Add `urcu_posix_assert()` as `assert()` replacement
[urcu.git] / src / rculfhash.c
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5e28c532 1/*
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2 * rculfhash.c
3 *
1475579c 4 * Userspace RCU library - Lock-Free Resizable RCU Hash Table
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5 *
6 * Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
0dcf4847 7 * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
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8 *
9 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * This library is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this library; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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22 */
23
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24/*
25 * Based on the following articles:
26 * - Ori Shalev and Nir Shavit. Split-ordered lists: Lock-free
27 * extensible hash tables. J. ACM 53, 3 (May 2006), 379-405.
28 * - Michael, M. M. High performance dynamic lock-free hash tables
29 * and list-based sets. In Proceedings of the fourteenth annual ACM
30 * symposium on Parallel algorithms and architectures, ACM Press,
31 * (2002), 73-82.
32 *
1475579c 33 * Some specificities of this Lock-Free Resizable RCU Hash Table
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34 * implementation:
35 *
36 * - RCU read-side critical section allows readers to perform hash
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37 * table lookups, as well as traversals, and use the returned objects
38 * safely by allowing memory reclaim to take place only after a grace
39 * period.
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40 * - Add and remove operations are lock-free, and do not need to
41 * allocate memory. They need to be executed within RCU read-side
42 * critical section to ensure the objects they read are valid and to
43 * deal with the cmpxchg ABA problem.
44 * - add and add_unique operations are supported. add_unique checks if
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45 * the node key already exists in the hash table. It ensures not to
46 * populate a duplicate key if the node key already exists in the hash
47 * table.
48 * - The resize operation executes concurrently with
49 * add/add_unique/add_replace/remove/lookup/traversal.
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50 * - Hash table nodes are contained within a split-ordered list. This
51 * list is ordered by incrementing reversed-bits-hash value.
1ee8f000 52 * - An index of bucket nodes is kept. These bucket nodes are the hash
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53 * table "buckets". These buckets are internal nodes that allow to
54 * perform a fast hash lookup, similarly to a skip list. These
55 * buckets are chained together in the split-ordered list, which
56 * allows recursive expansion by inserting new buckets between the
57 * existing buckets. The split-ordered list allows adding new buckets
58 * between existing buckets as the table needs to grow.
59 * - The resize operation for small tables only allows expanding the
60 * hash table. It is triggered automatically by detecting long chains
61 * in the add operation.
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62 * - The resize operation for larger tables (and available through an
63 * API) allows both expanding and shrinking the hash table.
4c42f1b8 64 * - Split-counters are used to keep track of the number of
1475579c 65 * nodes within the hash table for automatic resize triggering.
e753ff5a 66 * - Resize operation initiated by long chain detection is executed by a
d0ec0ed2 67 * worker thread, which keeps lock-freedom of add and remove.
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68 * - Resize operations are protected by a mutex.
69 * - The removal operation is split in two parts: first, a "removed"
70 * flag is set in the next pointer within the node to remove. Then,
71 * a "garbage collection" is performed in the bucket containing the
72 * removed node (from the start of the bucket up to the removed node).
73 * All encountered nodes with "removed" flag set in their next
74 * pointers are removed from the linked-list. If the cmpxchg used for
75 * removal fails (due to concurrent garbage-collection or concurrent
76 * add), we retry from the beginning of the bucket. This ensures that
77 * the node with "removed" flag set is removed from the hash table
78 * (not visible to lookups anymore) before the RCU read-side critical
79 * section held across removal ends. Furthermore, this ensures that
80 * the node with "removed" flag set is removed from the linked-list
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81 * before its memory is reclaimed. After setting the "removal" flag,
82 * only the thread which removal is the first to set the "removal
83 * owner" flag (with an xchg) into a node's next pointer is considered
84 * to have succeeded its removal (and thus owns the node to reclaim).
85 * Because we garbage-collect starting from an invariant node (the
86 * start-of-bucket bucket node) up to the "removed" node (or find a
87 * reverse-hash that is higher), we are sure that a successful
88 * traversal of the chain leads to a chain that is present in the
1f67ba50 89 * linked-list (the start node is never removed) and that it does not
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90 * contain the "removed" node anymore, even if concurrent delete/add
91 * operations are changing the structure of the list concurrently.
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92 * - The add operations perform garbage collection of buckets if they
93 * encounter nodes with removed flag set in the bucket where they want
94 * to add their new node. This ensures lock-freedom of add operation by
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95 * helping the remover unlink nodes from the list rather than to wait
96 * for it do to so.
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97 * - There are three memory backends for the hash table buckets: the
98 * "order table", the "chunks", and the "mmap".
99 * - These bucket containers contain a compact version of the hash table
100 * nodes.
101 * - The RCU "order table":
102 * - has a first level table indexed by log2(hash index) which is
103 * copied and expanded by the resize operation. This order table
104 * allows finding the "bucket node" tables.
105 * - There is one bucket node table per hash index order. The size of
106 * each bucket node table is half the number of hashes contained in
107 * this order (except for order 0).
108 * - The RCU "chunks" is best suited for close interaction with a page
109 * allocator. It uses a linear array as index to "chunks" containing
110 * each the same number of buckets.
111 * - The RCU "mmap" memory backend uses a single memory map to hold
112 * all buckets.
5f177b1c 113 * - synchronize_rcu is used to garbage-collect the old bucket node table.
93d46c39 114 *
7f949215 115 * Ordering Guarantees:
0f5543cb 116 *
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117 * To discuss these guarantees, we first define "read" operation as any
118 * of the the basic cds_lfht_lookup, cds_lfht_next_duplicate,
119 * cds_lfht_first, cds_lfht_next operation, as well as
67ecffc0 120 * cds_lfht_add_unique (failure).
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121 *
122 * We define "read traversal" operation as any of the following
123 * group of operations
0f5543cb 124 * - cds_lfht_lookup followed by iteration with cds_lfht_next_duplicate
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125 * (and/or cds_lfht_next, although less common).
126 * - cds_lfht_add_unique (failure) followed by iteration with
127 * cds_lfht_next_duplicate (and/or cds_lfht_next, although less
128 * common).
129 * - cds_lfht_first followed iteration with cds_lfht_next (and/or
130 * cds_lfht_next_duplicate, although less common).
0f5543cb 131 *
bf09adc7 132 * We define "write" operations as any of cds_lfht_add, cds_lfht_replace,
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133 * cds_lfht_add_unique (success), cds_lfht_add_replace, cds_lfht_del.
134 *
135 * When cds_lfht_add_unique succeeds (returns the node passed as
136 * parameter), it acts as a "write" operation. When cds_lfht_add_unique
137 * fails (returns a node different from the one passed as parameter), it
138 * acts as a "read" operation. A cds_lfht_add_unique failure is a
139 * cds_lfht_lookup "read" operation, therefore, any ordering guarantee
140 * referring to "lookup" imply any of "lookup" or cds_lfht_add_unique
141 * (failure).
142 *
143 * We define "prior" and "later" node as nodes observable by reads and
144 * read traversals respectively before and after a write or sequence of
145 * write operations.
146 *
147 * Hash-table operations are often cascaded, for example, the pointer
148 * returned by a cds_lfht_lookup() might be passed to a cds_lfht_next(),
149 * whose return value might in turn be passed to another hash-table
150 * operation. This entire cascaded series of operations must be enclosed
151 * by a pair of matching rcu_read_lock() and rcu_read_unlock()
152 * operations.
153 *
154 * The following ordering guarantees are offered by this hash table:
155 *
156 * A.1) "read" after "write": if there is ordering between a write and a
157 * later read, then the read is guaranteed to see the write or some
158 * later write.
159 * A.2) "read traversal" after "write": given that there is dependency
160 * ordering between reads in a "read traversal", if there is
161 * ordering between a write and the first read of the traversal,
162 * then the "read traversal" is guaranteed to see the write or
163 * some later write.
164 * B.1) "write" after "read": if there is ordering between a read and a
165 * later write, then the read will never see the write.
166 * B.2) "write" after "read traversal": given that there is dependency
167 * ordering between reads in a "read traversal", if there is
168 * ordering between the last read of the traversal and a later
169 * write, then the "read traversal" will never see the write.
170 * C) "write" while "read traversal": if a write occurs during a "read
171 * traversal", the traversal may, or may not, see the write.
172 * D.1) "write" after "write": if there is ordering between a write and
173 * a later write, then the later write is guaranteed to see the
174 * effects of the first write.
175 * D.2) Concurrent "write" pairs: The system will assign an arbitrary
176 * order to any pair of concurrent conflicting writes.
177 * Non-conflicting writes (for example, to different keys) are
178 * unordered.
179 * E) If a grace period separates a "del" or "replace" operation
180 * and a subsequent operation, then that subsequent operation is
181 * guaranteed not to see the removed item.
182 * F) Uniqueness guarantee: given a hash table that does not contain
183 * duplicate items for a given key, there will only be one item in
184 * the hash table after an arbitrary sequence of add_unique and/or
185 * add_replace operations. Note, however, that a pair of
186 * concurrent read operations might well access two different items
187 * with that key.
188 * G.1) If a pair of lookups for a given key are ordered (e.g. by a
189 * memory barrier), then the second lookup will return the same
190 * node as the previous lookup, or some later node.
191 * G.2) A "read traversal" that starts after the end of a prior "read
192 * traversal" (ordered by memory barriers) is guaranteed to see the
193 * same nodes as the previous traversal, or some later nodes.
194 * G.3) Concurrent "read" pairs: concurrent reads are unordered. For
195 * example, if a pair of reads to the same key run concurrently
196 * with an insertion of that same key, the reads remain unordered
197 * regardless of their return values. In other words, you cannot
198 * rely on the values returned by the reads to deduce ordering.
199 *
200 * Progress guarantees:
201 *
202 * * Reads are wait-free. These operations always move forward in the
203 * hash table linked list, and this list has no loop.
204 * * Writes are lock-free. Any retry loop performed by a write operation
205 * is triggered by progress made within another update operation.
0f5543cb 206 *
1ee8f000 207 * Bucket node tables:
93d46c39 208 *
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209 * hash table hash table the last all bucket node tables
210 * order size bucket node 0 1 2 3 4 5 6(index)
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211 * table size
212 * 0 1 1 1
213 * 1 2 1 1 1
214 * 2 4 2 1 1 2
215 * 3 8 4 1 1 2 4
216 * 4 16 8 1 1 2 4 8
217 * 5 32 16 1 1 2 4 8 16
218 * 6 64 32 1 1 2 4 8 16 32
219 *
1ee8f000 220 * When growing/shrinking, we only focus on the last bucket node table
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221 * which size is (!order ? 1 : (1 << (order -1))).
222 *
223 * Example for growing/shrinking:
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224 * grow hash table from order 5 to 6: init the index=6 bucket node table
225 * shrink hash table from order 6 to 5: fini the index=6 bucket node table
93d46c39 226 *
1475579c 227 * A bit of ascii art explanation:
67ecffc0 228 *
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229 * The order index is the off-by-one compared to the actual power of 2
230 * because we use index 0 to deal with the 0 special-case.
67ecffc0 231 *
1475579c 232 * This shows the nodes for a small table ordered by reversed bits:
67ecffc0 233 *
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234 * bits reverse
235 * 0 000 000
236 * 4 100 001
237 * 2 010 010
238 * 6 110 011
239 * 1 001 100
240 * 5 101 101
241 * 3 011 110
242 * 7 111 111
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243 *
244 * This shows the nodes in order of non-reversed bits, linked by
1475579c 245 * reversed-bit order.
