d7a1f23bf8f766040341acbd18584246b5c327e4
[urcu.git] / src / rculfhash.c
1 /*
2 * rculfhash.c
3 *
4 * Userspace RCU library - Lock-Free Resizable RCU Hash Table
5 *
6 * Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
7 * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
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
22 */
23
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 *
33 * Some specificities of this Lock-Free Resizable RCU Hash Table
34 * implementation:
35 *
36 * - RCU read-side critical section allows readers to perform hash
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.
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
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.
50 * - Hash table nodes are contained within a split-ordered list. This
51 * list is ordered by incrementing reversed-bits-hash value.
52 * - An index of bucket nodes is kept. These bucket nodes are the hash
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.
62 * - The resize operation for larger tables (and available through an
63 * API) allows both expanding and shrinking the hash table.
64 * - Split-counters are used to keep track of the number of
65 * nodes within the hash table for automatic resize triggering.
66 * - Resize operation initiated by long chain detection is executed by a
67 * call_rcu thread, which keeps lock-freedom of add and remove.
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
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
89 * linked-list (the start node is never removed) and that it does not
90 * contain the "removed" node anymore, even if concurrent delete/add
91 * operations are changing the structure of the list concurrently.
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
95 * helping the remover unlink nodes from the list rather than to wait
96 * for it do to so.
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.
113 * - synchronize_rcu is used to garbage-collect the old bucket node table.
114 *
115 * Ordering Guarantees:
116 *
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
120 * cds_lfht_add_unique (failure).
121 *
122 * We define "read traversal" operation as any of the following
123 * group of operations
124 * - cds_lfht_lookup followed by iteration with cds_lfht_next_duplicate
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).
131 *
132 * We define "write" operations as any of cds_lfht_add, cds_lfht_replace,
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.
206 *
207 * Bucket node tables:
208 *
209 * hash table hash table the last all bucket node tables
210 * order size bucket node 0 1 2 3 4 5 6(index)
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 *
220 * When growing/shrinking, we only focus on the last bucket node table
221 * which size is (!order ? 1 : (1 << (order -1))).
222 *
223 * Example for growing/shrinking:
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
226 *
227 * A bit of ascii art explanation:
228 *
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.
231 *
232 * This shows the nodes for a small table ordered by reversed bits:
233 *
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
243 *
244 * This shows the nodes in order of non-reversed bits, linked by
245 * reversed-bit order.
246 *
247 * order bits reverse
248 * 0 0 000 000
249 * 1 | 1 001 100 <-
250 * 2 | | 2 010 010 <- |
251 * | | | 3 011 110 | <- |
252 * 3 -> | | | 4 100 001 | |
253 * -> | | 5 101 101 |
254 * -> | 6 110 011
255 * -> 7 111 111
256 */
257
258 #define _LGPL_SOURCE
259 #include <stdlib.h>
260 #include <errno.h>
261 #include <assert.h>
262 #include <stdio.h>
263 #include <stdint.h>
264 #include <string.h>
265 #include <sched.h>
266 #include <unistd.h>
267
268 #include "compat-getcpu.h"
269 #include <urcu-pointer.h>
270 #include <urcu-call-rcu.h>
271 #include <urcu-flavor.h>
272 #include <urcu/arch.h>
273 #include <urcu/uatomic.h>
274 #include <urcu/compiler.h>
275 #include <urcu/rculfhash.h>
276 #include <rculfhash-internal.h>
277 #include <stdio.h>
278 #include <pthread.h>
279
280 /*
281 * Split-counters lazily update the global counter each 1024
282 * addition/removal. It automatically keeps track of resize required.
283 * We use the bucket length as indicator for need to expand for small
284 * tables and machines lacking per-cpu data support.
285 */
286 #define COUNT_COMMIT_ORDER 10
287 #define DEFAULT_SPLIT_COUNT_MASK 0xFUL
288 #define CHAIN_LEN_TARGET 1
289 #define CHAIN_LEN_RESIZE_THRESHOLD 3
290
291 /*
292 * Define the minimum table size.
293 */
294 #define MIN_TABLE_ORDER 0
295 #define MIN_TABLE_SIZE (1UL << MIN_TABLE_ORDER)
296
297 /*
298 * Minimum number of bucket nodes to touch per thread to parallelize grow/shrink.
299 */
300 #define MIN_PARTITION_PER_THREAD_ORDER 12
301 #define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
302
303 /*
304 * The removed flag needs to be updated atomically with the pointer.
305 * It indicates that no node must attach to the node scheduled for
306 * removal, and that node garbage collection must be performed.
307 * The bucket flag does not require to be updated atomically with the
308 * pointer, but it is added as a pointer low bit flag to save space.
309 * The "removal owner" flag is used to detect which of the "del"
310 * operation that has set the "removed flag" gets to return the removed
311 * node to its caller. Note that the replace operation does not need to
312 * iteract with the "removal owner" flag, because it validates that
313 * the "removed" flag is not set before performing its cmpxchg.
314 */
315 #define REMOVED_FLAG (1UL << 0)
316 #define BUCKET_FLAG (1UL << 1)
317 #define REMOVAL_OWNER_FLAG (1UL << 2)
318 #define FLAGS_MASK ((1UL << 3) - 1)
319
320 /* Value of the end pointer. Should not interact with flags. */
321 #define END_VALUE NULL
322
323 /*
324 * ht_items_count: Split-counters counting the number of node addition
325 * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
326 * is set at hash table creation.
327 *
328 * These are free-running counters, never reset to zero. They count the
329 * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
330 * operations to update the global counter. We choose a power-of-2 value
331 * for the trigger to deal with 32 or 64-bit overflow of the counter.
332 */
333 struct ht_items_count {
334 unsigned long add, del;
335 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
336
337 /*
338 * rcu_resize_work: Contains arguments passed to RCU worker thread
339 * responsible for performing lazy resize.
340 */
341 struct rcu_resize_work {
342 struct rcu_head head;
343 struct cds_lfht *ht;
344 };
345
346 /*
347 * partition_resize_work: Contains arguments passed to worker threads
348 * executing the hash table resize on partitions of the hash table
349 * assigned to each processor's worker thread.
350 */
351 struct partition_resize_work {
352 pthread_t thread_id;
353 struct cds_lfht *ht;
354 unsigned long i, start, len;
355 void (*fct)(struct cds_lfht *ht, unsigned long i,
356 unsigned long start, unsigned long len);
357 };
358
359 /*
360 * Algorithm to reverse bits in a word by lookup table, extended to
361 * 64-bit words.
362 * Source:
363 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
364 * Originally from Public Domain.
365 */
366
367 static const uint8_t BitReverseTable256[256] =
368 {
369 #define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
370 #define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
371 #define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
372 R6(0), R6(2), R6(1), R6(3)
373 };
374 #undef R2
375 #undef R4
376 #undef R6
377
378 static
379 uint8_t bit_reverse_u8(uint8_t v)
380 {
381 return BitReverseTable256[v];
382 }
383
384 #if (CAA_BITS_PER_LONG == 32)
385 static
386 uint32_t bit_reverse_u32(uint32_t v)
387 {
388 return ((uint32_t) bit_reverse_u8(v) << 24) |
389 ((uint32_t) bit_reverse_u8(v >> 8) << 16) |
390 ((uint32_t) bit_reverse_u8(v >> 16) << 8) |
391 ((uint32_t) bit_reverse_u8(v >> 24));
392 }
393 #else
394 static
395 uint64_t bit_reverse_u64(uint64_t v)
396 {
397 return ((uint64_t) bit_reverse_u8(v) << 56) |
398 ((uint64_t) bit_reverse_u8(v >> 8) << 48) |
399 ((uint64_t) bit_reverse_u8(v >> 16) << 40) |
400 ((uint64_t) bit_reverse_u8(v >> 24) << 32) |
401 ((uint64_t) bit_reverse_u8(v >> 32) << 24) |
402 ((uint64_t) bit_reverse_u8(v >> 40) << 16) |
403 ((uint64_t) bit_reverse_u8(v >> 48) << 8) |
404 ((uint64_t) bit_reverse_u8(v >> 56));
405 }
406 #endif
407
408 static
409 unsigned long bit_reverse_ulong(unsigned long v)
410 {
411 #if (CAA_BITS_PER_LONG == 32)
412 return bit_reverse_u32(v);
413 #else
414 return bit_reverse_u64(v);
415 #endif
416 }
417
418 /*
419 * fls: returns the position of the most significant bit.
