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[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 <urcu.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
567 #if defined(HAVE_SYSCONF)
568 static void ht_init_nr_cpus_mask(void)
569 {
570 long maxcpus;
571
572 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
573 if (maxcpus <= 0) {
574 nr_cpus_mask = -2;
575 return;
576 }
577 /*
578 * round up number of CPUs to next power of two, so we
579 * can use & for modulo.
580 */
581 maxcpus = 1UL << cds_lfht_get_count_order_ulong(maxcpus);
582 nr_cpus_mask = maxcpus - 1;
583 }
584 #else /* #if defined(HAVE_SYSCONF) */
585 static void ht_init_nr_cpus_mask(void)
586 {
587 nr_cpus_mask = -2;
588 }
589 #endif /* #else #if defined(HAVE_SYSCONF) */
590
591 static
592 void alloc_split_items_count(struct cds_lfht *ht)
593 {
594 if (nr_cpus_mask == -1) {
595 ht_init_nr_cpus_mask();
596 if (nr_cpus_mask < 0)
597 split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
598 else
599 split_count_mask = nr_cpus_mask;
600 }
601
602 assert(split_count_mask >= 0);
603
604 if (ht->flags & CDS_LFHT_ACCOUNTING) {
605 ht->split_count = calloc(split_count_mask + 1,
606 sizeof(struct ht_items_count));
607 assert(ht->split_count);
608 } else {
609 ht->split_count = NULL;
610 }
611 }
612
613 static
614 void free_split_items_count(struct cds_lfht *ht)
615 {
616 poison_free(ht->split_count);
617 }
618
619 #if defined(HAVE_SCHED_GETCPU)
620 static
621 int ht_get_split_count_index(unsigned long hash)
622 {
623 int cpu;
624
625 assert(split_count_mask >= 0);
626 cpu = sched_getcpu();
627 if (caa_unlikely(cpu < 0))
628 return hash & split_count_mask;
629 else
630 return cpu & split_count_mask;
631 }
632 #else /* #if defined(HAVE_SCHED_GETCPU) */
633 static
634 int ht_get_split_count_index(unsigned long hash)
635 {
636 return hash & split_count_mask;
637 }
638 #endif /* #else #if defined(HAVE_SCHED_GETCPU) */
639
640 static
641 void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash)
642 {
643 unsigned long split_count;
644 int index;
645 long count;
646
647 if (caa_unlikely(!ht->split_count))
648 return;
649 index = ht_get_split_count_index(hash);
650 split_count = uatomic_add_return(&ht->split_count[index].add, 1);
651 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
652 return;
653 /* Only if number of add multiple of 1UL << COUNT_COMMIT_ORDER */
654
655 dbg_printf("add split count %lu\n", split_count);
656 count = uatomic_add_return(&ht->count,
657 1UL << COUNT_COMMIT_ORDER);
658 if (caa_likely(count & (count - 1)))
659 return;
660 /* Only if global count is power of 2 */
661
662 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) < size)
663 return;
664 dbg_printf("add set global %ld\n", count);
665 cds_lfht_resize_lazy_count(ht, size,
666 count >> (CHAIN_LEN_TARGET - 1));
667 }
668
669 static
670 void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
671 {
672 unsigned long split_count;
673 int index;
674 long count;
675
676 if (caa_unlikely(!ht->split_count))
677 return;
678 index = ht_get_split_count_index(hash);
679 split_count = uatomic_add_return(&ht->split_count[index].del, 1);
680 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
681 return;
682 /* Only if number of deletes multiple of 1UL << COUNT_COMMIT_ORDER */
683
684 dbg_printf("del split count %lu\n", split_count);
685 count = uatomic_add_return(&ht->count,
686 -(1UL << COUNT_COMMIT_ORDER));
687 if (caa_likely(count & (count - 1)))
688 return;
689 /* Only if global count is power of 2 */
690
691 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) >= size)
692 return;
693 dbg_printf("del set global %ld\n", count);
694 /*
695 * Don't shrink table if the number of nodes is below a
696 * certain threshold.
697 */
698 if (count < (1UL << COUNT_COMMIT_ORDER) * (split_count_mask + 1))
699 return;
700 cds_lfht_resize_lazy_count(ht, size,
701 count >> (CHAIN_LEN_TARGET - 1));
702 }
703
704 static
705 void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
706 {
707 unsigned long count;
708
709 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
710 return;
711 count = uatomic_read(&ht->count);
712 /*
713 * Use bucket-local length for small table expand and for
714 * environments lacking per-cpu data support.