67ecffc0 246 *
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247 * order bits reverse
248 * 0 0 000 000
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249 * 1 | 1 001 100 <-
250 * 2 | | 2 010 010 <- |
f6fdd688 251 * | | | 3 011 110 | <- |
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252 * 3 -> | | | 4 100 001 | |
253 * -> | | 5 101 101 |
254 * -> | 6 110 011
255 * -> 7 111 111
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256 */
257
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258#define _LGPL_SOURCE
259#include <stdlib.h>
e0ba718a 260#include <errno.h>
e0ba718a 261#include <stdio.h>
abc490a1 262#include <stdint.h>
f000907d 263#include <string.h>
125f41db 264#include <sched.h>
95747f9e 265#include <unistd.h>
e0ba718a 266
a47dd11c 267#include "compat-getcpu.h"
01477510 268#include <urcu/assert.h>
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269#include <urcu/pointer.h>
270#include <urcu/call-rcu.h>
271#include <urcu/flavor.h>
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272#include <urcu/arch.h>
273#include <urcu/uatomic.h>
a42cc659 274#include <urcu/compiler.h>
abc490a1 275#include <urcu/rculfhash.h>
1a990de3 276#include <urcu/static/urcu-signal-nr.h>
0b6aa001 277#include <rculfhash-internal.h>
5e28c532 278#include <stdio.h>
464a1ec9 279#include <pthread.h>
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280#include <signal.h>
281#include "workqueue.h"
282#include "urcu-die.h"
83e334d0 283#include "urcu-utils.h"
44395fb7 284
f8994aee 285/*
4c42f1b8 286 * Split-counters lazily update the global counter each 1024
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287 * addition/removal. It automatically keeps track of resize required.
288 * We use the bucket length as indicator for need to expand for small
ffa11a18 289 * tables and machines lacking per-cpu data support.
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290 */
291#define COUNT_COMMIT_ORDER 10
4ddbb355 292#define DEFAULT_SPLIT_COUNT_MASK 0xFUL
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293#define CHAIN_LEN_TARGET 1
294#define CHAIN_LEN_RESIZE_THRESHOLD 3
2ed95849 295
cd95516d 296/*
76a73da8 297 * Define the minimum table size.
cd95516d 298 */
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299#define MIN_TABLE_ORDER 0
300#define MIN_TABLE_SIZE (1UL << MIN_TABLE_ORDER)
cd95516d 301
b7d619b0 302/*
1ee8f000 303 * Minimum number of bucket nodes to touch per thread to parallelize grow/shrink.
b7d619b0 304 */
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305#define MIN_PARTITION_PER_THREAD_ORDER 12
306#define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
b7d619b0 307
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308/*
309 * The removed flag needs to be updated atomically with the pointer.
48ed1c18 310 * It indicates that no node must attach to the node scheduled for
b198f0fd 311 * removal, and that node garbage collection must be performed.
1ee8f000 312 * The bucket flag does not require to be updated atomically with the
d95bd160 313 * pointer, but it is added as a pointer low bit flag to save space.
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314 * The "removal owner" flag is used to detect which of the "del"
315 * operation that has set the "removed flag" gets to return the removed
316 * node to its caller. Note that the replace operation does not need to
317 * iteract with the "removal owner" flag, because it validates that
318 * the "removed" flag is not set before performing its cmpxchg.
d95bd160 319 */
d37166c6 320#define REMOVED_FLAG (1UL << 0)
1ee8f000 321#define BUCKET_FLAG (1UL << 1)
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322#define REMOVAL_OWNER_FLAG (1UL << 2)
323#define FLAGS_MASK ((1UL << 3) - 1)
d37166c6 324
bb7b2f26 325/* Value of the end pointer. Should not interact with flags. */
f9c80341 326#define END_VALUE NULL
bb7b2f26 327
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328/*
329 * ht_items_count: Split-counters counting the number of node addition
330 * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
331 * is set at hash table creation.
332 *
333 * These are free-running counters, never reset to zero. They count the
334 * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
335 * operations to update the global counter. We choose a power-of-2 value
336 * for the trigger to deal with 32 or 64-bit overflow of the counter.
337 */
df44348d 338struct ht_items_count {
860d07e8 339 unsigned long add, del;
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340} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
341
7f52427b 342/*
d0ec0ed2 343 * resize_work: Contains arguments passed to worker thread
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344 * responsible for performing lazy resize.
345 */
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346struct resize_work {
347 struct urcu_work work;
14044b37 348 struct cds_lfht *ht;
abc490a1 349};
2ed95849 350
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351/*
352 * partition_resize_work: Contains arguments passed to worker threads
353 * executing the hash table resize on partitions of the hash table
354 * assigned to each processor's worker thread.
355 */
b7d619b0 356struct partition_resize_work {
1af6e26e 357 pthread_t thread_id;
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358 struct cds_lfht *ht;
359 unsigned long i, start, len;
360 void (*fct)(struct cds_lfht *ht, unsigned long i,
361 unsigned long start, unsigned long len);
362};
363
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364static struct urcu_workqueue *cds_lfht_workqueue;
365static unsigned long cds_lfht_workqueue_user_count;
366
367/*
368 * Mutex ensuring mutual exclusion between workqueue initialization and
369 * fork handlers. cds_lfht_fork_mutex nests inside call_rcu_mutex.
370 */
371static pthread_mutex_t cds_lfht_fork_mutex = PTHREAD_MUTEX_INITIALIZER;
372
373static struct urcu_atfork cds_lfht_atfork;
374
375/*
376 * atfork handler nesting counters. Handle being registered to many urcu
377 * flavors, thus being possibly invoked more than once in the
378 * pthread_atfork list of callbacks.
379 */
380static int cds_lfht_workqueue_atfork_nesting;
381
382static void cds_lfht_init_worker(const struct rcu_flavor_struct *flavor);
383static void cds_lfht_fini_worker(const struct rcu_flavor_struct *flavor);
384
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385#ifdef CONFIG_CDS_LFHT_ITER_DEBUG
386
387static
388void cds_lfht_iter_debug_set_ht(struct cds_lfht *ht, struct cds_lfht_iter *iter)
389{
390 iter->lfht = ht;
391}
392
01477510 393#define cds_lfht_iter_debug_assert(...) urcu_posix_assert(__VA_ARGS__)
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394
395#else
396
397static
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398void cds_lfht_iter_debug_set_ht(struct cds_lfht *ht __attribute__((unused)),
399 struct cds_lfht_iter *iter __attribute__((unused)))
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400{
401}
402
403#define cds_lfht_iter_debug_assert(...)
404
405#endif
406
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407/*
408 * Algorithm to reverse bits in a word by lookup table, extended to
409 * 64-bit words.
f9830efd 410 * Source:
abc490a1 411 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
f9830efd 412 * Originally from Public Domain.
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413 */
414
67ecffc0 415static const uint8_t BitReverseTable256[256] =
2ed95849 416{
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417#define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
418#define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
419#define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
420 R6(0), R6(2), R6(1), R6(3)
421};
422#undef R2
423#undef R4
424#undef R6
2ed95849 425
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426static
427uint8_t bit_reverse_u8(uint8_t v)
428{
429 return BitReverseTable256[v];
430}
ab7d5fc6 431
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432#if (CAA_BITS_PER_LONG == 32)
433static
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434uint32_t bit_reverse_u32(uint32_t v)
435{
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436 return ((uint32_t) bit_reverse_u8(v) << 24) |
437 ((uint32_t) bit_reverse_u8(v >> 8) << 16) |
438 ((uint32_t) bit_reverse_u8(v >> 16) << 8) |
abc490a1 439 ((uint32_t) bit_reverse_u8(v >> 24));
2ed95849 440}
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441#else
442static
abc490a1 443uint64_t bit_reverse_u64(uint64_t v)
2ed95849 444{
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445 return ((uint64_t) bit_reverse_u8(v) << 56) |
446 ((uint64_t) bit_reverse_u8(v >> 8) << 48) |
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447 ((uint64_t) bit_reverse_u8(v >> 16) << 40) |
448 ((uint64_t) bit_reverse_u8(v >> 24) << 32) |
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449 ((uint64_t) bit_reverse_u8(v >> 32) << 24) |
450 ((uint64_t) bit_reverse_u8(v >> 40) << 16) |
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451 ((uint64_t) bit_reverse_u8(v >> 48) << 8) |
452 ((uint64_t) bit_reverse_u8(v >> 56));
453}
95bc7fb9 454#endif
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455
456static
457unsigned long bit_reverse_ulong(unsigned long v)
458{
459#if (CAA_BITS_PER_LONG == 32)
460 return bit_reverse_u32(v);
461#else
462 return bit_reverse_u64(v);
463#endif
464}
465
f9830efd 466/*
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467 * fls: returns the position of the most significant bit.
468 * Returns 0 if no bit is set, else returns the position of the most
469 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
f9830efd 470 */
0b1e236d 471#if defined(URCU_ARCH_X86)
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472static inline
473unsigned int fls_u32(uint32_t x)
f9830efd 474{
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475 int r;
476
e1789ce2 477 __asm__ ("bsrl %1,%0\n\t"
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478 "jnz 1f\n\t"
479 "movl $-1,%0\n\t"
480 "1:\n\t"
481 : "=r" (r) : "rm" (x));
482 return r + 1;
483}
484#define HAS_FLS_U32
485#endif
486
0b1e236d 487#if defined(URCU_ARCH_AMD64)
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488static inline
489unsigned int fls_u64(uint64_t x)
490{
491 long r;
492
e1789ce2 493 __asm__ ("bsrq %1,%0\n\t"
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494 "jnz 1f\n\t"
495 "movq $-1,%0\n\t"
496 "1:\n\t"
497 : "=r" (r) : "rm" (x));
498 return r + 1;
499}
500#define HAS_FLS_U64
501#endif
502
503#ifndef HAS_FLS_U64
504static __attribute__((unused))
505unsigned int fls_u64(uint64_t x)
506{
507 unsigned int r = 64;
508
509 if (!x)
510 return 0;
511
512 if (!(x & 0xFFFFFFFF00000000ULL)) {
513 x <<= 32;
514 r -= 32;
515 }
516 if (!(x & 0xFFFF000000000000ULL)) {
517 x <<= 16;
518 r -= 16;
519 }
520 if (!(x & 0xFF00000000000000ULL)) {
521 x <<= 8;
522 r -= 8;
523 }
524 if (!(x & 0xF000000000000000ULL)) {
525 x <<= 4;
526 r -= 4;
527 }
528 if (!(x & 0xC000000000000000ULL)) {
529 x <<= 2;
530 r -= 2;
531 }
532 if (!(x & 0x8000000000000000ULL)) {
533 x <<= 1;
534 r -= 1;
535 }
536 return r;
537}
538#endif
539
540#ifndef HAS_FLS_U32
541static __attribute__((unused))
542unsigned int fls_u32(uint32_t x)
543{
544 unsigned int r = 32;
f9830efd 545
24365af7
MD
546 if (!x)
547 return 0;
548 if (!(x & 0xFFFF0000U)) {
549 x <<= 16;
550 r -= 16;
551 }
552 if (!(x & 0xFF000000U)) {
553 x <<= 8;
554 r -= 8;
555 }
556 if (!(x & 0xF0000000U)) {
557 x <<= 4;
558 r -= 4;
559 }
560 if (!(x & 0xC0000000U)) {
561 x <<= 2;
562 r -= 2;
563 }
564 if (!(x & 0x80000000U)) {
565 x <<= 1;
566 r -= 1;
567 }
568 return r;
569}
570#endif
571
5bc6b66f 572unsigned int cds_lfht_fls_ulong(unsigned long x)
f9830efd 573{
6887cc5e 574#if (CAA_BITS_PER_LONG == 32)
24365af7
MD
575 return fls_u32(x);
576#else
577 return fls_u64(x);
578#endif
579}
f9830efd 580
920f8ef6
LJ
581/*
582 * Return the minimum order for which x <= (1UL << order).
583 * Return -1 if x is 0.