420 * Returns 0 if no bit is set, else returns the position of the most
421 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
422 */
423 #if defined(__i386) || defined(__x86_64)
424 static inline
425 unsigned int fls_u32(uint32_t x)
426 {
427 int r;
428
429 __asm__ ("bsrl %1,%0\n\t"
430 "jnz 1f\n\t"
431 "movl $-1,%0\n\t"
432 "1:\n\t"
433 : "=r" (r) : "rm" (x));
434 return r + 1;
435 }
436 #define HAS_FLS_U32
437 #endif
438
439 #if defined(__x86_64)
440 static inline
441 unsigned int fls_u64(uint64_t x)
442 {
443 long r;
444
445 __asm__ ("bsrq %1,%0\n\t"
446 "jnz 1f\n\t"
447 "movq $-1,%0\n\t"
448 "1:\n\t"
449 : "=r" (r) : "rm" (x));
450 return r + 1;
451 }
452 #define HAS_FLS_U64
453 #endif
454
455 #ifndef HAS_FLS_U64
456 static __attribute__((unused))
457 unsigned int fls_u64(uint64_t x)
458 {
459 unsigned int r = 64;
460
461 if (!x)
462 return 0;
463
464 if (!(x & 0xFFFFFFFF00000000ULL)) {
465 x <<= 32;
466 r -= 32;
467 }
468 if (!(x & 0xFFFF000000000000ULL)) {
469 x <<= 16;
470 r -= 16;
471 }
472 if (!(x & 0xFF00000000000000ULL)) {
473 x <<= 8;
474 r -= 8;
475 }
476 if (!(x & 0xF000000000000000ULL)) {
477 x <<= 4;
478 r -= 4;
479 }
480 if (!(x & 0xC000000000000000ULL)) {
481 x <<= 2;
482 r -= 2;
483 }
484 if (!(x & 0x8000000000000000ULL)) {
485 x <<= 1;
486 r -= 1;
487 }
488 return r;
489 }
490 #endif
491
492 #ifndef HAS_FLS_U32
493 static __attribute__((unused))
494 unsigned int fls_u32(uint32_t x)
495 {
496 unsigned int r = 32;
497
498 if (!x)
499 return 0;
500 if (!(x & 0xFFFF0000U)) {
501 x <<= 16;
502 r -= 16;
503 }
504 if (!(x & 0xFF000000U)) {
505 x <<= 8;
506 r -= 8;
507 }
508 if (!(x & 0xF0000000U)) {
509 x <<= 4;
510 r -= 4;
511 }
512 if (!(x & 0xC0000000U)) {
513 x <<= 2;
514 r -= 2;
515 }
516 if (!(x & 0x80000000U)) {
517 x <<= 1;
518 r -= 1;
519 }
520 return r;
521 }
522 #endif
523
524 unsigned int cds_lfht_fls_ulong(unsigned long x)
525 {
526 #if (CAA_BITS_PER_LONG == 32)
527 return fls_u32(x);
528 #else
529 return fls_u64(x);
530 #endif
531 }
532
533 /*
534 * Return the minimum order for which x <= (1UL << order).
535 * Return -1 if x is 0.
536 */
537 int cds_lfht_get_count_order_u32(uint32_t x)
538 {
539 if (!x)
540 return -1;
541
542 return fls_u32(x - 1);
543 }
544
545 /*
546 * Return the minimum order for which x <= (1UL << order).
547 * Return -1 if x is 0.
548 */
549 int cds_lfht_get_count_order_ulong(unsigned long x)
550 {
551 if (!x)
552 return -1;
553
554 return cds_lfht_fls_ulong(x - 1);
555 }
556
557 static
558 void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth);
559
560 static
561 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
562 unsigned long count);
563
564 static long nr_cpus_mask = -1;
565 static long split_count_mask = -1;
566 static int split_count_order = -1;
567
568 #if defined(HAVE_SYSCONF)
569 static void ht_init_nr_cpus_mask(void)
570 {
571 long maxcpus;
572
573 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
574 if (maxcpus <= 0) {
575 nr_cpus_mask = -2;
576 return;
577 }
578 /*
579 * round up number of CPUs to next power of two, so we
580 * can use & for modulo.
581 */
582 maxcpus = 1UL << cds_lfht_get_count_order_ulong(maxcpus);
583 nr_cpus_mask = maxcpus - 1;
584 }
585 #else /* #if defined(HAVE_SYSCONF) */
586 static void ht_init_nr_cpus_mask(void)
587 {
588 nr_cpus_mask = -2;
589 }
590 #endif /* #else #if defined(HAVE_SYSCONF) */
591
592 static
593 void alloc_split_items_count(struct cds_lfht *ht)
594 {
595 if (nr_cpus_mask == -1) {
596 ht_init_nr_cpus_mask();
597 if (nr_cpus_mask < 0)
598 split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
599 else
600 split_count_mask = nr_cpus_mask;
601 split_count_order =
602 cds_lfht_get_count_order_ulong(split_count_mask + 1);
603 }
604
605 assert(split_count_mask >= 0);
606
607 if (ht->flags & CDS_LFHT_ACCOUNTING) {
608 ht->split_count = calloc(split_count_mask + 1,
609 sizeof(struct ht_items_count));
610 assert(ht->split_count);
611 } else {
612 ht->split_count = NULL;
613 }
614 }
615
616 static
617 void free_split_items_count(struct cds_lfht *ht)
618 {
619 poison_free(ht->split_count);
620 }
621
622 static
623 int ht_get_split_count_index(unsigned long hash)
624 {
625 int cpu;
626
627 assert(split_count_mask >= 0);
628 cpu = urcu_sched_getcpu();
629 if (caa_unlikely(cpu < 0))
630 return hash & split_count_mask;
631 else
632 return cpu & split_count_mask;
633 }
634
635 static
636 void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash)
637 {
638 unsigned long split_count;
639 int index;
640 long count;
641
642 if (caa_unlikely(!ht->split_count))
643 return;
644 index = ht_get_split_count_index(hash);
645 split_count = uatomic_add_return(&ht->split_count[index].add, 1);
646 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
647 return;
648 /* Only if number of add multiple of 1UL << COUNT_COMMIT_ORDER */
649
650 dbg_printf("add split count %lu\n", split_count);
651 count = uatomic_add_return(&ht->count,
652 1UL << COUNT_COMMIT_ORDER);
653 if (caa_likely(count & (count - 1)))
654 return;
655 /* Only if global count is power of 2 */
656
657 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) < size)
658 return;
659 dbg_printf("add set global %ld\n", count);
660 cds_lfht_resize_lazy_count(ht, size,
661 count >> (CHAIN_LEN_TARGET - 1));
662 }
663
664 static
665 void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
666 {
667 unsigned long split_count;
668 int index;
669 long count;
670
671 if (caa_unlikely(!ht->split_count))
672 return;
673 index = ht_get_split_count_index(hash);
674 split_count = uatomic_add_return(&ht->split_count[index].del, 1);
675 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
676 return;
677 /* Only if number of deletes multiple of 1UL << COUNT_COMMIT_ORDER */
678
679 dbg_printf("del split count %lu\n", split_count);
680 count = uatomic_add_return(&ht->count,
681 -(1UL << COUNT_COMMIT_ORDER));
682 if (caa_likely(count & (count - 1)))
683 return;
684 /* Only if global count is power of 2 */
685
686 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) >= size)
687 return;
688 dbg_printf("del set global %ld\n", count);
689 /*
690 * Don't shrink table if the number of nodes is below a
691 * certain threshold.