715 */
716 if (count >= (1UL << COUNT_COMMIT_ORDER))
717 return;
718 if (chain_len > 100)
719 dbg_printf("WARNING: large chain length: %u.\n",
720 chain_len);
721 if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
722 cds_lfht_resize_lazy_grow(ht, size,
723 cds_lfht_get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1)));
724 }
725
726 static
727 struct cds_lfht_node *clear_flag(struct cds_lfht_node *node)
728 {
729 return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK);
730 }
731
732 static
733 int is_removed(struct cds_lfht_node *node)
734 {
735 return ((unsigned long) node) & REMOVED_FLAG;
736 }
737
738 static
739 int is_bucket(struct cds_lfht_node *node)
740 {
741 return ((unsigned long) node) & BUCKET_FLAG;
742 }
743
744 static
745 struct cds_lfht_node *flag_bucket(struct cds_lfht_node *node)
746 {
747 return (struct cds_lfht_node *) (((unsigned long) node) | BUCKET_FLAG);
748 }
749
750 static
751 int is_removal_owner(struct cds_lfht_node *node)
752 {
753 return ((unsigned long) node) & REMOVAL_OWNER_FLAG;
754 }
755
756 static
757 struct cds_lfht_node *flag_removal_owner(struct cds_lfht_node *node)
758 {
759 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVAL_OWNER_FLAG);
760 }
761
762 static
763 struct cds_lfht_node *flag_removed_or_removal_owner(struct cds_lfht_node *node)
764 {
765 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG | REMOVAL_OWNER_FLAG);
766 }
767
768 static
769 struct cds_lfht_node *get_end(void)
770 {
771 return (struct cds_lfht_node *) END_VALUE;
772 }
773
774 static
775 int is_end(struct cds_lfht_node *node)
776 {
777 return clear_flag(node) == (struct cds_lfht_node *) END_VALUE;
778 }
779
780 static
781 unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr,
782 unsigned long v)
783 {
784 unsigned long old1, old2;
785
786 old1 = uatomic_read(ptr);
787 do {
788 old2 = old1;
789 if (old2 >= v)
790 return old2;
791 } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
792 return old2;
793 }
794
795 static
796 void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
797 {
798 return ht->mm->alloc_bucket_table(ht, order);
799 }
800
801 /*
802 * cds_lfht_free_bucket_table() should be called with decreasing order.
803 * When cds_lfht_free_bucket_table(0) is called, it means the whole
804 * lfht is destroyed.
805 */
806 static
807 void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order)
808 {
809 return ht->mm->free_bucket_table(ht, order);
810 }
811
812 static inline
813 struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
814 {
815 return ht->bucket_at(ht, index);
816 }
817
818 static inline
819 struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
820 unsigned long hash)
821 {
822 assert(size > 0);
823 return bucket_at(ht, hash & (size - 1));
824 }
825
826 /*
827 * Remove all logically deleted nodes from a bucket up to a certain node key.
828 */
829 static
830 void _cds_lfht_gc_bucket(struct cds_lfht_node *bucket, struct cds_lfht_node *node)
831 {
832 struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
833
834 assert(!is_bucket(bucket));
835 assert(!is_removed(bucket));
836 assert(!is_bucket(node));
837 assert(!is_removed(node));
838 for (;;) {
839 iter_prev = bucket;
840 /* We can always skip the bucket node initially */
841 iter = rcu_dereference(iter_prev->next);
842 assert(!is_removed(iter));
843 assert(iter_prev->reverse_hash <= node->reverse_hash);
844 /*
845 * We should never be called with bucket (start of chain)
846 * and logically removed node (end of path compression
847 * marker) being the actual same node. This would be a
848 * bug in the algorithm implementation.