584 */
61c3fb60 585static
5bc6b66f 586int cds_lfht_get_count_order_u32(uint32_t x)
24365af7 587{
920f8ef6
LJ
588 if (!x)
589 return -1;
24365af7 590
920f8ef6 591 return fls_u32(x - 1);
24365af7
MD
592}
593
920f8ef6
LJ
594/*
595 * Return the minimum order for which x <= (1UL << order).
596 * Return -1 if x is 0.
597 */
5bc6b66f 598int cds_lfht_get_count_order_ulong(unsigned long x)
24365af7 599{
920f8ef6
LJ
600 if (!x)
601 return -1;
24365af7 602
5bc6b66f 603 return cds_lfht_fls_ulong(x - 1);
f9830efd
MD
604}
605
606static
ab65b890 607void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth);
f9830efd 608
f8994aee 609static
4105056a 610void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
f8994aee
MD
611 unsigned long count);
612
5ffcaeef
MD
613static void mutex_lock(pthread_mutex_t *mutex)
614{
615 int ret;
616
617#ifndef DISTRUST_SIGNALS_EXTREME
618 ret = pthread_mutex_lock(mutex);
619 if (ret)
620 urcu_die(ret);
621#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
622 while ((ret = pthread_mutex_trylock(mutex)) != 0) {
623 if (ret != EBUSY && ret != EINTR)
624 urcu_die(ret);
625 if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) {
626 cmm_smp_mb();
627 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
628 cmm_smp_mb();
629 }
630 (void) poll(NULL, 0, 10);
631 }
632#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
633}
634
635static void mutex_unlock(pthread_mutex_t *mutex)
636{
637 int ret;
638
639 ret = pthread_mutex_unlock(mutex);
640 if (ret)
641 urcu_die(ret);
642}
643
df44348d 644static long nr_cpus_mask = -1;
4c42f1b8 645static long split_count_mask = -1;
e53ab1eb 646static int split_count_order = -1;
4c42f1b8 647
4ddbb355 648#if defined(HAVE_SYSCONF)
4c42f1b8
LJ
649static void ht_init_nr_cpus_mask(void)
650{
651 long maxcpus;
652
653 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
654 if (maxcpus <= 0) {
655 nr_cpus_mask = -2;
656 return;
657 }
658 /*
659 * round up number of CPUs to next power of two, so we
660 * can use & for modulo.
661 */
5bc6b66f 662 maxcpus = 1UL << cds_lfht_get_count_order_ulong(maxcpus);
4c42f1b8
LJ
663 nr_cpus_mask = maxcpus - 1;
664}
4ddbb355
LJ
665#else /* #if defined(HAVE_SYSCONF) */
666static void ht_init_nr_cpus_mask(void)
667{
668 nr_cpus_mask = -2;
669}
670#endif /* #else #if defined(HAVE_SYSCONF) */
df44348d
MD
671
672static
5afadd12 673void alloc_split_items_count(struct cds_lfht *ht)
df44348d 674{
4c42f1b8
LJ
675 if (nr_cpus_mask == -1) {
676 ht_init_nr_cpus_mask();
4ddbb355
LJ
677 if (nr_cpus_mask < 0)
678 split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
679 else
680 split_count_mask = nr_cpus_mask;
e53ab1eb
MD
681 split_count_order =
682 cds_lfht_get_count_order_ulong(split_count_mask + 1);
df44348d 683 }
4c42f1b8 684
01477510 685 urcu_posix_assert(split_count_mask >= 0);
5afadd12
LJ
686
687 if (ht->flags & CDS_LFHT_ACCOUNTING) {
95bc7fb9
MD
688 ht->split_count = calloc(split_count_mask + 1,
689 sizeof(struct ht_items_count));
01477510 690 urcu_posix_assert(ht->split_count);
5afadd12
LJ
691 } else {
692 ht->split_count = NULL;
693 }
df44348d
MD
694}
695
696static
5afadd12 697void free_split_items_count(struct cds_lfht *ht)
df44348d 698{
5afadd12 699 poison_free(ht->split_count);
df44348d
MD
700}
701
702static
14360f1c 703int ht_get_split_count_index(unsigned long hash)
df44348d
MD
704{
705 int cpu;
706
01477510 707 urcu_posix_assert(split_count_mask >= 0);
a47dd11c 708 cpu = urcu_sched_getcpu();
8ed51e04 709 if (caa_unlikely(cpu < 0))
14360f1c 710 return hash & split_count_mask;
df44348d 711 else
4c42f1b8 712 return cpu & split_count_mask;
df44348d
MD
713}
714
715static
14360f1c 716void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash)
df44348d 717{
83e334d0 718 unsigned long split_count, count;
4c42f1b8 719 int index;
df44348d 720
8ed51e04 721 if (caa_unlikely(!ht->split_count))
3171717f 722 return;
14360f1c 723 index = ht_get_split_count_index(hash);
4c42f1b8 724 split_count = uatomic_add_return(&ht->split_count[index].add, 1);
314558bf
MD
725 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
726 return;
727 /* Only if number of add multiple of 1UL << COUNT_COMMIT_ORDER */
728
729 dbg_printf("add split count %lu\n", split_count);
730 count = uatomic_add_return(&ht->count,
731 1UL << COUNT_COMMIT_ORDER);
4c299dcb 732 if (caa_likely(count & (count - 1)))
314558bf
MD
733 return;
734 /* Only if global count is power of 2 */
735
736 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) < size)
737 return;
83e334d0 738 dbg_printf("add set global %lu\n", count);
314558bf
MD
739 cds_lfht_resize_lazy_count(ht, size,
740 count >> (CHAIN_LEN_TARGET - 1));
df44348d
MD
741}
742
743static
14360f1c 744void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
df44348d 745{
83e334d0 746 unsigned long split_count, count;
4c42f1b8 747 int index;
df44348d 748
8ed51e04 749 if (caa_unlikely(!ht->split_count))
3171717f 750 return;
14360f1c 751 index = ht_get_split_count_index(hash);
4c42f1b8 752 split_count = uatomic_add_return(&ht->split_count[index].del, 1);
314558bf
MD
753 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
754 return;
755 /* Only if number of deletes multiple of 1UL << COUNT_COMMIT_ORDER */
756
757 dbg_printf("del split count %lu\n", split_count);
758 count = uatomic_add_return(&ht->count,
759 -(1UL << COUNT_COMMIT_ORDER));
4c299dcb 760 if (caa_likely(count & (count - 1)))
314558bf
MD
761 return;
762 /* Only if global count is power of 2 */
763
764 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) >= size)
765 return;
766 dbg_printf("del set global %ld\n", count);
767 /*
768 * Don't shrink table if the number of nodes is below a
769 * certain threshold.
770 */
771 if (count < (1UL << COUNT_COMMIT_ORDER) * (split_count_mask + 1))
772 return;
773 cds_lfht_resize_lazy_count(ht, size,
774 count >> (CHAIN_LEN_TARGET - 1));
df44348d
MD
775}
776
f9830efd 777static
4105056a 778void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
f9830efd 779{
f8994aee
MD
780 unsigned long count;
781
b8af5011
MD
782 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
783 return;
f8994aee
MD
784 count = uatomic_read(&ht->count);
785 /*
786 * Use bucket-local length for small table expand and for
787 * environments lacking per-cpu data support.
788 */
e53ab1eb 789 if (count >= (1UL << (COUNT_COMMIT_ORDER + split_count_order)))
f8994aee 790 return;
24365af7 791 if (chain_len > 100)
f0c29ed7 792 dbg_printf("WARNING: large chain length: %u.\n",
24365af7 793 chain_len);
e53ab1eb
MD
794 if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD) {
795 int growth;
796
797 /*
798 * Ideal growth calculated based on chain length.
799 */
800 growth = cds_lfht_get_count_order_u32(chain_len
801 - (CHAIN_LEN_TARGET - 1));
802 if ((ht->flags & CDS_LFHT_ACCOUNTING)
803 && (size << growth)
804 >= (1UL << (COUNT_COMMIT_ORDER
805 + split_count_order))) {
806 /*
807 * If ideal growth expands the hash table size
808 * beyond the "small hash table" sizes, use the
809 * maximum small hash table size to attempt
810 * expanding the hash table. This only applies
811 * when node accounting is available, otherwise
812 * the chain length is used to expand the hash
813 * table in every case.
814 */
815 growth = COUNT_COMMIT_ORDER + split_count_order
816 - cds_lfht_get_count_order_ulong(size);
817 if (growth <= 0)
818 return;
819 }
820 cds_lfht_resize_lazy_grow(ht, size, growth);
821 }
f9830efd
MD
822}
823
abc490a1 824static
14044b37 825struct cds_lfht_node *clear_flag(struct cds_lfht_node *node)
abc490a1 826{
14044b37 827 return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK);
abc490a1
MD
828}
829
830static
afa5940d 831int is_removed(const struct cds_lfht_node *node)
abc490a1 832{
d37166c6 833 return ((unsigned long) node) & REMOVED_FLAG;
abc490a1
MD
834}
835
f5596c94 836static
1ee8f000 837int is_bucket(struct cds_lfht_node *node)
f5596c94 838{
1ee8f000 839 return ((unsigned long) node) & BUCKET_FLAG;
f5596c94
MD
840}
841
842static
1ee8f000 843struct cds_lfht_node *flag_bucket(struct cds_lfht_node *node)
f5596c94 844{
1ee8f000 845 return (struct cds_lfht_node *) (((unsigned long) node) | BUCKET_FLAG);
f5596c94 846}
bb7b2f26 847
db00ccc3
MD
848static
849int is_removal_owner(struct cds_lfht_node *node)
850{
851 return ((unsigned long) node) & REMOVAL_OWNER_FLAG;
852}
853
854static
855struct cds_lfht_node *flag_removal_owner(struct cds_lfht_node *node)
856{
857 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVAL_OWNER_FLAG);
858}
859
71bb3aca
MD
860static
861struct cds_lfht_node *flag_removed_or_removal_owner(struct cds_lfht_node *node)
862{
863 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG | REMOVAL_OWNER_FLAG);
864}
865
bb7b2f26
MD
866static
867struct cds_lfht_node *get_end(void)
868{
869 return (struct cds_lfht_node *) END_VALUE;
870}
871
872static
873int is_end(struct cds_lfht_node *node)
874{
875 return clear_flag(node) == (struct cds_lfht_node *) END_VALUE;
876}
877
abc490a1 878static
ab65b890
LJ
879unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr,
880 unsigned long v)
abc490a1
MD
881{
882 unsigned long old1, old2;
883
884 old1 = uatomic_read(ptr);
885 do {
886 old2 = old1;
887 if (old2 >= v)
f9830efd 888 return old2;
abc490a1 889 } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
ab65b890 890 return old2;
abc490a1
MD
891}
892
48f1b16d
LJ
893static
894void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
895{
0b6aa001 896 return ht->mm->alloc_bucket_table(ht, order);
48f1b16d
LJ
897}
898
899/*
900 * cds_lfht_free_bucket_table() should be called with decreasing order.
901 * When cds_lfht_free_bucket_table(0) is called, it means the whole
902 * lfht is destroyed.
903 */
904static
905void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order)
906{
0b6aa001 907 return ht->mm->free_bucket_table(ht, order);
48f1b16d
LJ
908}
909
9d72a73f
LJ
910static inline
911struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
f4a9cc0b 912{
0b6aa001 913 return ht->bucket_at(ht, index);
f4a9cc0b
LJ
914}
915
9d72a73f
LJ
916static inline
917struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
918 unsigned long hash)
919{
01477510 920 urcu_posix_assert(size > 0);
9d72a73f
LJ
921 return bucket_at(ht, hash & (size - 1));
922}
923
273399de
MD
924/*
925 * Remove all logically deleted nodes from a bucket up to a certain node key.
