iterator position of the node to replace.
 338  * @hash: the node's hash.
 339  * @match: the key match function.
 340  * @key: the node's key.
 341  * @new_node: the new node to use as replacement.
 342  *
 343  * Return 0 if replacement is successful, negative value otherwise.
 344  * Replacing a NULL old node or an already removed node will fail with
 345  * -ENOENT.
 346  * If the hash or value of the node to replace and the new node differ,
 347  * this function returns -EINVAL without proceeding to the replacement.
 348  * Old node can be looked up with lttng_ust_lfht_lookup and lttng_ust_lfht_next.
 349  * RCU read-side lock must be held between lookup and replacement.
 350  * Call with rcu_read_lock held.
 351  * Threads calling this API need to be registered RCU read-side threads.
 352  * After successful replacement, a grace period must be waited for before
 353  * freeing or re-using the memory reserved for the old node (which can
 354  * be accessed with lttng_ust_lfht_iter_get_node).
 355  *
 356  * The semantic of replacement vs lookups is the same as
 357  * lttng_ust_lfht_add_replace().
 358  *
 359  * Upon success, this function issues a full memory barrier before and
 360  * after its atomic commit. Upon failure, this function does not issue
 361  * any memory barrier.
 362  */
 363 extern
 364 int lttng_ust_lfht_replace(struct lttng_ust_lfht *ht,
 365                 struct lttng_ust_lfht_iter *old_iter,
 366                 unsigned long hash,
 367                 lttng_ust_lfht_match_fct match,
 368                 const void *key,
 369                 struct lttng_ust_lfht_node *new_node);
 370
 371 /*
 372  * lttng_ust_lfht_del - remove node pointed to by iterator from hash table.
 373  * @ht: the hash table.
 374  * @node: the node to delete.
 375  *
 376  * Return 0 if the node is successfully removed, negative value
 377  * otherwise.
 378  * Deleting a NULL node or an already removed node will fail with a
 379  * negative value.
 380  * Node can be looked up with lttng_ust_lfht_lookup and lttng_ust_lfht_next,
 381  * followed by use of lttng_ust_lfht_iter_get_node.
 382  * RCU read-side lock must be held between lookup and removal.
 383  * Call with rcu_read_lock held.
 384  * Threads calling this API need to be registered RCU read-side threads.
 385  * After successful removal, a grace period must be waited for before
 386  * freeing or re-using the memory reserved for old node (which can be
 387  * accessed with lttng_ust_lfht_iter_get_node).
 388  * Upon success, this function issues a full memory barrier before and
 389  * after its atomic commit. Upon failure, this function does not issue
 390  * any memory barrier.
 391  */
 392 extern
 393 int lttng_ust_lfht_del(struct lttng_ust_lfht *ht, struct lttng_ust_lfht_node *node);
 394
 395 /*
 396  * lttng_ust_lfht_is_node_deleted - query whether a node is removed from hash table.
 397  *
 398  * Return non-zero if the node is deleted from the hash table, 0
 399  * otherwise.
 400  * Node can be looked up with lttng_ust_lfht_lookup and lttng_ust_lfht_next,
 401  * followed by use of lttng_ust_lfht_iter_get_node.
 402  * RCU read-side lock must be held between lookup and call to this
 403  * function.
 404  * Call with rcu_read_lock held.
 405  * Threads calling this API need to be registered RCU read-side threads.
 406  * This function does not issue any memory barrier.
 407  */
 408 extern
 409 int lttng_ust_lfht_is_node_deleted(const struct lttng_ust_lfht_node *node);
 410
 411 /*
 412  * lttng_ust_lfht_resize - Force a hash table resize
 413  * @ht: the hash table.
 414  * @new_size: update to this hash table size.
 415  *
 416  * Threads calling this API need to be registered RCU read-side threads.
 417  * This function does not (necessarily) issue memory barriers.
 418  * lttng_ust_lfht_resize should *not* be called from a RCU read-side critical
 419  * section.
 420  */
 421 extern
 422 void lttng_ust_lfht_resize(struct lttng_ust_lfht *ht, unsigned long new_size);
 423
 424 /*
 425  * Note: it is safe to perform element removal (del), replacement, or
 426  * any hash table update operation during any of the following hash
 427  * table traversals.
 428  * These functions act as rcu_dereference() to read the node pointers.
 429  */
 430 #define lttng_ust_lfht_for_each(ht, iter, node)                         \
 431         for (lttng_ust_lfht_first(ht, iter),                                    \
 432                         node = lttng_ust_lfht_iter_get_node(iter);              \
 433                 node != NULL;                                           \
 434                 lttng_ust_lfht_next(ht, iter),                          \
 435                         node = lttng_ust_lfht_iter_get_node(iter))
 436
 437 #define lttng_ust_lfht_for_each_duplicate(ht, hash, match, key, iter, node)     \
 438         for (lttng_ust_lfht_lookup(ht, hash, match, key, iter),         \
 439                         node = lttng_ust_lfht_iter_get_node(iter);              \
 440                 node != NULL;                                           \
 441                 lttng_ust_lfht_next_duplicate(ht, match, key, iter),            \
 442                         node = lttng_ust_lfht_iter_get_node(iter))
 443
 444 #define lttng_ust_lfht_for_each_entry(ht, iter, pos, member)                    \
 445         for (lttng_ust_lfht_first(ht, iter),                                    \
 446                         pos = caa_container_of(lttng_ust_lfht_iter_get_node(iter), \
 447                                         __typeof__(*(pos)), member);    \
 448                 lttng_ust_lfht_iter_get_node(iter) != NULL;                     \
 449                 lttng_ust_lfht_next(ht, iter),                          \
 450                         pos = caa_container_of(lttng_ust_lfht_iter_get_node(iter), \
 451                                         __typeof__(*(pos)), member))
 452
 453 #define lttng_ust_lfht_for_each_entry_duplicate(ht, hash, match, key,           \
 454                                 iter, pos, member)                      \
 455         for (lttng_ust_lfht_lookup(ht, hash, match, key, iter),         \
 456                         pos = caa_container_of(lttng_ust_lfht_iter_get_node(iter), \
 457                                         __typeof__(*(pos)), member);    \
 458                 lttng_ust_lfht_iter_get_node(iter) != NULL;                     \
 459                 lttng_ust_lfht_next_duplicate(ht, match, key, iter),            \
 460                         pos = caa_container_of(lttng_ust_lfht_iter_get_node(iter), \
 461                                         __typeof__(*(pos)), member))
 462
 463 #ifdef __cplusplus
 464 }
 465 #endif
 466
 467 #endif /* _LTTNG_UST_RCULFHASH_H */