849 */
850 assert(bucket != node);
851 for (;;) {
852 if (caa_unlikely(is_end(iter)))
853 return;
854 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
855 return;
856 next = rcu_dereference(clear_flag(iter)->next);
857 if (caa_likely(is_removed(next)))
858 break;
859 iter_prev = clear_flag(iter);
860 iter = next;
861 }
862 assert(!is_removed(iter));
863 if (is_bucket(iter))
864 new_next = flag_bucket(clear_flag(next));
865 else
866 new_next = clear_flag(next);
867 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
868 }
869 }
870
871 static
872 int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
873 struct cds_lfht_node *old_node,
874 struct cds_lfht_node *old_next,
875 struct cds_lfht_node *new_node)
876 {
877 struct cds_lfht_node *bucket, *ret_next;
878
879 if (!old_node) /* Return -ENOENT if asked to replace NULL node */
880 return -ENOENT;
881
882 assert(!is_removed(old_node));
883 assert(!is_bucket(old_node));
884 assert(!is_removed(new_node));
885 assert(!is_bucket(new_node));
886 assert(new_node != old_node);
887 for (;;) {
888 /* Insert after node to be replaced */
889 if (is_removed(old_next)) {
890 /*
891 * Too late, the old node has been removed under us
892 * between lookup and replace. Fail.
893 */
894 return -ENOENT;
895 }
896 assert(old_next == clear_flag(old_next));
897 assert(new_node != old_next);
898 /*
899 * REMOVAL_OWNER flag is _NEVER_ set before the REMOVED
900 * flag. It is either set atomically at the same time
901 * (replace) or after (del).
902 */
903 assert(!is_removal_owner(old_next));
904 new_node->next = old_next;
905 /*
906 * Here is the whole trick for lock-free replace: we add
907 * the replacement node _after_ the node we want to
908 * replace by atomically setting its next pointer at the
909 * same time we set its removal flag. Given that
910 * the lookups/get next use an iterator aware of the
911 * next pointer, they will either skip the old node due
912 * to the removal flag and see the new node, or use
913 * the old node, but will not see the new one.
914 * This is a replacement of a node with another node
915 * that has the same value: we are therefore not
916 * removing a value from the hash table. We set both the
917 * REMOVED and REMOVAL_OWNER flags atomically so we own
918 * the node after successful cmpxchg.
919 */
920 ret_next = uatomic_cmpxchg(&old_node->next,
921 old_next, flag_removed_or_removal_owner(new_node));
922 if (ret_next == old_next)
923 break; /* We performed the replacement. */
924 old_next = ret_next;
925 }
926
927 /*
928 * Ensure that the old node is not visible to readers anymore:
929 * lookup for the node, and remove it (along with any other
930 * logically removed node) if found.
931 */
932 bucket = lookup_bucket(ht, size, bit_reverse_ulong(old_node->reverse_hash));
933 _cds_lfht_gc_bucket(bucket, new_node);
934
935 assert(is_removed(CMM_LOAD_SHARED(old_node->next)));
936 return 0;
937 }
938
939 /*
940 * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
941 * mode. A NULL unique_ret allows creation of duplicate keys.
942 */
943 static
944 void _cds_lfht_add(struct cds_lfht *ht,
945 unsigned long hash,
946 cds_lfht_match_fct match,
947 const void *key,
948 unsigned long size,
949 struct cds_lfht_node *node,
950 struct cds_lfht_iter *unique_ret,
951 int bucket_flag)
952 {
953 struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
954 *return_node;
955 struct cds_lfht_node *bucket;
956
957 assert(!is_bucket(node));
958 assert(!is_removed(node));
959 bucket = lookup_bucket(ht, size, hash);
960 for (;;) {
961 uint32_t chain_len = 0;
962
963 /*
964 * iter_prev points to the non-removed node prior to the
965 * insert location.
966 */
967 iter_prev = bucket;
968 /* We can always skip the bucket node initially */
969 iter = rcu_dereference(iter_prev->next);
970 assert(iter_prev->reverse_hash <= node->reverse_hash);
971 for (;;) {
972 if (caa_unlikely(is_end(iter)))
973 goto insert;
974 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
975 goto insert;
976
977 /* bucket node is the first node of the identical-hash-value chain */
978 if (bucket_flag && clear_flag(iter)->reverse_hash == node->reverse_hash)
979 goto insert;
980
981 next = rcu_dereference(clear_flag(iter)->next);
982 if (caa_unlikely(is_removed(next)))
983 goto gc_node;
984
985 /* uniquely add */
986 if (unique_ret
987 && !is_bucket(next)
988 && clear_flag(iter)->reverse_hash == node->reverse_hash) {
989 struct cds_lfht_iter d_iter = { .node = node, .next = iter, };
990
991 /*
992 * uniquely adding inserts the node as the first
993 * node of the identical-hash-value node chain.