926 */
927static
1ee8f000 928void _cds_lfht_gc_bucket(struct cds_lfht_node *bucket, struct cds_lfht_node *node)
273399de 929{
14044b37 930 struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
273399de 931
01477510
FD
932 urcu_posix_assert(!is_bucket(bucket));
933 urcu_posix_assert(!is_removed(bucket));
934 urcu_posix_assert(!is_removal_owner(bucket));
935 urcu_posix_assert(!is_bucket(node));
936 urcu_posix_assert(!is_removed(node));
937 urcu_posix_assert(!is_removal_owner(node));
273399de 938 for (;;) {
1ee8f000
LJ
939 iter_prev = bucket;
940 /* We can always skip the bucket node initially */
04db56f8 941 iter = rcu_dereference(iter_prev->next);
01477510
FD
942 urcu_posix_assert(!is_removed(iter));
943 urcu_posix_assert(!is_removal_owner(iter));
944 urcu_posix_assert(iter_prev->reverse_hash <= node->reverse_hash);
bd4db153 945 /*
1ee8f000 946 * We should never be called with bucket (start of chain)
bd4db153
MD
947 * and logically removed node (end of path compression
948 * marker) being the actual same node. This would be a
949 * bug in the algorithm implementation.
950 */
01477510 951 urcu_posix_assert(bucket != node);
273399de 952 for (;;) {
8ed51e04 953 if (caa_unlikely(is_end(iter)))
f9c80341 954 return;
04db56f8 955 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
f9c80341 956 return;
04db56f8 957 next = rcu_dereference(clear_flag(iter)->next);
8ed51e04 958 if (caa_likely(is_removed(next)))
273399de 959 break;
b453eae1 960 iter_prev = clear_flag(iter);
273399de
MD
961 iter = next;
962 }
01477510
FD
963 urcu_posix_assert(!is_removed(iter));
964 urcu_posix_assert(!is_removal_owner(iter));
1ee8f000
LJ
965 if (is_bucket(iter))
966 new_next = flag_bucket(clear_flag(next));
f5596c94
MD
967 else
968 new_next = clear_flag(next);
04db56f8 969 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
273399de
MD
970 }
971}
972
9357c415
MD
973static
974int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
975 struct cds_lfht_node *old_node,
3fb86f26 976 struct cds_lfht_node *old_next,
9357c415
MD
977 struct cds_lfht_node *new_node)
978{
04db56f8 979 struct cds_lfht_node *bucket, *ret_next;
9357c415
MD
980
981 if (!old_node) /* Return -ENOENT if asked to replace NULL node */
7801dadd 982 return -ENOENT;
9357c415 983
01477510
FD
984 urcu_posix_assert(!is_removed(old_node));
985 urcu_posix_assert(!is_removal_owner(old_node));
986 urcu_posix_assert(!is_bucket(old_node));
987 urcu_posix_assert(!is_removed(new_node));
988 urcu_posix_assert(!is_removal_owner(new_node));
989 urcu_posix_assert(!is_bucket(new_node));
990 urcu_posix_assert(new_node != old_node);
3fb86f26 991 for (;;) {
9357c415 992 /* Insert after node to be replaced */
9357c415
MD
993 if (is_removed(old_next)) {
994 /*
995 * Too late, the old node has been removed under us
996 * between lookup and replace. Fail.
997 */
7801dadd 998 return -ENOENT;
9357c415 999 }
01477510
FD
1000 urcu_posix_assert(old_next == clear_flag(old_next));
1001 urcu_posix_assert(new_node != old_next);
71bb3aca
MD
1002 /*
1003 * REMOVAL_OWNER flag is _NEVER_ set before the REMOVED
1004 * flag. It is either set atomically at the same time
1005 * (replace) or after (del).
1006 */
01477510 1007 urcu_posix_assert(!is_removal_owner(old_next));
feda2722 1008 new_node->next = old_next;
9357c415
MD
1009 /*
1010 * Here is the whole trick for lock-free replace: we add
1011 * the replacement node _after_ the node we want to
1012 * replace by atomically setting its next pointer at the
1013 * same time we set its removal flag. Given that
1014 * the lookups/get next use an iterator aware of the
1015 * next pointer, they will either skip the old node due
1016 * to the removal flag and see the new node, or use
1017 * the old node, but will not see the new one.
db00ccc3
MD
1018 * This is a replacement of a node with another node
1019 * that has the same value: we are therefore not
71bb3aca
MD
1020 * removing a value from the hash table. We set both the
1021 * REMOVED and REMOVAL_OWNER flags atomically so we own
1022 * the node after successful cmpxchg.
9357c415 1023 */
04db56f8 1024 ret_next = uatomic_cmpxchg(&old_node->next,
71bb3aca 1025 old_next, flag_removed_or_removal_owner(new_node));
3fb86f26 1026 if (ret_next == old_next)
7801dadd 1027 break; /* We performed the replacement. */
3fb86f26
LJ
1028 old_next = ret_next;
1029 }
9357c415 1030
9357c415
MD
1031 /*
1032 * Ensure that the old node is not visible to readers anymore:
1033 * lookup for the node, and remove it (along with any other
1034 * logically removed node) if found.
1035 */
04db56f8
LJ
1036 bucket = lookup_bucket(ht, size, bit_reverse_ulong(old_node->reverse_hash));
1037 _cds_lfht_gc_bucket(bucket, new_node);
7801dadd 1038
01477510 1039 urcu_posix_assert(is_removed(CMM_LOAD_SHARED(old_node->next)));
7801dadd 1040 return 0;
9357c415
MD
1041}
1042
83beee94
MD
1043/*
1044 * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
1045 * mode. A NULL unique_ret allows creation of duplicate keys.
1046 */
abc490a1 1047static
83beee94 1048void _cds_lfht_add(struct cds_lfht *ht,
91a75cc5 1049 unsigned long hash,
0422d92c 1050 cds_lfht_match_fct match,
996ff57c 1051 const void *key,
83beee94
MD
1052 unsigned long size,
1053 struct cds_lfht_node *node,
1054 struct cds_lfht_iter *unique_ret,
1ee8f000 1055 int bucket_flag)
abc490a1 1056{
14044b37 1057 struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
960c9e4f 1058 *return_node;
04db56f8 1059 struct cds_lfht_node *bucket;
abc490a1 1060
01477510
FD
1061 urcu_posix_assert(!is_bucket(node));
1062 urcu_posix_assert(!is_removed(node));
1063 urcu_posix_assert(!is_removal_owner(node));
91a75cc5 1064 bucket = lookup_bucket(ht, size, hash);
abc490a1 1065 for (;;) {
adc0de68 1066 uint32_t chain_len = 0;
abc490a1 1067
11519af6
MD
1068 /*
1069 * iter_prev points to the non-removed node prior to the
1070 * insert location.
11519af6 1071 */
04db56f8 1072 iter_prev = bucket;
1ee8f000 1073 /* We can always skip the bucket node initially */
04db56f8 1074 iter = rcu_dereference(iter_prev->next);
01477510 1075 urcu_posix_assert(iter_prev->reverse_hash <= node->reverse_hash);
abc490a1 1076 for (;;) {
8ed51e04 1077 if (caa_unlikely(is_end(iter)))
273399de 1078 goto insert;
04db56f8 1079 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
273399de 1080 goto insert;
238cc06e 1081
1ee8f000
LJ
1082 /* bucket node is the first node of the identical-hash-value chain */
1083 if (bucket_flag && clear_flag(iter)->reverse_hash == node->reverse_hash)
194fdbd1 1084 goto insert;
238cc06e 1085
04db56f8 1086 next = rcu_dereference(clear_flag(iter)->next);
8ed51e04 1087 if (caa_unlikely(is_removed(next)))
9dba85be 1088 goto gc_node;
238cc06e
LJ
1089
1090 /* uniquely add */
83beee94 1091 if (unique_ret
1ee8f000 1092 && !is_bucket(next)
04db56f8 1093 && clear_flag(iter)->reverse_hash == node->reverse_hash) {
d7c76f85
MD
1094 struct cds_lfht_iter d_iter = {
1095 .node = node,
1096 .next = iter,
1097#ifdef CONFIG_CDS_LFHT_ITER_DEBUG
1098 .lfht = ht,
1099#endif
1100 };
238cc06e
LJ
1101
1102 /*
1103 * uniquely adding inserts the node as the first
1104 * node of the identical-hash-value node chain.
1105 *
1106 * This semantic ensures no duplicated keys
1107 * should ever be observable in the table
1f67ba50
MD
1108 * (including traversing the table node by
1109 * node by forward iterations)
238cc06e 1110 */
04db56f8 1111 cds_lfht_next_duplicate(ht, match, key, &d_iter);
238cc06e
LJ
1112 if (!d_iter.node)
1113 goto insert;
1114
1115 *unique_ret = d_iter;
83beee94 1116 return;
48ed1c18 1117 }
238cc06e 1118
11519af6 1119 /* Only account for identical reverse hash once */
04db56f8 1120 if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash
1ee8f000 1121 && !is_bucket(next))
4105056a 1122 check_resize(ht, size, ++chain_len);
11519af6 1123 iter_prev = clear_flag(iter);
273399de 1124 iter = next;
abc490a1 1125 }
48ed1c18 1126
273399de 1127 insert:
01477510
FD
1128 urcu_posix_assert(node != clear_flag(iter));
1129 urcu_posix_assert(!is_removed(iter_prev));
1130 urcu_posix_assert(!is_removal_owner(iter_prev));
1131 urcu_posix_assert(!is_removed(iter));
1132 urcu_posix_assert(!is_removal_owner(iter));
1133 urcu_posix_assert(iter_prev != node);
1ee8f000 1134 if (!bucket_flag)
04db56f8 1135 node->next = clear_flag(iter);
f9c80341 1136 else
1ee8f000
LJ
1137 node->next = flag_bucket(clear_flag(iter));
1138 if (is_bucket(iter))
1139 new_node = flag_bucket(node);
f5596c94
MD
1140 else
1141 new_node = node;
04db56f8 1142 if (uatomic_cmpxchg(&iter_prev->next, iter,
48ed1c18 1143 new_node) != iter) {
273399de 1144 continue; /* retry */
48ed1c18 1145 } else {
83beee94 1146 return_node = node;
960c9e4f 1147 goto end;
48ed1c18
MD
1148 }
1149
9dba85be 1150 gc_node:
01477510
FD
1151 urcu_posix_assert(!is_removed(iter));
1152 urcu_posix_assert(!is_removal_owner(iter));
1ee8f000
LJ
1153 if (is_bucket(iter))
1154 new_next = flag_bucket(clear_flag(next));
f5596c94
MD
1155 else
1156 new_next = clear_flag(next);
04db56f8 1157 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
273399de 1158 /* retry */
464a1ec9 1159 }
9357c415 1160end:
83beee94
MD
1161 if (unique_ret) {
1162 unique_ret->node = return_node;
1163 /* unique_ret->next left unset, never used. */
1164 }
abc490a1 1165}
464a1ec9 1166
abc490a1 1167static
860d07e8 1168int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
b65ec430 1169 struct cds_lfht_node *node)
abc490a1 1170{
db00ccc3 1171 struct cds_lfht_node *bucket, *next;
5e28c532 1172
9357c415 1173 if (!node) /* Return -ENOENT if asked to delete NULL node */
743f9143 1174 return -ENOENT;
9357c415 1175
7ec59d3b 1176 /* logically delete the node */
01477510
FD
1177 urcu_posix_assert(!is_bucket(node));
1178 urcu_posix_assert(!is_removed(node));
1179 urcu_posix_assert(!is_removal_owner(node));
48ed1c18 1180
db00ccc3
MD
1181 /*
1182 * We are first checking if the node had previously been
1183 * logically removed (this check is not atomic with setting the
1184 * logical removal flag). Return -ENOENT if the node had
1185 * previously been removed.