692 */
693 if (count < (1UL << COUNT_COMMIT_ORDER) * (split_count_mask + 1))
694 return;
695 cds_lfht_resize_lazy_count(ht, size,
696 count >> (CHAIN_LEN_TARGET - 1));
697 }
698
699 static
700 void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
701 {
702 unsigned long count;
703
704 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
705 return;
706 count = uatomic_read(&ht->count);
707 /*
708 * Use bucket-local length for small table expand and for
709 * environments lacking per-cpu data support.
710 */
711 if (count >= (1UL << (COUNT_COMMIT_ORDER + split_count_order)))
712 return;
713 if (chain_len > 100)
714 dbg_printf("WARNING: large chain length: %u.\n",
715 chain_len);
716 if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD) {
717 int growth;
718
719 /*
720 * Ideal growth calculated based on chain length.
721 */
722 growth = cds_lfht_get_count_order_u32(chain_len
723 - (CHAIN_LEN_TARGET - 1));
724 if ((ht->flags & CDS_LFHT_ACCOUNTING)
725 && (size << growth)
726 >= (1UL << (COUNT_COMMIT_ORDER
727 + split_count_order))) {
728 /*
729 * If ideal growth expands the hash table size
730 * beyond the "small hash table" sizes, use the
731 * maximum small hash table size to attempt
732 * expanding the hash table. This only applies
733 * when node accounting is available, otherwise
734 * the chain length is used to expand the hash
735 * table in every case.
736 */
737 growth = COUNT_COMMIT_ORDER + split_count_order
738 - cds_lfht_get_count_order_ulong(size);
739 if (growth <= 0)
740 return;
741 }
742 cds_lfht_resize_lazy_grow(ht, size, growth);
743 }
744 }
745
746 static
747 struct cds_lfht_node *clear_flag(struct cds_lfht_node *node)
748 {
749 return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK);
750 }
751
752 static
753 int is_removed(struct cds_lfht_node *node)
754 {
755 return ((unsigned long) node) & REMOVED_FLAG;
756 }
757
758 static
759 int is_bucket(struct cds_lfht_node *node)
760 {
761 return ((unsigned long) node) & BUCKET_FLAG;
762 }
763
764 static
765 struct cds_lfht_node *flag_bucket(struct cds_lfht_node *node)
766 {
767 return (struct cds_lfht_node *) (((unsigned long) node) | BUCKET_FLAG);
768 }
769
770 static
771 int is_removal_owner(struct cds_lfht_node *node)
772 {
773 return ((unsigned long) node) & REMOVAL_OWNER_FLAG;
774 }
775
776 static
777 struct cds_lfht_node *flag_removal_owner(struct cds_lfht_node *node)
778 {
779 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVAL_OWNER_FLAG);
780 }
781
782 static
783 struct cds_lfht_node *flag_removed_or_removal_owner(struct cds_lfht_node *node)
784 {
785 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG | REMOVAL_OWNER_FLAG);
786 }
787
788 static
789 struct cds_lfht_node *get_end(void)
790 {
791 return (struct cds_lfht_node *) END_VALUE;
792 }
793
794 static
795 int is_end(struct cds_lfht_node *node)
796 {
797 return clear_flag(node) == (struct cds_lfht_node *) END_VALUE;
798 }
799
800 static
801 unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr,
802 unsigned long v)
803 {
804 unsigned long old1, old2;
805
806 old1 = uatomic_read(ptr);
807 do {
808 old2 = old1;
809 if (old2 >= v)
810 return old2;
811 } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
812 return old2;
813 }
814
815 static
816 void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
817 {
818 return ht->mm->alloc_bucket_table(ht, order);
819 }
820
821 /*
822 * cds_lfht_free_bucket_table() should be called with decreasing order.
823 * When cds_lfht_free_bucket_table(0) is called, it means the whole
824 * lfht is destroyed.
825 */
826 static
827 void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order)
828 {
829 return ht->mm->free_bucket_table(ht, order);
830 }
831
832 static inline
833 struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
834 {
835 return ht->bucket_at(ht, index);
836 }
837
838 static inline
839 struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
840 unsigned long hash)
841 {
842 assert(size > 0);
843 return bucket_at(ht, hash & (size - 1));
844 }
845
846 /*
847 * Remove all logically deleted nodes from a bucket up to a certain node key.
848 */
849 static
850 void _cds_lfht_gc_bucket(struct cds_lfht_node *bucket, struct cds_lfht_node *node)
851 {
852 struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
853
854 assert(!is_bucket(bucket));
855 assert(!is_removed(bucket));
856 assert(!is_removal_owner(bucket));
857 assert(!is_bucket(node));
858 assert(!is_removed(node));
859 assert(!is_removal_owner(node));
860 for (;;) {
861 iter_prev = bucket;
862 /* We can always skip the bucket node initially */
863 iter = rcu_dereference(iter_prev->next);
864 assert(!is_removed(iter));
865 assert(!is_removal_owner(iter));
866 assert(iter_prev->reverse_hash <= node->reverse_hash);
867 /*
868 * We should never be called with bucket (start of chain)
869 * and logically removed node (end of path compression
870 * marker) being the actual same node. This would be a
871 * bug in the algorithm implementation.
872 */
873 assert(bucket != node);
874 for (;;) {
875 if (caa_unlikely(is_end(iter)))
876 return;
877 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
878 return;
879 next = rcu_dereference(clear_flag(iter)->next);
880 if (caa_likely(is_removed(next)))
881 break;
882 iter_prev = clear_flag(iter);
883 iter = next;
884 }
885 assert(!is_removed(iter));
886 assert(!is_removal_owner(iter));
887 if (is_bucket(iter))
888 new_next = flag_bucket(clear_flag(next));
889 else
890 new_next = clear_flag(next);
891 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
892 }
893 }
894
895 static
896 int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
897 struct cds_lfht_node *old_node,
898 struct cds_lfht_node *old_next,
899 struct cds_lfht_node *new_node)
900 {
901 struct cds_lfht_node *bucket, *ret_next;
902
903 if (!old_node) /* Return -ENOENT if asked to replace NULL node */
904 return -ENOENT;
905
906 assert(!is_removed(old_node));
907 assert(!is_removal_owner(old_node));
908 assert(!is_bucket(old_node));
909 assert(!is_removed(new_node));
910 assert(!is_removal_owner(new_node));
911 assert(!is_bucket(new_node));
912 assert(new_node != old_node);
913 for (;;) {
914 /* Insert after node to be replaced */
915 if (is_removed(old_next)) {
916 /*
917 * Too late, the old node has been removed under us
918 * between lookup and replace. Fail.
919 */
920 return -ENOENT;
921 }
922 assert(old_next == clear_flag(old_next));
923 assert(new_node != old_next);
924 /*
925 * REMOVAL_OWNER flag is _NEVER_ set before the REMOVED
926 * flag. It is either set atomically at the same time
927 * (replace) or after (del).
928 */
929 assert(!is_removal_owner(old_next));
930 new_node->next = old_next;
931 /*
932 * Here is the whole trick for lock-free replace: we add
933 * the replacement node _after_ the node we want to
934 * replace by atomically setting its next pointer at the
935 * same time we set its removal flag. Given that
936 * the lookups/get next use an iterator aware of the
937 * next pointer, they will either skip the old node due
938 * to the removal flag and see the new node, or use
939 * the old node, but will not see the new one.