994 *
995 * This semantic ensures no duplicated keys
996 * should ever be observable in the table
997 * (including traversing the table node by
998 * node by forward iterations)
999 */
1000 cds_lfht_next_duplicate(ht, match, key, &d_iter);
1001 if (!d_iter.node)
1002 goto insert;
1003
1004 *unique_ret = d_iter;
1005 return;
1006 }
1007
1008 /* Only account for identical reverse hash once */
1009 if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash
1010 && !is_bucket(next))
1011 check_resize(ht, size, ++chain_len);
1012 iter_prev = clear_flag(iter);
1013 iter = next;
1014 }
1015
1016 insert:
1017 assert(node != clear_flag(iter));
1018 assert(!is_removed(iter_prev));
1019 assert(!is_removed(iter));
1020 assert(iter_prev != node);
1021 if (!bucket_flag)
1022 node->next = clear_flag(iter);
1023 else
1024 node->next = flag_bucket(clear_flag(iter));
1025 if (is_bucket(iter))
1026 new_node = flag_bucket(node);
1027 else
1028 new_node = node;
1029 if (uatomic_cmpxchg(&iter_prev->next, iter,
1030 new_node) != iter) {
1031 continue; /* retry */
1032 } else {
1033 return_node = node;
1034 goto end;
1035 }
1036
1037 gc_node:
1038 assert(!is_removed(iter));
1039 if (is_bucket(iter))
1040 new_next = flag_bucket(clear_flag(next));
1041 else
1042 new_next = clear_flag(next);
1043 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
1044 /* retry */
1045 }
1046 end:
1047 if (unique_ret) {
1048 unique_ret->node = return_node;
1049 /* unique_ret->next left unset, never used. */
1050 }
1051 }
1052
1053 static
1054 int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
1055 struct cds_lfht_node *node)
1056 {
1057 struct cds_lfht_node *bucket, *next;
1058
1059 if (!node) /* Return -ENOENT if asked to delete NULL node */
1060 return -ENOENT;
1061
1062 /* logically delete the node */
1063 assert(!is_bucket(node));
1064 assert(!is_removed(node));
1065 assert(!is_removal_owner(node));
1066
1067 /*
1068 * We are first checking if the node had previously been
1069 * logically removed (this check is not atomic with setting the
1070 * logical removal flag). Return -ENOENT if the node had
1071 * previously been removed.
1072 */
1073 next = CMM_LOAD_SHARED(node->next); /* next is not dereferenced */
1074 if (caa_unlikely(is_removed(next)))
1075 return -ENOENT;
1076 assert(!is_bucket(next));
1077 /*
1078 * The del operation semantic guarantees a full memory barrier
1079 * before the uatomic_or atomic commit of the deletion flag.
1080 */
1081 cmm_smp_mb__before_uatomic_or();
1082 /*
1083 * We set the REMOVED_FLAG unconditionally. Note that there may
1084 * be more than one concurrent thread setting this flag.
1085 * Knowing which wins the race will be known after the garbage
1086 * collection phase, stay tuned!
1087 */
1088 uatomic_or(&node->next, REMOVED_FLAG);
1089 /* We performed the (logical) deletion. */
1090
1091 /*
1092 * Ensure that the node is not visible to readers anymore: lookup for
1093 * the node, and remove it (along with any other logically removed node)
1094 * if found.
1095 */
1096 bucket = lookup_bucket(ht, size, bit_reverse_ulong(node->reverse_hash));
1097 _cds_lfht_gc_bucket(bucket, node);
1098
1099 assert(is_removed(CMM_LOAD_SHARED(node->next)));
1100 /*
1101 * Last phase: atomically exchange node->next with a version
1102 * having "REMOVAL_OWNER_FLAG" set. If the returned node->next
1103 * pointer did _not_ have "REMOVAL_OWNER_FLAG" set, we now own
1104 * the node and win the removal race.
1105 * It is interesting to note that all "add" paths are forbidden
1106 * to change the next pointer starting from the point where the
1107 * REMOVED_FLAG is set, so here using a read, followed by a
1108 * xchg() suffice to guarantee that the xchg() will ever only
1109 * set the "REMOVAL_OWNER_FLAG" (or change nothing if the flag
1110 * was already set).