1186 */
a85eff52 1187 next = CMM_LOAD_SHARED(node->next); /* next is not dereferenced */
db00ccc3
MD
1188 if (caa_unlikely(is_removed(next)))
1189 return -ENOENT;
01477510 1190 urcu_posix_assert(!is_bucket(next));
196f4fab
MD
1191 /*
1192 * The del operation semantic guarantees a full memory barrier
1193 * before the uatomic_or atomic commit of the deletion flag.
1194 */
1195 cmm_smp_mb__before_uatomic_or();
db00ccc3
MD
1196 /*
1197 * We set the REMOVED_FLAG unconditionally. Note that there may
1198 * be more than one concurrent thread setting this flag.
1199 * Knowing which wins the race will be known after the garbage
1200 * collection phase, stay tuned!
1201 */
1202 uatomic_or(&node->next, REMOVED_FLAG);
7ec59d3b 1203 /* We performed the (logical) deletion. */
7ec59d3b
MD
1204
1205 /*
1206 * Ensure that the node is not visible to readers anymore: lookup for
273399de
MD
1207 * the node, and remove it (along with any other logically removed node)
1208 * if found.
11519af6 1209 */
04db56f8
LJ
1210 bucket = lookup_bucket(ht, size, bit_reverse_ulong(node->reverse_hash));
1211 _cds_lfht_gc_bucket(bucket, node);
743f9143 1212
01477510 1213 urcu_posix_assert(is_removed(CMM_LOAD_SHARED(node->next)));
db00ccc3
MD
1214 /*
1215 * Last phase: atomically exchange node->next with a version
1216 * having "REMOVAL_OWNER_FLAG" set. If the returned node->next
1217 * pointer did _not_ have "REMOVAL_OWNER_FLAG" set, we now own
1218 * the node and win the removal race.
1219 * It is interesting to note that all "add" paths are forbidden
1220 * to change the next pointer starting from the point where the
1221 * REMOVED_FLAG is set, so here using a read, followed by a
1222 * xchg() suffice to guarantee that the xchg() will ever only
1223 * set the "REMOVAL_OWNER_FLAG" (or change nothing if the flag
1224 * was already set).
1225 */
1226 if (!is_removal_owner(uatomic_xchg(&node->next,
1227 flag_removal_owner(node->next))))
1228 return 0;
1229 else
1230 return -ENOENT;
abc490a1 1231}
2ed95849 1232
b7d619b0
MD
1233static
1234void *partition_resize_thread(void *arg)
1235{
1236 struct partition_resize_work *work = arg;
1237
7b17c13e 1238 work->ht->flavor->register_thread();
b7d619b0 1239 work->fct(work->ht, work->i, work->start, work->len);
7b17c13e 1240 work->ht->flavor->unregister_thread();
b7d619b0
MD
1241 return NULL;
1242}
1243
1244static
1245void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
1246 unsigned long len,
1247 void (*fct)(struct cds_lfht *ht, unsigned long i,
1248 unsigned long start, unsigned long len))
1249{
e54ec2f5 1250 unsigned long partition_len, start = 0;
b7d619b0 1251 struct partition_resize_work *work;
83e334d0
MJ
1252 int ret;
1253 unsigned long thread, nr_threads;
b7d619b0 1254
01477510 1255 urcu_posix_assert(nr_cpus_mask != -1);
d7f3ba4c
EW
1256 if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD)
1257 goto fallback;
1258
6083a889
MD
1259 /*
1260 * Note: nr_cpus_mask + 1 is always power of 2.
1261 * We spawn just the number of threads we need to satisfy the minimum
1262 * partition size, up to the number of CPUs in the system.
1263 */
91452a6a 1264 if (nr_cpus_mask > 0) {
83e334d0 1265 nr_threads = min_t(unsigned long, nr_cpus_mask + 1,
91452a6a
MD
1266 len >> MIN_PARTITION_PER_THREAD_ORDER);
1267 } else {
1268 nr_threads = 1;
1269 }
5bc6b66f 1270 partition_len = len >> cds_lfht_get_count_order_ulong(nr_threads);
6083a889 1271 work = calloc(nr_threads, sizeof(*work));
7c75d498
EW
1272 if (!work) {
1273 dbg_printf("error allocating for resize, single-threading\n");
1274 goto fallback;
1275 }
6083a889
MD
1276 for (thread = 0; thread < nr_threads; thread++) {
1277 work[thread].ht = ht;
1278 work[thread].i = i;
1279 work[thread].len = partition_len;
1280 work[thread].start = thread * partition_len;
1281 work[thread].fct = fct;
1af6e26e 1282 ret = pthread_create(&(work[thread].thread_id), ht->resize_attr,
6083a889 1283 partition_resize_thread, &work[thread]);
e54ec2f5
EW
1284 if (ret == EAGAIN) {
1285 /*
1286 * Out of resources: wait and join the threads
1287 * we've created, then handle leftovers.
1288 */
1289 dbg_printf("error spawning for resize, single-threading\n");
1290 start = work[thread].start;
1291 len -= start;
1292 nr_threads = thread;
1293 break;
1294 }
01477510 1295 urcu_posix_assert(!ret);
b7d619b0 1296 }
6083a889 1297 for (thread = 0; thread < nr_threads; thread++) {
1af6e26e 1298 ret = pthread_join(work[thread].thread_id, NULL);
01477510 1299 urcu_posix_assert(!ret);
b7d619b0
MD
1300 }
1301 free(work);
e54ec2f5
EW
1302
1303 /*
1304 * A pthread_create failure above will either lead in us having
1305 * no threads to join or starting at a non-zero offset,
1306 * fallback to single thread processing of leftovers.
1307 */
1308 if (start == 0 && nr_threads > 0)
1309 return;
7c75d498 1310fallback:
e54ec2f5 1311 fct(ht, i, start, len);
b7d619b0
MD
1312}
1313
e8de508e
MD
1314/*
1315 * Holding RCU read lock to protect _cds_lfht_add against memory
d0ec0ed2 1316 * reclaim that could be performed by other worker threads (ABA
e8de508e 1317 * problem).
9ee0fc9a 1318 *
b7d619b0 1319 * When we reach a certain length, we can split this population phase over
9ee0fc9a
MD
1320 * many worker threads, based on the number of CPUs available in the system.
1321 * This should therefore take care of not having the expand lagging behind too
1322 * many concurrent insertion threads by using the scheduler's ability to
1ee8f000 1323 * schedule bucket node population fairly with insertions.
e8de508e 1324 */
4105056a 1325static
b7d619b0
MD
1326void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
1327 unsigned long start, unsigned long len)
4105056a 1328{
9d72a73f 1329 unsigned long j, size = 1UL << (i - 1);
4105056a 1330
01477510 1331 urcu_posix_assert(i > MIN_TABLE_ORDER);
7b17c13e 1332 ht->flavor->read_lock();
9d72a73f
LJ
1333 for (j = size + start; j < size + start + len; j++) {
1334 struct cds_lfht_node *new_node = bucket_at(ht, j);
1335
01477510 1336 urcu_posix_assert(j >= size && j < (size << 1));
9d72a73f
LJ
1337 dbg_printf("init populate: order %lu index %lu hash %lu\n",
1338 i, j, j);
1339 new_node->reverse_hash = bit_reverse_ulong(j);
91a75cc5 1340 _cds_lfht_add(ht, j, NULL, NULL, size, new_node, NULL, 1);
4105056a 1341 }
7b17c13e 1342 ht->flavor->read_unlock();
b7d619b0
MD
1343}
1344
1345static
1346void init_table_populate(struct cds_lfht *ht, unsigned long i,
1347 unsigned long len)
1348{
b7d619b0 1349 partition_resize_helper(ht, i, len, init_table_populate_partition);
4105056a
MD
1350}
1351
abc490a1 1352static
4105056a 1353void init_table(struct cds_lfht *ht,
93d46c39 1354 unsigned long first_order, unsigned long last_order)
24365af7 1355{
93d46c39 1356 unsigned long i;
24365af7 1357
93d46c39
LJ
1358 dbg_printf("init table: first_order %lu last_order %lu\n",
1359 first_order, last_order);
01477510 1360 urcu_posix_assert(first_order > MIN_TABLE_ORDER);
93d46c39 1361 for (i = first_order; i <= last_order; i++) {
4105056a 1362 unsigned long len;
24365af7 1363
4f6e90b7 1364 len = 1UL << (i - 1);
f0c29ed7 1365 dbg_printf("init order %lu len: %lu\n", i, len);
4d676753
MD
1366
1367 /* Stop expand if the resize target changes under us */
7b3893e4 1368 if (CMM_LOAD_SHARED(ht->resize_target) < (1UL << i))
4d676753
MD
1369 break;
1370
48f1b16d 1371 cds_lfht_alloc_bucket_table(ht, i);
4105056a 1372
4105056a 1373 /*
1ee8f000
LJ
1374 * Set all bucket nodes reverse hash values for a level and
1375 * link all bucket nodes into the table.
4105056a 1376 */
dc1da8f6 1377 init_table_populate(ht, i, len);
4105056a 1378
f9c80341
MD
1379 /*
1380 * Update table size.
1381 */
1382 cmm_smp_wmb(); /* populate data before RCU size */
7b3893e4 1383 CMM_STORE_SHARED(ht->size, 1UL << i);
f9c80341 1384
4f6e90b7 1385 dbg_printf("init new size: %lu\n", 1UL << i);
4105056a
MD
1386 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1387 break;
1388 }
1389}
1390
e8de508e
MD
1391/*
1392 * Holding RCU read lock to protect _cds_lfht_remove against memory
d0ec0ed2 1393 * reclaim that could be performed by other worker threads (ABA
e8de508e
MD
1394 * problem).
1395 * For a single level, we logically remove and garbage collect each node.
1396 *
1397 * As a design choice, we perform logical removal and garbage collection on a
1398 * node-per-node basis to simplify this algorithm. We also assume keeping good
1399 * cache locality of the operation would overweight possible performance gain
1400 * that could be achieved by batching garbage collection for multiple levels.
1401 * However, this would have to be justified by benchmarks.
1402 *
1403 * Concurrent removal and add operations are helping us perform garbage
1404 * collection of logically removed nodes. We guarantee that all logically
d0ec0ed2
MD
1405 * removed nodes have been garbage-collected (unlinked) before work
1406 * enqueue is invoked to free a hole level of bucket nodes (after a
1407 * grace period).
e8de508e 1408 *
1f67ba50
MD
1409 * Logical removal and garbage collection can therefore be done in batch
1410 * or on a node-per-node basis, as long as the guarantee above holds.
9ee0fc9a 1411 *
b7d619b0
MD
1412 * When we reach a certain length, we can split this removal over many worker
1413 * threads, based on the number of CPUs available in the system. This should
1414 * take care of not letting resize process lag behind too many concurrent
9ee0fc9a 1415 * updater threads actively inserting into the hash table.
e8de508e 1416 */
4105056a 1417static
b7d619b0
MD
1418void remove_table_partition(struct cds_lfht *ht, unsigned long i,
1419 unsigned long start, unsigned long len)
4105056a 1420{
9d72a73f 1421 unsigned long j, size = 1UL << (i - 1);
4105056a 1422
01477510 1423 urcu_posix_assert(i > MIN_TABLE_ORDER);
7b17c13e 1424 ht->flavor->read_lock();
9d72a73f 1425 for (j = size + start; j < size + start + len; j++) {
2e2ce1e9
LJ
1426 struct cds_lfht_node *fini_bucket = bucket_at(ht, j);
1427 struct cds_lfht_node *parent_bucket = bucket_at(ht, j - size);
9d72a73f 1428
01477510 1429 urcu_posix_assert(j >= size && j < (size << 1));
9d72a73f
LJ
1430 dbg_printf("remove entry: order %lu index %lu hash %lu\n",
1431 i, j, j);
2e2ce1e9
LJ
1432 /* Set the REMOVED_FLAG to freeze the ->next for gc */
1433 uatomic_or(&fini_bucket->next, REMOVED_FLAG);
1434 _cds_lfht_gc_bucket(parent_bucket, fini_bucket);
abc490a1 1435 }
7b17c13e 1436 ht->flavor->read_unlock();
b7d619b0
MD
1437}
1438
1439static
1440void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
1441{
b7d619b0 1442 partition_resize_helper(ht, i, len, remove_table_partition);
2ed95849
MD
1443}
1444
61adb337
MD
1445/*
1446 * fini_table() is never called for first_order == 0, which is why
1447 * free_by_rcu_order == 0 can be used as criterion to know if free must
1448 * be called.