940 * This is a replacement of a node with another node
941 * that has the same value: we are therefore not
942 * removing a value from the hash table. We set both the
943 * REMOVED and REMOVAL_OWNER flags atomically so we own
944 * the node after successful cmpxchg.
945 */
946 ret_next = uatomic_cmpxchg(&old_node->next,
947 old_next, flag_removed_or_removal_owner(new_node));
948 if (ret_next == old_next)
949 break; /* We performed the replacement. */
950 old_next = ret_next;
951 }
952
953 /*
954 * Ensure that the old node is not visible to readers anymore:
955 * lookup for the node, and remove it (along with any other
956 * logically removed node) if found.
957 */
958 bucket = lookup_bucket(ht, size, bit_reverse_ulong(old_node->reverse_hash));
959 _cds_lfht_gc_bucket(bucket, new_node);
960
961 assert(is_removed(CMM_LOAD_SHARED(old_node->next)));
962 return 0;
963 }
964
965 /*
966 * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
967 * mode. A NULL unique_ret allows creation of duplicate keys.
968 */
969 static
970 void _cds_lfht_add(struct cds_lfht *ht,
971 unsigned long hash,
972 cds_lfht_match_fct match,
973 const void *key,
974 unsigned long size,
975 struct cds_lfht_node *node,
976 struct cds_lfht_iter *unique_ret,
977 int bucket_flag)
978 {
979 struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
980 *return_node;
981 struct cds_lfht_node *bucket;
982
983 assert(!is_bucket(node));
984 assert(!is_removed(node));
985 assert(!is_removal_owner(node));
986 bucket = lookup_bucket(ht, size, hash);
987 for (;;) {
988 uint32_t chain_len = 0;
989
990 /*
991 * iter_prev points to the non-removed node prior to the
992 * insert location.
993 */
994 iter_prev = bucket;
995 /* We can always skip the bucket node initially */
996 iter = rcu_dereference(iter_prev->next);
997 assert(iter_prev->reverse_hash <= node->reverse_hash);
998 for (;;) {
999 if (caa_unlikely(is_end(iter)))
1000 goto insert;
1001 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
1002 goto insert;
1003
1004 /* bucket node is the first node of the identical-hash-value chain */
1005 if (bucket_flag && clear_flag(iter)->reverse_hash == node->reverse_hash)
1006 goto insert;
1007
1008 next = rcu_dereference(clear_flag(iter)->next);
1009 if (caa_unlikely(is_removed(next)))
1010 goto gc_node;
1011
1012 /* uniquely add */
1013 if (unique_ret
1014 && !is_bucket(next)
1015 && clear_flag(iter)->reverse_hash == node->reverse_hash) {
1016 struct cds_lfht_iter d_iter = { .node = node, .next = iter, };
1017
1018 /*
1019 * uniquely adding inserts the node as the first
1020 * node of the identical-hash-value node chain.
1021 *
1022 * This semantic ensures no duplicated keys
1023 * should ever be observable in the table
1024 * (including traversing the table node by
1025 * node by forward iterations)
1026 */
1027 cds_lfht_next_duplicate(ht, match, key, &d_iter);
1028 if (!d_iter.node)
1029 goto insert;
1030
1031 *unique_ret = d_iter;
1032 return;
1033 }
1034
1035 /* Only account for identical reverse hash once */
1036 if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash
1037 && !is_bucket(next))
1038 check_resize(ht, size, ++chain_len);
1039 iter_prev = clear_flag(iter);
1040 iter = next;
1041 }
1042
1043 insert:
1044 assert(node != clear_flag(iter));
1045 assert(!is_removed(iter_prev));
1046 assert(!is_removal_owner(iter_prev));
1047 assert(!is_removed(iter));
1048 assert(!is_removal_owner(iter));
1049 assert(iter_prev != node);
1050 if (!bucket_flag)
1051 node->next = clear_flag(iter);
1052 else
1053 node->next = flag_bucket(clear_flag(iter));
1054 if (is_bucket(iter))
1055 new_node = flag_bucket(node);
1056 else
1057 new_node = node;
1058 if (uatomic_cmpxchg(&iter_prev->next, iter,
1059 new_node) != iter) {
1060 continue; /* retry */
1061 } else {
1062 return_node = node;
1063 goto end;
1064 }
1065
1066 gc_node:
1067 assert(!is_removed(iter));
1068 assert(!is_removal_owner(iter));
1069 if (is_bucket(iter))
1070 new_next = flag_bucket(clear_flag(next));
1071 else
1072 new_next = clear_flag(next);
1073 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
1074 /* retry */
1075 }
1076 end:
1077 if (unique_ret) {
1078 unique_ret->node = return_node;
1079 /* unique_ret->next left unset, never used. */
1080 }
1081 }
1082
1083 static
1084 int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
1085 struct cds_lfht_node *node)
1086 {
1087 struct cds_lfht_node *bucket, *next;
1088
1089 if (!node) /* Return -ENOENT if asked to delete NULL node */
1090 return -ENOENT;
1091
1092 /* logically delete the node */
1093 assert(!is_bucket(node));
1094 assert(!is_removed(node));
1095 assert(!is_removal_owner(node));
1096
1097 /*
1098 * We are first checking if the node had previously been
1099 * logically removed (this check is not atomic with setting the
1100 * logical removal flag). Return -ENOENT if the node had
1101 * previously been removed.
1102 */
1103 next = CMM_LOAD_SHARED(node->next); /* next is not dereferenced */
1104 if (caa_unlikely(is_removed(next)))
1105 return -ENOENT;
1106 assert(!is_bucket(next));
1107 /*
1108 * The del operation semantic guarantees a full memory barrier
1109 * before the uatomic_or atomic commit of the deletion flag.
1110 */
1111 cmm_smp_mb__before_uatomic_or();
1112 /*
1113 * We set the REMOVED_FLAG unconditionally. Note that there may
1114 * be more than one concurrent thread setting this flag.
1115 * Knowing which wins the race will be known after the garbage
1116 * collection phase, stay tuned!
1117 */
1118 uatomic_or(&node->next, REMOVED_FLAG);
1119 /* We performed the (logical) deletion. */
1120
1121 /*
1122 * Ensure that the node is not visible to readers anymore: lookup for
1123 * the node, and remove it (along with any other logically removed node)
1124 * if found.
1125 */
1126 bucket = lookup_bucket(ht, size, bit_reverse_ulong(node->reverse_hash));
1127 _cds_lfht_gc_bucket(bucket, node);
1128
1129 assert(is_removed(CMM_LOAD_SHARED(node->next)));
1130 /*
1131 * Last phase: atomically exchange node->next with a version
1132 * having "REMOVAL_OWNER_FLAG" set. If the returned node->next
1133 * pointer did _not_ have "REMOVAL_OWNER_FLAG" set, we now own
1134 * the node and win the removal race.
1135 * It is interesting to note that all "add" paths are forbidden
1136 * to change the next pointer starting from the point where the
1137 * REMOVED_FLAG is set, so here using a read, followed by a
1138 * xchg() suffice to guarantee that the xchg() will ever only
1139 * set the "REMOVAL_OWNER_FLAG" (or change nothing if the flag
1140 * was already set).
1141 */
1142 if (!is_removal_owner(uatomic_xchg(&node->next,
1143 flag_removal_owner(node->next))))
1144 return 0;
1145 else
1146 return -ENOENT;
1147 }
1148
1149 static
1150 void *partition_resize_thread(void *arg)
1151 {
1152 struct partition_resize_work *work = arg;
1153
1154 work->ht->flavor->register_thread();
1155 work->fct(work->ht, work->i, work->start, work->len);
1156 work->ht->flavor->unregister_thread();
1157 return NULL;
1158 }
1159
1160 static
1161 void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
1162 unsigned long len,
1163 void (*fct)(struct cds_lfht *ht, unsigned long i,
1164 unsigned long start, unsigned long len))
1165 {
1166 unsigned long partition_len, start = 0;
1167 struct partition_resize_work *work;
1168 int thread, ret;
1169 unsigned long nr_threads;
1170
1171 assert(nr_cpus_mask != -1);
1172 if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD)
1173 goto fallback;
1174
1175 /*
1176 * Note: nr_cpus_mask + 1 is always power of 2.