1111 */
1112 if (!is_removal_owner(uatomic_xchg(&node->next,
1113 flag_removal_owner(node->next))))
1114 return 0;
1115 else
1116 return -ENOENT;
1117 }
1118
1119 static
1120 void *partition_resize_thread(void *arg)
1121 {
1122 struct partition_resize_work *work = arg;
1123
1124 work->ht->flavor->register_thread();
1125 work->fct(work->ht, work->i, work->start, work->len);
1126 work->ht->flavor->unregister_thread();
1127 return NULL;
1128 }
1129
1130 static
1131 void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
1132 unsigned long len,
1133 void (*fct)(struct cds_lfht *ht, unsigned long i,
1134 unsigned long start, unsigned long len))
1135 {
1136 unsigned long partition_len;
1137 struct partition_resize_work *work;
1138 int thread, ret;
1139 unsigned long nr_threads;
1140
1141 /*
1142 * Note: nr_cpus_mask + 1 is always power of 2.
1143 * We spawn just the number of threads we need to satisfy the minimum
1144 * partition size, up to the number of CPUs in the system.
1145 */
1146 if (nr_cpus_mask > 0) {
1147 nr_threads = min(nr_cpus_mask + 1,
1148 len >> MIN_PARTITION_PER_THREAD_ORDER);
1149 } else {
1150 nr_threads = 1;
1151 }
1152 partition_len = len >> cds_lfht_get_count_order_ulong(nr_threads);
1153 work = calloc(nr_threads, sizeof(*work));
1154 assert(work);
1155 for (thread = 0; thread < nr_threads; thread++) {
1156 work[thread].ht = ht;
1157 work[thread].i = i;
1158 work[thread].len = partition_len;
1159 work[thread].start = thread * partition_len;
1160 work[thread].fct = fct;
1161 ret = pthread_create(&(work[thread].thread_id), ht->resize_attr,
1162 partition_resize_thread, &work[thread]);
1163 assert(!ret);
1164 }
1165 for (thread = 0; thread < nr_threads; thread++) {
1166 ret = pthread_join(work[thread].thread_id, NULL);
1167 assert(!ret);
1168 }
1169 free(work);
1170 }
1171
1172 /*
1173 * Holding RCU read lock to protect _cds_lfht_add against memory
1174 * reclaim that could be performed by other call_rcu worker threads (ABA
1175 * problem).
1176 *
1177 * When we reach a certain length, we can split this population phase over
1178 * many worker threads, based on the number of CPUs available in the system.
1179 * This should therefore take care of not having the expand lagging behind too
1180 * many concurrent insertion threads by using the scheduler's ability to
1181 * schedule bucket node population fairly with insertions.
1182 */
1183 static
1184 void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
1185 unsigned long start, unsigned long len)
1186 {
1187 unsigned long j, size = 1UL << (i - 1);
1188
1189 assert(i > MIN_TABLE_ORDER);
1190 ht->flavor->read_lock();
1191 for (j = size + start; j < size + start + len; j++) {
1192 struct cds_lfht_node *new_node = bucket_at(ht, j);
1193
1194 assert(j >= size && j < (size << 1));
1195 dbg_printf("init populate: order %lu index %lu hash %lu\n",
1196 i, j, j);
1197 new_node->reverse_hash = bit_reverse_ulong(j);
1198 _cds_lfht_add(ht, j, NULL, NULL, size, new_node, NULL, 1);
1199 }
1200 ht->flavor->read_unlock();
1201 }
1202
1203 static
1204 void init_table_populate(struct cds_lfht *ht, unsigned long i,
1205 unsigned long len)
1206 {
1207 assert(nr_cpus_mask != -1);
1208 if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) {
1209 ht->flavor->thread_online();
1210 init_table_populate_partition(ht, i, 0, len);
1211 ht->flavor->thread_offline();
1212 return;
1213 }
1214 partition_resize_helper(ht, i, len, init_table_populate_partition);
1215 }
1216
1217 static
1218 void init_table(struct cds_lfht *ht,
1219 unsigned long first_order, unsigned long last_order)
1220 {
1221 unsigned long i;
1222
1223 dbg_printf("init table: first_order %lu last_order %lu\n",
1224 first_order, last_order);
1225 assert(first_order > MIN_TABLE_ORDER);
1226 for (i = first_order; i <= last_order; i++) {
1227 unsigned long len;
1228
1229 len = 1UL << (i - 1);
1230 dbg_printf("init order %lu len: %lu\n", i, len);
1231
1232 /* Stop expand if the resize target changes under us */
1233 if (CMM_LOAD_SHARED(ht->resize_target) < (1UL << i))
1234 break;
1235
1236 cds_lfht_alloc_bucket_table(ht, i);
1237
1238 /*
1239 * Set all bucket nodes reverse hash values for a level and
1240 * link all bucket nodes into the table.