1449 */
1475579c 1450static
4105056a 1451void fini_table(struct cds_lfht *ht,
93d46c39 1452 unsigned long first_order, unsigned long last_order)
1475579c 1453{
83e334d0 1454 unsigned long free_by_rcu_order = 0, i;
1475579c 1455
93d46c39
LJ
1456 dbg_printf("fini table: first_order %lu last_order %lu\n",
1457 first_order, last_order);
01477510 1458 urcu_posix_assert(first_order > MIN_TABLE_ORDER);
93d46c39 1459 for (i = last_order; i >= first_order; i--) {
4105056a 1460 unsigned long len;
1475579c 1461
4f6e90b7 1462 len = 1UL << (i - 1);
e15df1cc 1463 dbg_printf("fini order %ld len: %lu\n", i, len);
4105056a 1464
4d676753 1465 /* Stop shrink if the resize target changes under us */
7b3893e4 1466 if (CMM_LOAD_SHARED(ht->resize_target) > (1UL << (i - 1)))
4d676753
MD
1467 break;
1468
1469 cmm_smp_wmb(); /* populate data before RCU size */
7b3893e4 1470 CMM_STORE_SHARED(ht->size, 1UL << (i - 1));
4d676753
MD
1471
1472 /*
1473 * We need to wait for all add operations to reach Q.S. (and
1474 * thus use the new table for lookups) before we can start
1ee8f000 1475 * releasing the old bucket nodes. Otherwise their lookup will
4d676753
MD
1476 * return a logically removed node as insert position.
1477 */
7b17c13e 1478 ht->flavor->update_synchronize_rcu();
48f1b16d
LJ
1479 if (free_by_rcu_order)
1480 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
4d676753 1481
21263e21 1482 /*
1ee8f000
LJ
1483 * Set "removed" flag in bucket nodes about to be removed.
1484 * Unlink all now-logically-removed bucket node pointers.
4105056a
MD
1485 * Concurrent add/remove operation are helping us doing
1486 * the gc.
21263e21 1487 */
4105056a
MD
1488 remove_table(ht, i, len);
1489
48f1b16d 1490 free_by_rcu_order = i;
4105056a
MD
1491
1492 dbg_printf("fini new size: %lu\n", 1UL << i);
1475579c
MD
1493 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1494 break;
1495 }
0d14ceb2 1496
48f1b16d 1497 if (free_by_rcu_order) {
7b17c13e 1498 ht->flavor->update_synchronize_rcu();
48f1b16d 1499 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
0d14ceb2 1500 }
1475579c
MD
1501}
1502
83e334d0
MJ
1503/*
1504 * Never called with size < 1.
1505 */
ff0d69de 1506static
1ee8f000 1507void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size)
ff0d69de 1508{
04db56f8 1509 struct cds_lfht_node *prev, *node;
9d72a73f 1510 unsigned long order, len, i;
83e334d0 1511 int bucket_order;
ff0d69de 1512
48f1b16d 1513 cds_lfht_alloc_bucket_table(ht, 0);
ff0d69de 1514
9d72a73f
LJ
1515 dbg_printf("create bucket: order 0 index 0 hash 0\n");
1516 node = bucket_at(ht, 0);
1517 node->next = flag_bucket(get_end());
1518 node->reverse_hash = 0;
ff0d69de 1519
83e334d0 1520 bucket_order = cds_lfht_get_count_order_ulong(size);
01477510 1521 urcu_posix_assert(bucket_order >= 0);
83e334d0
MJ
1522
1523 for (order = 1; order < (unsigned long) bucket_order + 1; order++) {
ff0d69de 1524 len = 1UL << (order - 1);
48f1b16d 1525 cds_lfht_alloc_bucket_table(ht, order);
ff0d69de 1526
9d72a73f
LJ
1527 for (i = 0; i < len; i++) {
1528 /*
1529 * Now, we are trying to init the node with the
1530 * hash=(len+i) (which is also a bucket with the
1531 * index=(len+i)) and insert it into the hash table,
1532 * so this node has to be inserted after the bucket
1533 * with the index=(len+i)&(len-1)=i. And because there
1534 * is no other non-bucket node nor bucket node with
1535 * larger index/hash inserted, so the bucket node
1536 * being inserted should be inserted directly linked
1537 * after the bucket node with index=i.
1538 */
1539 prev = bucket_at(ht, i);
1540 node = bucket_at(ht, len + i);
ff0d69de 1541
1ee8f000 1542 dbg_printf("create bucket: order %lu index %lu hash %lu\n",
9d72a73f
LJ
1543 order, len + i, len + i);
1544 node->reverse_hash = bit_reverse_ulong(len + i);
1545
1546 /* insert after prev */
01477510 1547 urcu_posix_assert(is_bucket(prev->next));
ff0d69de 1548 node->next = prev->next;
1ee8f000 1549 prev->next = flag_bucket(node);
ff0d69de
LJ
1550 }
1551 }
1552}
1553
99ab1528
MJ
1554#if (CAA_BITS_PER_LONG > 32)
1555/*
1556 * For 64-bit architectures, with max number of buckets small enough not to
1557 * use the entire 64-bit memory mapping space (and allowing a fair number of
1558 * hash table instances), use the mmap allocator, which is faster. Otherwise,
1559 * fallback to the order allocator.
1560 */
1561static
1562const struct cds_lfht_mm_type *get_mm_type(unsigned long max_nr_buckets)
1563{
1564 if (max_nr_buckets && max_nr_buckets <= (1ULL << 32))
1565 return &cds_lfht_mm_mmap;
1566 else
1567 return &cds_lfht_mm_order;
1568}
1569#else
1570/*
1571 * For 32-bit architectures, use the order allocator.
1572 */
1573static
70469b43
MJ
1574const struct cds_lfht_mm_type *get_mm_type(
1575 unsigned long max_nr_buckets __attribute__((unused)))
99ab1528
MJ
1576{
1577 return &cds_lfht_mm_order;
1578}
1579#endif
1580
0422d92c 1581struct cds_lfht *_cds_lfht_new(unsigned long init_size,
0722081a 1582 unsigned long min_nr_alloc_buckets,
747d725c 1583 unsigned long max_nr_buckets,
b8af5011 1584 int flags,
0b6aa001 1585 const struct cds_lfht_mm_type *mm,
7b17c13e 1586 const struct rcu_flavor_struct *flavor,
b7d619b0 1587 pthread_attr_t *attr)
abc490a1 1588{
14044b37 1589 struct cds_lfht *ht;
24365af7 1590 unsigned long order;
abc490a1 1591
0722081a
LJ
1592 /* min_nr_alloc_buckets must be power of two */
1593 if (!min_nr_alloc_buckets || (min_nr_alloc_buckets & (min_nr_alloc_buckets - 1)))
5488222b 1594 return NULL;
747d725c 1595
8129be4e 1596 /* init_size must be power of two */
5488222b 1597 if (!init_size || (init_size & (init_size - 1)))
8129be4e 1598 return NULL;
747d725c 1599
c1888f3a
MD
1600 /*
1601 * Memory management plugin default.
1602 */
99ab1528
MJ
1603 if (!mm)
1604 mm = get_mm_type(max_nr_buckets);
c1888f3a 1605
0b6aa001
LJ
1606 /* max_nr_buckets == 0 for order based mm means infinite */
1607 if (mm == &cds_lfht_mm_order && !max_nr_buckets)
747d725c
LJ
1608 max_nr_buckets = 1UL << (MAX_TABLE_ORDER - 1);
1609
1610 /* max_nr_buckets must be power of two */
1611 if (!max_nr_buckets || (max_nr_buckets & (max_nr_buckets - 1)))
1612 return NULL;
1613
d0ec0ed2
MD
1614 if (flags & CDS_LFHT_AUTO_RESIZE)
1615 cds_lfht_init_worker(flavor);
1616
0722081a 1617 min_nr_alloc_buckets = max(min_nr_alloc_buckets, MIN_TABLE_SIZE);
d0d8f9aa 1618 init_size = max(init_size, MIN_TABLE_SIZE);
747d725c
LJ
1619 max_nr_buckets = max(max_nr_buckets, min_nr_alloc_buckets);
1620 init_size = min(init_size, max_nr_buckets);
0b6aa001
LJ
1621
1622 ht = mm->alloc_cds_lfht(min_nr_alloc_buckets, max_nr_buckets);
01477510
FD
1623 urcu_posix_assert(ht);
1624 urcu_posix_assert(ht->mm == mm);
1625 urcu_posix_assert(ht->bucket_at == mm->bucket_at);
0b6aa001 1626
b5d6b20f 1627 ht->flags = flags;
7b17c13e 1628 ht->flavor = flavor;
b7d619b0 1629 ht->resize_attr = attr;
5afadd12 1630 alloc_split_items_count(ht);
abc490a1
MD
1631 /* this mutex should not nest in read-side C.S. */
1632 pthread_mutex_init(&ht->resize_mutex, NULL);
5bc6b66f 1633 order = cds_lfht_get_count_order_ulong(init_size);
7b3893e4 1634 ht->resize_target = 1UL << order;
1ee8f000 1635 cds_lfht_create_bucket(ht, 1UL << order);
7b3893e4 1636 ht->size = 1UL << order;
abc490a1
MD
1637 return ht;
1638}
1639
6f554439 1640void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
996ff57c 1641 cds_lfht_match_fct match, const void *key,
6f554439 1642 struct cds_lfht_iter *iter)
2ed95849 1643{
04db56f8 1644 struct cds_lfht_node *node, *next, *bucket;
0422d92c 1645 unsigned long reverse_hash, size;
2ed95849 1646
d7c76f85
MD
1647 cds_lfht_iter_debug_set_ht(ht, iter);
1648
abc490a1 1649 reverse_hash = bit_reverse_ulong(hash);
464a1ec9 1650
7b3893e4 1651 size = rcu_dereference(ht->size);
04db56f8 1652 bucket = lookup_bucket(ht, size, hash);
1ee8f000 1653 /* We can always skip the bucket node initially */
04db56f8 1654 node = rcu_dereference(bucket->next);
bb7b2f26 1655 node = clear_flag(node);
2ed95849 1656 for (;;) {
8ed51e04 1657 if (caa_unlikely(is_end(node))) {
96ad1112 1658 node = next = NULL;
abc490a1 1659 break;
bb7b2f26 1660 }
04db56f8 1661 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
96ad1112 1662 node = next = NULL;
abc490a1 1663 break;
2ed95849 1664 }
04db56f8 1665 next = rcu_dereference(node->next);
01477510 1666 urcu_posix_assert(node == clear_flag(node));
8ed51e04 1667 if (caa_likely(!is_removed(next))
1ee8f000 1668 && !is_bucket(next)
04db56f8 1669 && node->reverse_hash == reverse_hash
0422d92c 1670 && caa_likely(match(node, key))) {
273399de 1671 break;
2ed95849 1672 }
1b81fe1a 1673 node = clear_flag(next);
2ed95849 1674 }
01477510 1675 urcu_posix_assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
adc0de68
MD
1676 iter->node = node;
1677 iter->next = next;
abc490a1 1678}
e0ba718a 1679
70469b43
MJ
1680void cds_lfht_next_duplicate(struct cds_lfht *ht __attribute__((unused)),
1681 cds_lfht_match_fct match,
996ff57c 1682 const void *key, struct cds_lfht_iter *iter)
a481e5ff 1683{
adc0de68 1684 struct cds_lfht_node *node, *next;
a481e5ff 1685 unsigned long reverse_hash;
a481e5ff 1686
d7c76f85 1687 cds_lfht_iter_debug_assert(ht == iter->lfht);
adc0de68 1688 node = iter->node;
04db56f8 1689 reverse_hash = node->reverse_hash;
adc0de68 1690 next = iter->next;
a481e5ff
MD
1691 node = clear_flag(next);
1692
1693 for (;;) {
8ed51e04 1694 if (caa_unlikely(is_end(node))) {
96ad1112 1695 node = next = NULL;
a481e5ff 1696 break;
bb7b2f26 1697 }
04db56f8 1698 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
96ad1112 1699 node = next = NULL;
a481e5ff
MD
1700 break;
1701 }
04db56f8 1702 next = rcu_dereference(node->next);
8ed51e04 1703 if (caa_likely(!is_removed(next))
1ee8f000 1704 && !is_bucket(next)
04db56f8 1705 && caa_likely(match(node, key))) {
a481e5ff
MD
1706 break;
1707 }
1708 node = clear_flag(next);
1709 }
01477510 1710 urcu_posix_assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
adc0de68
MD
1711 iter->node = node;
1712 iter->next = next;
a481e5ff
MD
1713}
1714
70469b43
MJ
1715void cds_lfht_next(struct cds_lfht *ht __attribute__((unused)),
1716 struct cds_lfht_iter *iter)
4e9b9fbf
MD
1717{
1718 struct cds_lfht_node *node, *next;
1719
d7c76f85 1720 cds_lfht_iter_debug_assert(ht == iter->lfht);
853395e1 1721 node = clear_flag(iter->next);
4e9b9fbf 1722 for (;;) {
8ed51e04 1723 if (caa_unlikely(is_end(node))) {
4e9b9fbf
MD
1724 node = next = NULL;
1725 break;
1726 }
04db56f8 1727 next = rcu_dereference(node->next);
8ed51e04 1728 if (caa_likely(!is_removed(next))
1ee8f000 1729 && !is_bucket(next)) {
4e9b9fbf
MD
1730 break;
1731 }
1732 node = clear_flag(next);
1733 }
01477510 1734 urcu_posix_assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
4e9b9fbf
MD
1735 iter->node = node;
1736 iter->next = next;
1737}
1738
1739void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1740{
d7c76f85 1741 cds_lfht_iter_debug_set_ht(ht, iter);
4e9b9fbf 1742 /*
1ee8f000 1743 * Get next after first bucket node. The first bucket node is the
4e9b9fbf
MD
1744 * first node of the linked list.