1177 * We spawn just the number of threads we need to satisfy the minimum
1178 * partition size, up to the number of CPUs in the system.
1179 */
1180 if (nr_cpus_mask > 0) {
1181 nr_threads = min(nr_cpus_mask + 1,
1182 len >> MIN_PARTITION_PER_THREAD_ORDER);
1183 } else {
1184 nr_threads = 1;
1185 }
1186 partition_len = len >> cds_lfht_get_count_order_ulong(nr_threads);
1187 work = calloc(nr_threads, sizeof(*work));
1188 if (!work) {
1189 dbg_printf("error allocating for resize, single-threading\n");
1190 goto fallback;
1191 }
1192 for (thread = 0; thread < nr_threads; thread++) {
1193 work[thread].ht = ht;
1194 work[thread].i = i;
1195 work[thread].len = partition_len;
1196 work[thread].start = thread * partition_len;
1197 work[thread].fct = fct;
1198 ret = pthread_create(&(work[thread].thread_id), ht->resize_attr,
1199 partition_resize_thread, &work[thread]);
1200 if (ret == EAGAIN) {
1201 /*
1202 * Out of resources: wait and join the threads
1203 * we've created, then handle leftovers.
1204 */
1205 dbg_printf("error spawning for resize, single-threading\n");
1206 start = work[thread].start;
1207 len -= start;
1208 nr_threads = thread;
1209 break;
1210 }
1211 assert(!ret);
1212 }
1213 for (thread = 0; thread < nr_threads; thread++) {
1214 ret = pthread_join(work[thread].thread_id, NULL);
1215 assert(!ret);
1216 }
1217 free(work);
1218
1219 /*
1220 * A pthread_create failure above will either lead in us having
1221 * no threads to join or starting at a non-zero offset,
1222 * fallback to single thread processing of leftovers.
1223 */
1224 if (start == 0 && nr_threads > 0)
1225 return;
1226 fallback:
1227 ht->flavor->thread_online();
1228 fct(ht, i, start, len);
1229 ht->flavor->thread_offline();
1230 }
1231
1232 /*
1233 * Holding RCU read lock to protect _cds_lfht_add against memory
1234 * reclaim that could be performed by other call_rcu worker threads (ABA
1235 * problem).
1236 *
1237 * When we reach a certain length, we can split this population phase over
1238 * many worker threads, based on the number of CPUs available in the system.
1239 * This should therefore take care of not having the expand lagging behind too
1240 * many concurrent insertion threads by using the scheduler's ability to
1241 * schedule bucket node population fairly with insertions.
1242 */
1243 static
1244 void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
1245 unsigned long start, unsigned long len)
1246 {
1247 unsigned long j, size = 1UL << (i - 1);
1248
1249 assert(i > MIN_TABLE_ORDER);
1250 ht->flavor->read_lock();
1251 for (j = size + start; j < size + start + len; j++) {
1252 struct cds_lfht_node *new_node = bucket_at(ht, j);
1253
1254 assert(j >= size && j < (size << 1));
1255 dbg_printf("init populate: order %lu index %lu hash %lu\n",
1256 i, j, j);
1257 new_node->reverse_hash = bit_reverse_ulong(j);
1258 _cds_lfht_add(ht, j, NULL, NULL, size, new_node, NULL, 1);
1259 }
1260 ht->flavor->read_unlock();
1261 }
1262
1263 static
1264 void init_table_populate(struct cds_lfht *ht, unsigned long i,
1265 unsigned long len)
1266 {
1267 partition_resize_helper(ht, i, len, init_table_populate_partition);
1268 }
1269
1270 static
1271 void init_table(struct cds_lfht *ht,
1272 unsigned long first_order, unsigned long last_order)
1273 {
1274 unsigned long i;
1275
1276 dbg_printf("init table: first_order %lu last_order %lu\n",
1277 first_order, last_order);
1278 assert(first_order > MIN_TABLE_ORDER);
1279 for (i = first_order; i <= last_order; i++) {
1280 unsigned long len;
1281
1282 len = 1UL << (i - 1);
1283 dbg_printf("init order %lu len: %lu\n", i, len);
1284
1285 /* Stop expand if the resize target changes under us */
1286 if (CMM_LOAD_SHARED(ht->resize_target) < (1UL << i))
1287 break;
1288
1289 cds_lfht_alloc_bucket_table(ht, i);
1290
1291 /*
1292 * Set all bucket nodes reverse hash values for a level and
1293 * link all bucket nodes into the table.
1294 */
1295 init_table_populate(ht, i, len);
1296
1297 /*
1298 * Update table size.
1299 */
1300 cmm_smp_wmb(); /* populate data before RCU size */
1301 CMM_STORE_SHARED(ht->size, 1UL << i);
1302
1303 dbg_printf("init new size: %lu\n", 1UL << i);
1304 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1305 break;
1306 }
1307 }
1308
1309 /*
1310 * Holding RCU read lock to protect _cds_lfht_remove against memory
1311 * reclaim that could be performed by other call_rcu worker threads (ABA
1312 * problem).
1313 * For a single level, we logically remove and garbage collect each node.
1314 *
1315 * As a design choice, we perform logical removal and garbage collection on a
1316 * node-per-node basis to simplify this algorithm. We also assume keeping good
1317 * cache locality of the operation would overweight possible performance gain
1318 * that could be achieved by batching garbage collection for multiple levels.
1319 * However, this would have to be justified by benchmarks.
1320 *
1321 * Concurrent removal and add operations are helping us perform garbage
1322 * collection of logically removed nodes. We guarantee that all logically
1323 * removed nodes have been garbage-collected (unlinked) before call_rcu is
1324 * invoked to free a hole level of bucket nodes (after a grace period).
1325 *
1326 * Logical removal and garbage collection can therefore be done in batch
1327 * or on a node-per-node basis, as long as the guarantee above holds.
1328 *
1329 * When we reach a certain length, we can split this removal over many worker
1330 * threads, based on the number of CPUs available in the system. This should
1331 * take care of not letting resize process lag behind too many concurrent
1332 * updater threads actively inserting into the hash table.
1333 */
1334 static
1335 void remove_table_partition(struct cds_lfht *ht, unsigned long i,
1336 unsigned long start, unsigned long len)
1337 {
1338 unsigned long j, size = 1UL << (i - 1);
1339
1340 assert(i > MIN_TABLE_ORDER);
1341 ht->flavor->read_lock();
1342 for (j = size + start; j < size + start + len; j++) {
1343 struct cds_lfht_node *fini_bucket = bucket_at(ht, j);
1344 struct cds_lfht_node *parent_bucket = bucket_at(ht, j - size);
1345
1346 assert(j >= size && j < (size << 1));
1347 dbg_printf("remove entry: order %lu index %lu hash %lu\n",
1348 i, j, j);
1349 /* Set the REMOVED_FLAG to freeze the ->next for gc */
1350 uatomic_or(&fini_bucket->next, REMOVED_FLAG);
1351 _cds_lfht_gc_bucket(parent_bucket, fini_bucket);
1352 }
1353 ht->flavor->read_unlock();
1354 }
1355
1356 static
1357 void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
1358 {
1359 partition_resize_helper(ht, i, len, remove_table_partition);
1360 }
1361
1362 /*
1363 * fini_table() is never called for first_order == 0, which is why
1364 * free_by_rcu_order == 0 can be used as criterion to know if free must
1365 * be called.
