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