1745 */
9d72a73f 1746 iter->next = bucket_at(ht, 0)->next;
4e9b9fbf
MD
1747 cds_lfht_next(ht, iter);
1748}
1749
0422d92c
MD
1750void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
1751 struct cds_lfht_node *node)
abc490a1 1752{
0422d92c 1753 unsigned long size;
ab7d5fc6 1754
709bacf9 1755 node->reverse_hash = bit_reverse_ulong(hash);
7b3893e4 1756 size = rcu_dereference(ht->size);
91a75cc5 1757 _cds_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0);
14360f1c 1758 ht_count_add(ht, size, hash);
3eca1b8c
MD
1759}
1760
14044b37 1761struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
6f554439 1762 unsigned long hash,
0422d92c 1763 cds_lfht_match_fct match,
996ff57c 1764 const void *key,
48ed1c18 1765 struct cds_lfht_node *node)
3eca1b8c 1766{
0422d92c 1767 unsigned long size;
83beee94 1768 struct cds_lfht_iter iter;
3eca1b8c 1769
709bacf9 1770 node->reverse_hash = bit_reverse_ulong(hash);
7b3893e4 1771 size = rcu_dereference(ht->size);
91a75cc5 1772 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
83beee94 1773 if (iter.node == node)
14360f1c 1774 ht_count_add(ht, size, hash);
83beee94 1775 return iter.node;
2ed95849
MD
1776}
1777
9357c415 1778struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
6f554439 1779 unsigned long hash,
0422d92c 1780 cds_lfht_match_fct match,
996ff57c 1781 const void *key,
48ed1c18
MD
1782 struct cds_lfht_node *node)
1783{
0422d92c 1784 unsigned long size;
83beee94 1785 struct cds_lfht_iter iter;
48ed1c18 1786
709bacf9 1787 node->reverse_hash = bit_reverse_ulong(hash);
7b3893e4 1788 size = rcu_dereference(ht->size);
83beee94 1789 for (;;) {
91a75cc5 1790 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
83beee94 1791 if (iter.node == node) {
14360f1c 1792 ht_count_add(ht, size, hash);
83beee94
MD
1793 return NULL;
1794 }
1795
1796 if (!_cds_lfht_replace(ht, size, iter.node, iter.next, node))
1797 return iter.node;
1798 }
48ed1c18
MD
1799}
1800
2e79c445
MD
1801int cds_lfht_replace(struct cds_lfht *ht,
1802 struct cds_lfht_iter *old_iter,
1803 unsigned long hash,
1804 cds_lfht_match_fct match,
1805 const void *key,
9357c415
MD
1806 struct cds_lfht_node *new_node)
1807{
1808 unsigned long size;
1809
709bacf9 1810 new_node->reverse_hash = bit_reverse_ulong(hash);
2e79c445
MD
1811 if (!old_iter->node)
1812 return -ENOENT;
1813 if (caa_unlikely(old_iter->node->reverse_hash != new_node->reverse_hash))
1814 return -EINVAL;
1815 if (caa_unlikely(!match(old_iter->node, key)))
1816 return -EINVAL;
7b3893e4 1817 size = rcu_dereference(ht->size);
9357c415
MD
1818 return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next,
1819 new_node);
1820}
1821
bc8c3c74 1822int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
2ed95849 1823{
95bc7fb9 1824 unsigned long size;
df44348d 1825 int ret;
abc490a1 1826
7b3893e4 1827 size = rcu_dereference(ht->size);
bc8c3c74 1828 ret = _cds_lfht_del(ht, size, node);
14360f1c 1829 if (!ret) {
95bc7fb9
MD
1830 unsigned long hash;
1831
bc8c3c74 1832 hash = bit_reverse_ulong(node->reverse_hash);
14360f1c
LJ
1833 ht_count_del(ht, size, hash);
1834 }
df44348d 1835 return ret;
2ed95849 1836}
ab7d5fc6 1837
afa5940d 1838int cds_lfht_is_node_deleted(const struct cds_lfht_node *node)
df55172a 1839{
a85eff52 1840 return is_removed(CMM_LOAD_SHARED(node->next));
df55172a
MD
1841}
1842
abc490a1 1843static
1ee8f000 1844int cds_lfht_delete_bucket(struct cds_lfht *ht)
674f7a69 1845{
14044b37 1846 struct cds_lfht_node *node;
4105056a 1847 unsigned long order, i, size;
674f7a69 1848
abc490a1 1849 /* Check that the table is empty */
9d72a73f 1850 node = bucket_at(ht, 0);
abc490a1 1851 do {
04db56f8 1852 node = clear_flag(node)->next;
1ee8f000 1853 if (!is_bucket(node))
abc490a1 1854 return -EPERM;
01477510
FD
1855 urcu_posix_assert(!is_removed(node));
1856 urcu_posix_assert(!is_removal_owner(node));
bb7b2f26 1857 } while (!is_end(node));
4105056a
MD
1858 /*
1859 * size accessed without rcu_dereference because hash table is
1860 * being destroyed.
1861 */
7b3893e4 1862 size = ht->size;
1f67ba50 1863 /* Internal sanity check: all nodes left should be buckets */
48f1b16d
LJ
1864 for (i = 0; i < size; i++) {
1865 node = bucket_at(ht, i);
1866 dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
1867 i, i, bit_reverse_ulong(node->reverse_hash));
01477510 1868 urcu_posix_assert(is_bucket(node->next));
48f1b16d 1869 }
24365af7 1870
5bc6b66f 1871 for (order = cds_lfht_get_count_order_ulong(size); (long)order >= 0; order--)
48f1b16d 1872 cds_lfht_free_bucket_table(ht, order);
5488222b 1873
abc490a1 1874 return 0;
674f7a69
MD
1875}
1876
1877/*
1878 * Should only be called when no more concurrent readers nor writers can
1879 * possibly access the table.
1880 */
b7d619b0 1881int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
674f7a69 1882{
d0ec0ed2
MD
1883 int ret;
1884
1885 if (ht->flags & CDS_LFHT_AUTO_RESIZE) {
1886 /* Cancel ongoing resize operations. */
1887 _CMM_STORE_SHARED(ht->in_progress_destroy, 1);
1888 /* Wait for in-flight resize operations to complete */
1889 urcu_workqueue_flush_queued_work(cds_lfht_workqueue);
10e68472 1890 }
1ee8f000 1891 ret = cds_lfht_delete_bucket(ht);
abc490a1
MD
1892 if (ret)
1893 return ret;
5afadd12 1894 free_split_items_count(ht);
b7d619b0
MD
1895 if (attr)
1896 *attr = ht->resize_attr;
59629f09
MD
1897 ret = pthread_mutex_destroy(&ht->resize_mutex);
1898 if (ret)
1899 ret = -EBUSY;
d0ec0ed2
MD
1900 if (ht->flags & CDS_LFHT_AUTO_RESIZE)
1901 cds_lfht_fini_worker(ht->flavor);
98808fb1 1902 poison_free(ht);
5e28c532 1903 return ret;
674f7a69
MD
1904}
1905
14044b37 1906void cds_lfht_count_nodes(struct cds_lfht *ht,
d933dd0e 1907 long *approx_before,
273399de 1908 unsigned long *count,
d933dd0e 1909 long *approx_after)
273399de 1910{
14044b37 1911 struct cds_lfht_node *node, *next;
caf3653d 1912 unsigned long nr_bucket = 0, nr_removed = 0;
273399de 1913
7ed7682f 1914 *approx_before = 0;
5afadd12 1915 if (ht->split_count) {
973e5e1b
MD
1916 int i;
1917
4c42f1b8
LJ
1918 for (i = 0; i < split_count_mask + 1; i++) {
1919 *approx_before += uatomic_read(&ht->split_count[i].add);
1920 *approx_before -= uatomic_read(&ht->split_count[i].del);
973e5e1b
MD
1921 }
1922 }
1923
273399de 1924 *count = 0;
273399de 1925
1ee8f000 1926 /* Count non-bucket nodes in the table */
9d72a73f 1927 node = bucket_at(ht, 0);
273399de 1928 do {
04db56f8 1929 next = rcu_dereference(node->next);
b198f0fd 1930 if (is_removed(next)) {
1ee8f000 1931 if (!is_bucket(next))
caf3653d 1932 (nr_removed)++;
973e5e1b 1933 else
1ee8f000
LJ
1934 (nr_bucket)++;
1935 } else if (!is_bucket(next))
273399de 1936 (*count)++;
24365af7 1937 else
1ee8f000 1938 (nr_bucket)++;
273399de 1939 node = clear_flag(next);
bb7b2f26 1940 } while (!is_end(node));
caf3653d 1941 dbg_printf("number of logically removed nodes: %lu\n", nr_removed);
1ee8f000 1942 dbg_printf("number of bucket nodes: %lu\n", nr_bucket);
7ed7682f 1943 *approx_after = 0;
5afadd12 1944 if (ht->split_count) {
973e5e1b
MD
1945 int i;
1946
4c42f1b8
LJ
1947 for (i = 0; i < split_count_mask + 1; i++) {
1948 *approx_after += uatomic_read(&ht->split_count[i].add);
1949 *approx_after -= uatomic_read(&ht->split_count[i].del);
973e5e1b
MD
1950 }
1951 }
273399de
MD
1952}
1953
1475579c 1954/* called with resize mutex held */
abc490a1 1955static
4105056a 1956void _do_cds_lfht_grow(struct cds_lfht *ht,
1475579c 1957 unsigned long old_size, unsigned long new_size)
abc490a1 1958{
1475579c 1959 unsigned long old_order, new_order;
1475579c 1960
5bc6b66f
MD
1961 old_order = cds_lfht_get_count_order_ulong(old_size);
1962 new_order = cds_lfht_get_count_order_ulong(new_size);
1a401918
LJ
1963 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1964 old_size, old_order, new_size, new_order);
01477510 1965 urcu_posix_assert(new_size > old_size);
93d46c39 1966 init_table(ht, old_order + 1, new_order);
abc490a1
MD
1967}
1968
1969/* called with resize mutex held */
1970static
4105056a 1971void _do_cds_lfht_shrink(struct cds_lfht *ht,
1475579c 1972 unsigned long old_size, unsigned long new_size)
464a1ec9 1973{
1475579c 1974 unsigned long old_order, new_order;
464a1ec9 1975
d0d8f9aa 1976 new_size = max(new_size, MIN_TABLE_SIZE);
5bc6b66f
MD
1977 old_order = cds_lfht_get_count_order_ulong(old_size);
1978 new_order = cds_lfht_get_count_order_ulong(new_size);
1a401918
LJ
1979 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1980 old_size, old_order, new_size, new_order);
01477510 1981 urcu_posix_assert(new_size < old_size);
1475579c 1982
1ee8f000 1983 /* Remove and unlink all bucket nodes to remove. */
93d46c39 1984 fini_table(ht, new_order + 1, old_order);
464a1ec9
MD
1985}
1986
1475579c
MD
1987
1988/* called with resize mutex held */
1989static
1990void _do_cds_lfht_resize(struct cds_lfht *ht)
1991{
1992 unsigned long new_size, old_size;
4105056a
MD
1993
1994 /*
1995 * Resize table, re-do if the target size has changed under us.