1366 */
1367 static
1368 void fini_table(struct cds_lfht *ht,
1369 unsigned long first_order, unsigned long last_order)
1370 {
1371 long i;
1372 unsigned long free_by_rcu_order = 0;
1373
1374 dbg_printf("fini table: first_order %lu last_order %lu\n",
1375 first_order, last_order);
1376 assert(first_order > MIN_TABLE_ORDER);
1377 for (i = last_order; i >= first_order; i--) {
1378 unsigned long len;
1379
1380 len = 1UL << (i - 1);
1381 dbg_printf("fini order %ld len: %lu\n", i, len);
1382
1383 /* Stop shrink if the resize target changes under us */
1384 if (CMM_LOAD_SHARED(ht->resize_target) > (1UL << (i - 1)))
1385 break;
1386
1387 cmm_smp_wmb(); /* populate data before RCU size */
1388 CMM_STORE_SHARED(ht->size, 1UL << (i - 1));
1389
1390 /*
1391 * We need to wait for all add operations to reach Q.S. (and
1392 * thus use the new table for lookups) before we can start
1393 * releasing the old bucket nodes. Otherwise their lookup will
1394 * return a logically removed node as insert position.
1395 */
1396 ht->flavor->update_synchronize_rcu();
1397 if (free_by_rcu_order)
1398 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
1399
1400 /*
1401 * Set "removed" flag in bucket nodes about to be removed.
1402 * Unlink all now-logically-removed bucket node pointers.
1403 * Concurrent add/remove operation are helping us doing
1404 * the gc.
1405 */
1406 remove_table(ht, i, len);
1407
1408 free_by_rcu_order = i;
1409
1410 dbg_printf("fini new size: %lu\n", 1UL << i);
1411 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1412 break;
1413 }
1414
1415 if (free_by_rcu_order) {
1416 ht->flavor->update_synchronize_rcu();
1417 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
1418 }
1419 }
1420
1421 static
1422 void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size)
1423 {
1424 struct cds_lfht_node *prev, *node;
1425 unsigned long order, len, i;
1426
1427 cds_lfht_alloc_bucket_table(ht, 0);
1428
1429 dbg_printf("create bucket: order 0 index 0 hash 0\n");
1430 node = bucket_at(ht, 0);
1431 node->next = flag_bucket(get_end());
1432 node->reverse_hash = 0;
1433
1434 for (order = 1; order < cds_lfht_get_count_order_ulong(size) + 1; order++) {
1435 len = 1UL << (order - 1);
1436 cds_lfht_alloc_bucket_table(ht, order);
1437
1438 for (i = 0; i < len; i++) {
1439 /*
1440 * Now, we are trying to init the node with the
1441 * hash=(len+i) (which is also a bucket with the
1442 * index=(len+i)) and insert it into the hash table,
1443 * so this node has to be inserted after the bucket
1444 * with the index=(len+i)&(len-1)=i. And because there
1445 * is no other non-bucket node nor bucket node with
1446 * larger index/hash inserted, so the bucket node
1447 * being inserted should be inserted directly linked
1448 * after the bucket node with index=i.
1449 */
1450 prev = bucket_at(ht, i);
1451 node = bucket_at(ht, len + i);
1452
1453 dbg_printf("create bucket: order %lu index %lu hash %lu\n",
1454 order, len + i, len + i);
1455 node->reverse_hash = bit_reverse_ulong(len + i);
1456
1457 /* insert after prev */
1458 assert(is_bucket(prev->next));
1459 node->next = prev->next;
1460 prev->next = flag_bucket(node);
1461 }
1462 }
1463 }
1464
1465 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
1466 unsigned long min_nr_alloc_buckets,
1467 unsigned long max_nr_buckets,
1468 int flags,
1469 const struct cds_lfht_mm_type *mm,
1470 const struct rcu_flavor_struct *flavor,
1471 pthread_attr_t *attr)
1472 {
1473 struct cds_lfht *ht;
1474 unsigned long order;
1475
1476 /* min_nr_alloc_buckets must be power of two */
1477 if (!min_nr_alloc_buckets || (min_nr_alloc_buckets & (min_nr_alloc_buckets - 1)))
1478 return NULL;
1479
1480 /* init_size must be power of two */
1481 if (!init_size || (init_size & (init_size - 1)))
1482 return NULL;
1483
1484 /*
1485 * Memory management plugin default.
1486 */
1487 if (!mm) {
1488 if (CAA_BITS_PER_LONG > 32
1489 && max_nr_buckets
1490 && max_nr_buckets <= (1ULL << 32)) {
1491 /*
1492 * For 64-bit architectures, with max number of
1493 * buckets small enough not to use the entire
1494 * 64-bit memory mapping space (and allowing a
1495 * fair number of hash table instances), use the
1496 * mmap allocator, which is faster than the
1497 * order allocator.
1498 */
1499 mm = &cds_lfht_mm_mmap;
1500 } else {
1501 /*
1502 * The fallback is to use the order allocator.
1503 */
1504 mm = &cds_lfht_mm_order;
1505 }
1506 }
1507
1508 /* max_nr_buckets == 0 for order based mm means infinite */
1509 if (mm == &cds_lfht_mm_order && !max_nr_buckets)
1510 max_nr_buckets = 1UL << (MAX_TABLE_ORDER - 1);
1511
1512 /* max_nr_buckets must be power of two */
1513 if (!max_nr_buckets || (max_nr_buckets & (max_nr_buckets - 1)))
1514 return NULL;
1515
1516 min_nr_alloc_buckets = max(min_nr_alloc_buckets, MIN_TABLE_SIZE);
1517 init_size = max(init_size, MIN_TABLE_SIZE);
1518 max_nr_buckets = max(max_nr_buckets, min_nr_alloc_buckets);
1519 init_size = min(init_size, max_nr_buckets);
1520
1521 ht = mm->alloc_cds_lfht(min_nr_alloc_buckets, max_nr_buckets);
1522 assert(ht);
1523 assert(ht->mm == mm);
1524 assert(ht->bucket_at == mm->bucket_at);
1525
1526 ht->flags = flags;
1527 ht->flavor = flavor;
1528 ht->resize_attr = attr;
1529 alloc_split_items_count(ht);
1530 /* this mutex should not nest in read-side C.S. */
1531 pthread_mutex_init(&ht->resize_mutex, NULL);
1532 order = cds_lfht_get_count_order_ulong(init_size);
1533 ht->resize_target = 1UL << order;
1534 cds_lfht_create_bucket(ht, 1UL << order);
1535 ht->size = 1UL << order;
1536 return ht;
1537 }
1538
1539 void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
1540 cds_lfht_match_fct match, const void *key,
1541 struct cds_lfht_iter *iter)
1542 {
1543 struct cds_lfht_node *node, *next, *bucket;
1544 unsigned long reverse_hash, size;
1545
1546 reverse_hash = bit_reverse_ulong(hash);
1547
1548 size = rcu_dereference(ht->size);
1549 bucket = lookup_bucket(ht, size, hash);
1550 /* We can always skip the bucket node initially */
1551 node = rcu_dereference(bucket->next);
1552 node = clear_flag(node);
1553 for (;;) {
1554 if (caa_unlikely(is_end(node))) {
1555 node = next = NULL;
1556 break;
1557 }
1558 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1559 node = next = NULL;
1560 break;
1561 }
1562 next = rcu_dereference(node->next);
1563 assert(node == clear_flag(node));
1564 if (caa_likely(!is_removed(next))
1565 && !is_bucket(next)
1566 && node->reverse_hash == reverse_hash
1567 && caa_likely(match(node, key))) {
1568 break;
1569 }
1570 node = clear_flag(next);
1571 }
1572 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1573 iter->node = node;
1574 iter->next = next;
1575 }
1576
1577 void cds_lfht_next_duplicate(struct cds_lfht *ht, cds_lfht_match_fct match,
1578 const void *key, struct cds_lfht_iter *iter)
1579 {
1580 struct cds_lfht_node *node, *next;
1581 unsigned long reverse_hash;
1582
1583 node = iter->node;
1584 reverse_hash = node->reverse_hash;
1585 next = iter->next;
1586 node = clear_flag(next);
1587
1588 for (;;) {
1589 if (caa_unlikely(is_end(node))) {
1590 node = next = NULL;
1591 break;
1592 }
1593 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1594 node = next = NULL;
1595 break;
1596 }
1597 next = rcu_dereference(node->next);
1598 if (caa_likely(!is_removed(next))
1599 && !is_bucket(next)
1600 && caa_likely(match(node, key))) {
1601 break;
1602 }
1603 node = clear_flag(next);
1604 }
1605 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1606 iter->node = node;
1607 iter->next = next;
1608 }
1609
1610 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1611 {
1612 struct cds_lfht_node *node, *next;
1613
1614 node = clear_flag(iter->next);
1615 for (;;) {
1616 if (caa_unlikely(is_end(node))) {
1617 node = next = NULL;
1618 break;
1619 }
1620 next = rcu_dereference(node->next);
1621 if (caa_likely(!is_removed(next))
1622 && !is_bucket(next)) {
1623 break;
1624 }
1625 node = clear_flag(next);
1626 }
1627 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1628 iter->node = node;
1629 iter->next = next;
1630 }
1631
1632 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1633 {
1634 /*
1635 * Get next after first bucket node. The first bucket node is the
1636 * first node of the linked list.
