liblttng-ust/rculfhash.h

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