1996 */
1997 do {
d2be3620
MD
1998 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1999 break;
7b3893e4
LJ
2000 ht->resize_initiated = 1;
2001 old_size = ht->size;
2002 new_size = CMM_LOAD_SHARED(ht->resize_target);
4105056a
MD
2003 if (old_size < new_size)
2004 _do_cds_lfht_grow(ht, old_size, new_size);
2005 else if (old_size > new_size)
2006 _do_cds_lfht_shrink(ht, old_size, new_size);
7b3893e4 2007 ht->resize_initiated = 0;
4105056a
MD
2008 /* write resize_initiated before read resize_target */
2009 cmm_smp_mb();
7b3893e4 2010 } while (ht->size != CMM_LOAD_SHARED(ht->resize_target));
1475579c
MD
2011}
2012
abc490a1 2013static
ab65b890 2014unsigned long resize_target_grow(struct cds_lfht *ht, unsigned long new_size)
464a1ec9 2015{
7b3893e4 2016 return _uatomic_xchg_monotonic_increase(&ht->resize_target, new_size);
464a1ec9
MD
2017}
2018
1475579c 2019static
4105056a 2020void resize_target_update_count(struct cds_lfht *ht,
b8af5011 2021 unsigned long count)
1475579c 2022{
d0d8f9aa 2023 count = max(count, MIN_TABLE_SIZE);
747d725c 2024 count = min(count, ht->max_nr_buckets);
7b3893e4 2025 uatomic_set(&ht->resize_target, count);
1475579c
MD
2026}
2027
2028void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
464a1ec9 2029{
10e68472
MD
2030 resize_target_update_count(ht, new_size);
2031 CMM_STORE_SHARED(ht->resize_initiated, 1);
5ffcaeef 2032 mutex_lock(&ht->resize_mutex);
1475579c 2033 _do_cds_lfht_resize(ht);
5ffcaeef 2034 mutex_unlock(&ht->resize_mutex);
abc490a1 2035}
464a1ec9 2036
abc490a1 2037static
d0ec0ed2 2038void do_resize_cb(struct urcu_work *work)
abc490a1 2039{
d0ec0ed2
MD
2040 struct resize_work *resize_work =
2041 caa_container_of(work, struct resize_work, work);
2042 struct cds_lfht *ht = resize_work->ht;
abc490a1 2043
d0ec0ed2 2044 ht->flavor->register_thread();
5ffcaeef 2045 mutex_lock(&ht->resize_mutex);
14044b37 2046 _do_cds_lfht_resize(ht);
5ffcaeef 2047 mutex_unlock(&ht->resize_mutex);
d0ec0ed2 2048 ht->flavor->unregister_thread();
98808fb1 2049 poison_free(work);
464a1ec9
MD
2050}
2051
abc490a1 2052static
f1f119ee 2053void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht)
ab7d5fc6 2054{
d0ec0ed2 2055 struct resize_work *work;
abc490a1 2056
4105056a
MD
2057 /* Store resize_target before read resize_initiated */
2058 cmm_smp_mb();
7b3893e4 2059 if (!CMM_LOAD_SHARED(ht->resize_initiated)) {
ed35e6d8 2060 if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
59290e9d 2061 return;
ed35e6d8 2062 }
f9830efd 2063 work = malloc(sizeof(*work));
741f378e
MD
2064 if (work == NULL) {
2065 dbg_printf("error allocating resize work, bailing out\n");
741f378e
MD
2066 return;
2067 }
f9830efd 2068 work->ht = ht;
d0ec0ed2
MD
2069 urcu_workqueue_queue_work(cds_lfht_workqueue,
2070 &work->work, do_resize_cb);
7b3893e4 2071 CMM_STORE_SHARED(ht->resize_initiated, 1);
f9830efd 2072 }
ab7d5fc6 2073}
3171717f 2074
f1f119ee
LJ
2075static
2076void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
2077{
2078 unsigned long target_size = size << growth;
2079
747d725c 2080 target_size = min(target_size, ht->max_nr_buckets);
f1f119ee
LJ
2081 if (resize_target_grow(ht, target_size) >= target_size)
2082 return;
2083
2084 __cds_lfht_resize_lazy_launch(ht);
2085}
2086
89bb121d
LJ
2087/*
2088 * We favor grow operations over shrink. A shrink operation never occurs
2089 * if a grow operation is queued for lazy execution. A grow operation
2090 * cancels any pending shrink lazy execution.
2091 */
3171717f 2092static
4105056a 2093void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
3171717f
MD
2094 unsigned long count)
2095{
b8af5011
MD
2096 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
2097 return;
d0d8f9aa 2098 count = max(count, MIN_TABLE_SIZE);
747d725c 2099 count = min(count, ht->max_nr_buckets);
89bb121d
LJ
2100 if (count == size)
2101 return; /* Already the right size, no resize needed */
2102 if (count > size) { /* lazy grow */
2103 if (resize_target_grow(ht, count) >= count)
2104 return;
2105 } else { /* lazy shrink */
2106 for (;;) {
2107 unsigned long s;
2108
7b3893e4 2109 s = uatomic_cmpxchg(&ht->resize_target, size, count);
89bb121d
LJ
2110 if (s == size)
2111 break; /* no resize needed */
2112 if (s > size)
2113 return; /* growing is/(was just) in progress */
2114 if (s <= count)
2115 return; /* some other thread do shrink */
2116 size = s;
2117 }
2118 }
f1f119ee 2119 __cds_lfht_resize_lazy_launch(ht);
3171717f 2120}
d0ec0ed2 2121
70469b43 2122static void cds_lfht_before_fork(void *priv __attribute__((unused)))
d0ec0ed2
MD
2123{
2124 if (cds_lfht_workqueue_atfork_nesting++)
2125 return;
2126 mutex_lock(&cds_lfht_fork_mutex);
2127 if (!cds_lfht_workqueue)
2128 return;
2129 urcu_workqueue_pause_worker(cds_lfht_workqueue);
2130}
2131
70469b43 2132static void cds_lfht_after_fork_parent(void *priv __attribute__((unused)))
d0ec0ed2
MD
2133{
2134 if (--cds_lfht_workqueue_atfork_nesting)
2135 return;
2136 if (!cds_lfht_workqueue)
2137 goto end;
2138 urcu_workqueue_resume_worker(cds_lfht_workqueue);
2139end:
2140 mutex_unlock(&cds_lfht_fork_mutex);
2141}
2142
70469b43 2143static void cds_lfht_after_fork_child(void *priv __attribute__((unused)))
d0ec0ed2
MD
2144{
2145 if (--cds_lfht_workqueue_atfork_nesting)
2146 return;
2147 if (!cds_lfht_workqueue)
2148 goto end;
2149 urcu_workqueue_create_worker(cds_lfht_workqueue);
2150end:
2151 mutex_unlock(&cds_lfht_fork_mutex);
2152}
2153
2154static struct urcu_atfork cds_lfht_atfork = {
2155 .before_fork = cds_lfht_before_fork,
2156 .after_fork_parent = cds_lfht_after_fork_parent,
2157 .after_fork_child = cds_lfht_after_fork_child,
2158};
2159
1a990de3 2160/*
2161 * Block all signals for the workqueue worker thread to ensure we don't
2162 * disturb the application. The SIGRCU signal needs to be unblocked for
2163 * the urcu-signal flavor.
2164 */
70469b43
MJ
2165static void cds_lfht_worker_init(
2166 struct urcu_workqueue *workqueue __attribute__((unused)),
2167 void *priv __attribute__((unused)))
d0ec0ed2
MD
2168{
2169 int ret;
2170 sigset_t mask;
2171
d0ec0ed2
MD
2172 ret = sigfillset(&mask);
2173 if (ret)
2174 urcu_die(errno);
1a990de3 2175 ret = sigdelset(&mask, SIGRCU);
2176 if (ret)
9fd30396 2177 urcu_die(errno);
1a990de3 2178 ret = pthread_sigmask(SIG_SETMASK, &mask, NULL);
d0ec0ed2
MD
2179 if (ret)
2180 urcu_die(ret);
2181}
2182
2183static void cds_lfht_init_worker(const struct rcu_flavor_struct *flavor)
2184{
2185 flavor->register_rculfhash_atfork(&cds_lfht_atfork);
2186
2187 mutex_lock(&cds_lfht_fork_mutex);
2188 if (cds_lfht_workqueue_user_count++)
2189 goto end;
2190 cds_lfht_workqueue = urcu_workqueue_create(0, -1, NULL,
2191 NULL, cds_lfht_worker_init, NULL, NULL, NULL, NULL, NULL);
2192end:
2193 mutex_unlock(&cds_lfht_fork_mutex);
2194}
2195
2196static void cds_lfht_fini_worker(const struct rcu_flavor_struct *flavor)
2197{
2198 mutex_lock(&cds_lfht_fork_mutex);
2199 if (--cds_lfht_workqueue_user_count)
2200 goto end;
2201 urcu_workqueue_destroy(cds_lfht_workqueue);
2202 cds_lfht_workqueue = NULL;
2203end:
2204 mutex_unlock(&cds_lfht_fork_mutex);
2205
2206 flavor->unregister_rculfhash_atfork(&cds_lfht_atfork);
2207}
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