1637 */
1638 iter->next = bucket_at(ht, 0)->next;
1639 cds_lfht_next(ht, iter);
1640 }
1641
1642 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
1643 struct cds_lfht_node *node)
1644 {
1645 unsigned long size;
1646
1647 node->reverse_hash = bit_reverse_ulong(hash);
1648 size = rcu_dereference(ht->size);
1649 _cds_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0);
1650 ht_count_add(ht, size, hash);
1651 }
1652
1653 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
1654 unsigned long hash,
1655 cds_lfht_match_fct match,
1656 const void *key,
1657 struct cds_lfht_node *node)
1658 {
1659 unsigned long size;
1660 struct cds_lfht_iter iter;
1661
1662 node->reverse_hash = bit_reverse_ulong(hash);
1663 size = rcu_dereference(ht->size);
1664 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1665 if (iter.node == node)
1666 ht_count_add(ht, size, hash);
1667 return iter.node;
1668 }
1669
1670 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
1671 unsigned long hash,
1672 cds_lfht_match_fct match,
1673 const void *key,
1674 struct cds_lfht_node *node)
1675 {
1676 unsigned long size;
1677 struct cds_lfht_iter iter;
1678
1679 node->reverse_hash = bit_reverse_ulong(hash);
1680 size = rcu_dereference(ht->size);
1681 for (;;) {
1682 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1683 if (iter.node == node) {
1684 ht_count_add(ht, size, hash);
1685 return NULL;
1686 }
1687
1688 if (!_cds_lfht_replace(ht, size, iter.node, iter.next, node))
1689 return iter.node;
1690 }
1691 }
1692
1693 int cds_lfht_replace(struct cds_lfht *ht,
1694 struct cds_lfht_iter *old_iter,
1695 unsigned long hash,
1696 cds_lfht_match_fct match,
1697 const void *key,
1698 struct cds_lfht_node *new_node)
1699 {
1700 unsigned long size;
1701
1702 new_node->reverse_hash = bit_reverse_ulong(hash);
1703 if (!old_iter->node)
1704 return -ENOENT;
1705 if (caa_unlikely(old_iter->node->reverse_hash != new_node->reverse_hash))
1706 return -EINVAL;
1707 if (caa_unlikely(!match(old_iter->node, key)))
1708 return -EINVAL;
1709 size = rcu_dereference(ht->size);
1710 return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next,
1711 new_node);
1712 }
1713
1714 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
1715 {
1716 unsigned long size;
1717 int ret;
1718
1719 size = rcu_dereference(ht->size);
1720 ret = _cds_lfht_del(ht, size, node);
1721 if (!ret) {
1722 unsigned long hash;
1723
1724 hash = bit_reverse_ulong(node->reverse_hash);
1725 ht_count_del(ht, size, hash);
1726 }
1727 return ret;
1728 }
1729
1730 int cds_lfht_is_node_deleted(struct cds_lfht_node *node)
1731 {
1732 return is_removed(CMM_LOAD_SHARED(node->next));
1733 }
1734
1735 static
1736 int cds_lfht_delete_bucket(struct cds_lfht *ht)
1737 {
1738 struct cds_lfht_node *node;
1739 unsigned long order, i, size;
1740
1741 /* Check that the table is empty */
1742 node = bucket_at(ht, 0);
1743 do {
1744 node = clear_flag(node)->next;
1745 if (!is_bucket(node))
1746 return -EPERM;
1747 assert(!is_removed(node));
1748 assert(!is_removal_owner(node));
1749 } while (!is_end(node));
1750 /*
1751 * size accessed without rcu_dereference because hash table is
1752 * being destroyed.
1753 */
1754 size = ht->size;
1755 /* Internal sanity check: all nodes left should be buckets */
1756 for (i = 0; i < size; i++) {
1757 node = bucket_at(ht, i);
1758 dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
1759 i, i, bit_reverse_ulong(node->reverse_hash));
1760 assert(is_bucket(node->next));
1761 }
1762
1763 for (order = cds_lfht_get_count_order_ulong(size); (long)order >= 0; order--)
1764 cds_lfht_free_bucket_table(ht, order);
1765
1766 return 0;
1767 }
1768
1769 /*
1770 * Should only be called when no more concurrent readers nor writers can
1771 * possibly access the table.
1772 */
1773 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
1774 {
1775 int ret, was_online;
1776
1777 /* Wait for in-flight resize operations to complete */
1778 _CMM_STORE_SHARED(ht->in_progress_destroy, 1);
1779 cmm_smp_mb(); /* Store destroy before load resize */
1780 was_online = ht->flavor->read_ongoing();
1781 if (was_online)
1782 ht->flavor->thread_offline();
1783 /* Calling with RCU read-side held is an error. */
1784 if (ht->flavor->read_ongoing()) {
1785 ret = -EINVAL;
1786 if (was_online)
1787 ht->flavor->thread_online();
1788 goto end;
1789 }
1790 while (uatomic_read(&ht->in_progress_resize))
1791 poll(NULL, 0, 100); /* wait for 100ms */
1792 if (was_online)
1793 ht->flavor->thread_online();
1794 ret = cds_lfht_delete_bucket(ht);
1795 if (ret)
1796 return ret;
1797 free_split_items_count(ht);
1798 if (attr)
1799 *attr = ht->resize_attr;
1800 ret = pthread_mutex_destroy(&ht->resize_mutex);
1801 if (ret)
1802 ret = -EBUSY;
1803 poison_free(ht);
1804 end:
1805 return ret;
1806 }
1807
1808 void cds_lfht_count_nodes(struct cds_lfht *ht,
1809 long *approx_before,
1810 unsigned long *count,
1811 long *approx_after)
1812 {
1813 struct cds_lfht_node *node, *next;
1814 unsigned long nr_bucket = 0, nr_removed = 0;
1815
1816 *approx_before = 0;
1817 if (ht->split_count) {
1818 int i;
1819
1820 for (i = 0; i < split_count_mask + 1; i++) {
1821 *approx_before += uatomic_read(&ht->split_count[i].add);
1822 *approx_before -= uatomic_read(&ht->split_count[i].del);
1823 }
1824 }
1825
1826 *count = 0;
1827
1828 /* Count non-bucket nodes in the table */
1829 node = bucket_at(ht, 0);
1830 do {
1831 next = rcu_dereference(node->next);
1832 if (is_removed(next)) {
1833 if (!is_bucket(next))
1834 (nr_removed)++;
1835 else
1836 (nr_bucket)++;
1837 } else if (!is_bucket(next))
1838 (*count)++;
1839 else
1840 (nr_bucket)++;
1841 node = clear_flag(next);
1842 } while (!is_end(node));
1843 dbg_printf("number of logically removed nodes: %lu\n", nr_removed);
1844 dbg_printf("number of bucket nodes: %lu\n", nr_bucket);
1845 *approx_after = 0;
1846 if (ht->split_count) {
1847 int i;
1848
1849 for (i = 0; i < split_count_mask + 1; i++) {
1850 *approx_after += uatomic_read(&ht->split_count[i].add);
1851 *approx_after -= uatomic_read(&ht->split_count[i].del);
1852 }
1853 }
1854 }
1855
1856 /* called with resize mutex held */
1857 static
1858 void _do_cds_lfht_grow(struct cds_lfht *ht,
1859 unsigned long old_size, unsigned long new_size)
1860 {
1861 unsigned long old_order, new_order;
1862
1863 old_order = cds_lfht_get_count_order_ulong(old_size);
1864 new_order = cds_lfht_get_count_order_ulong(new_size);
1865 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1866 old_size, old_order, new_size, new_order);
1867 assert(new_size > old_size);
1868 init_table(ht, old_order + 1, new_order);
1869 }
1870
1871 /* called with resize mutex held */
1872 static
1873 void _do_cds_lfht_shrink(struct cds_lfht *ht,
1874 unsigned long old_size, unsigned long new_size)
1875 {
1876 unsigned long old_order, new_order;
1877
1878 new_size = max(new_size, MIN_TABLE_SIZE);
1879 old_order = cds_lfht_get_count_order_ulong(old_size);
1880 new_order = cds_lfht_get_count_order_ulong(new_size);
1881 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1882 old_size, old_order, new_size, new_order);
1883 assert(new_size < old_size);
1884
1885 /* Remove and unlink all bucket nodes to remove. */
1886 fini_table(ht, new_order + 1, old_order);
1887 }
1888
1889
1890 /* called with resize mutex held */
1891 static
1892 void _do_cds_lfht_resize(struct cds_lfht *ht)
1893 {
1894 unsigned long new_size, old_size;
1895
1896 /*
1897 * Resize table, re-do if the target size has changed under us.
1898 */
1899 do {
1900 assert(uatomic_read(&ht->in_progress_resize));
1901 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1902 break;
1903 ht->resize_initiated = 1;
1904 old_size = ht->size;
1905 new_size = CMM_LOAD_SHARED(ht->resize_target);
1906 if (old_size < new_size)
1907 _do_cds_lfht_grow(ht, old_size, new_size);
1908 else if (old_size > new_size)
1909 _do_cds_lfht_shrink(ht, old_size, new_size);
1910 ht->resize_initiated = 0;
1911 /* write resize_initiated before read resize_target */
1912 cmm_smp_mb();
1913 } while (ht->size != CMM_LOAD_SHARED(ht->resize_target));
1914 }
1915
1916 static
1917 unsigned long resize_target_grow(struct cds_lfht *ht, unsigned long new_size)
1918 {
1919 return _uatomic_xchg_monotonic_increase(&ht->resize_target, new_size);
1920 }
1921
1922 static
1923 void resize_target_update_count(struct cds_lfht *ht,
1924 unsigned long count)
1925 {
1926 count = max(count, MIN_TABLE_SIZE);
1927 count = min(count, ht->max_nr_buckets);
1928 uatomic_set(&ht->resize_target, count);
1929 }
1930
1931 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
1932 {
1933 int was_online;
1934
1935 was_online = ht->flavor->read_ongoing();
1936 if (was_online)
1937 ht->flavor->thread_offline();
1938 /* Calling with RCU read-side held is an error. */
1939 if (ht->flavor->read_ongoing()) {
1940 static int print_once;
1941
1942 if (!CMM_LOAD_SHARED(print_once))
1943 fprintf(stderr, "[error] rculfhash: cds_lfht_resize "
1944 "called with RCU read-side lock held.\n");
1945 CMM_STORE_SHARED(print_once, 1);
1946 assert(0);
1947 goto end;
1948 }
1949 resize_target_update_count(ht, new_size);
1950 CMM_STORE_SHARED(ht->resize_initiated, 1);
1951 pthread_mutex_lock(&ht->resize_mutex);
1952 _do_cds_lfht_resize(ht);
1953 pthread_mutex_unlock(&ht->resize_mutex);
1954 end:
1955 if (was_online)
1956 ht->flavor->thread_online();
1957 }
1958
1959 static
1960 void do_resize_cb(struct rcu_head *head)
1961 {
1962 struct rcu_resize_work *work =
1963 caa_container_of(head, struct rcu_resize_work, head);
1964 struct cds_lfht *ht = work->ht;
1965
1966 ht->flavor->thread_offline();
1967 pthread_mutex_lock(&ht->resize_mutex);
1968 _do_cds_lfht_resize(ht);
1969 pthread_mutex_unlock(&ht->resize_mutex);
1970 ht->flavor->thread_online();
1971 poison_free(work);
1972 cmm_smp_mb(); /* finish resize before decrement */
1973 uatomic_dec(&ht->in_progress_resize);
1974 }
1975
1976 static
1977 void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht)
1978 {
1979 struct rcu_resize_work *work;
1980
1981 /* Store resize_target before read resize_initiated */
1982 cmm_smp_mb();
1983 if (!CMM_LOAD_SHARED(ht->resize_initiated)) {
1984 uatomic_inc(&ht->in_progress_resize);
1985 cmm_smp_mb(); /* increment resize count before load destroy */
1986 if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
1987 uatomic_dec(&ht->in_progress_resize);
1988 return;
1989 }
1990 work = malloc(sizeof(*work));
1991 if (work == NULL) {
1992 dbg_printf("error allocating resize work, bailing out\n");
1993 uatomic_dec(&ht->in_progress_resize);
1994 return;
1995 }
1996 work->ht = ht;
1997 ht->flavor->update_call_rcu(&work->head, do_resize_cb);
1998 CMM_STORE_SHARED(ht->resize_initiated, 1);
1999 }
2000 }
2001
2002 static
2003 void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
2004 {
2005 unsigned long target_size = size << growth;
2006
2007 target_size = min(target_size, ht->max_nr_buckets);
2008 if (resize_target_grow(ht, target_size) >= target_size)
2009 return;
2010
2011 __cds_lfht_resize_lazy_launch(ht);
2012 }
2013
2014 /*
2015 * We favor grow operations over shrink. A shrink operation never occurs
2016 * if a grow operation is queued for lazy execution. A grow operation
2017 * cancels any pending shrink lazy execution.
2018 */
2019 static
2020 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
2021 unsigned long count)
2022 {
2023 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
2024 return;
2025 count = max(count, MIN_TABLE_SIZE);
2026 count = min(count, ht->max_nr_buckets);
2027 if (count == size)
2028 return; /* Already the right size, no resize needed */
2029 if (count > size) { /* lazy grow */
2030 if (resize_target_grow(ht, count) >= count)
2031 return;
2032 } else { /* lazy shrink */
2033 for (;;) {
2034 unsigned long s;
2035
2036 s = uatomic_cmpxchg(&ht->resize_target, size, count);
2037 if (s == size)
2038 break; /* no resize needed */
2039 if (s > size)
2040 return; /* growing is/(was just) in progress */
2041 if (s <= count)
2042 return; /* some other thread do shrink */
2043 size = s;
2044 }
2045 }
2046 __cds_lfht_resize_lazy_launch(ht);
2047 }
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