1241 */
1242 init_table_populate(ht, i, len);
1243
1244 /*
1245 * Update table size.
1246 */
1247 cmm_smp_wmb(); /* populate data before RCU size */
1248 CMM_STORE_SHARED(ht->size, 1UL << i);
1249
1250 dbg_printf("init new size: %lu\n", 1UL << i);
1251 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1252 break;
1253 }
1254 }
1255
1256 /*
1257 * Holding RCU read lock to protect _cds_lfht_remove against memory
1258 * reclaim that could be performed by other call_rcu worker threads (ABA
1259 * problem).
1260 * For a single level, we logically remove and garbage collect each node.
1261 *
1262 * As a design choice, we perform logical removal and garbage collection on a
1263 * node-per-node basis to simplify this algorithm. We also assume keeping good
1264 * cache locality of the operation would overweight possible performance gain
1265 * that could be achieved by batching garbage collection for multiple levels.
1266 * However, this would have to be justified by benchmarks.
1267 *
1268 * Concurrent removal and add operations are helping us perform garbage
1269 * collection of logically removed nodes. We guarantee that all logically
1270 * removed nodes have been garbage-collected (unlinked) before call_rcu is
1271 * invoked to free a hole level of bucket nodes (after a grace period).
1272 *
1273 * Logical removal and garbage collection can therefore be done in batch
1274 * or on a node-per-node basis, as long as the guarantee above holds.
1275 *
1276 * When we reach a certain length, we can split this removal over many worker
1277 * threads, based on the number of CPUs available in the system. This should
1278 * take care of not letting resize process lag behind too many concurrent
1279 * updater threads actively inserting into the hash table.
1280 */
1281 static
1282 void remove_table_partition(struct cds_lfht *ht, unsigned long i,
1283 unsigned long start, unsigned long len)
1284 {
1285 unsigned long j, size = 1UL << (i - 1);
1286
1287 assert(i > MIN_TABLE_ORDER);
1288 ht->flavor->read_lock();
1289 for (j = size + start; j < size + start + len; j++) {
1290 struct cds_lfht_node *fini_bucket = bucket_at(ht, j);
1291 struct cds_lfht_node *parent_bucket = bucket_at(ht, j - size);
1292
1293 assert(j >= size && j < (size << 1));
1294 dbg_printf("remove entry: order %lu index %lu hash %lu\n",
1295 i, j, j);
1296 /* Set the REMOVED_FLAG to freeze the ->next for gc */
1297 uatomic_or(&fini_bucket->next, REMOVED_FLAG);
1298 _cds_lfht_gc_bucket(parent_bucket, fini_bucket);
1299 }
1300 ht->flavor->read_unlock();
1301 }
1302
1303 static
1304 void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
1305 {
1306
1307 assert(nr_cpus_mask != -1);
1308 if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) {
1309 ht->flavor->thread_online();
1310 remove_table_partition(ht, i, 0, len);
1311 ht->flavor->thread_offline();
1312 return;
1313 }
1314 partition_resize_helper(ht, i, len, remove_table_partition);
1315 }
1316
1317 /*
1318 * fini_table() is never called for first_order == 0, which is why
1319 * free_by_rcu_order == 0 can be used as criterion to know if free must
1320 * be called.
1321 */
1322 static
1323 void fini_table(struct cds_lfht *ht,
1324 unsigned long first_order, unsigned long last_order)
1325 {
1326 long i;
1327 unsigned long free_by_rcu_order = 0;
1328
1329 dbg_printf("fini table: first_order %lu last_order %lu\n",
1330 first_order, last_order);
1331 assert(first_order > MIN_TABLE_ORDER);
1332 for (i = last_order; i >= first_order; i--) {
1333 unsigned long len;
1334
1335 len = 1UL << (i - 1);
1336 dbg_printf("fini order %lu len: %lu\n", i, len);
1337
1338 /* Stop shrink if the resize target changes under us */
1339 if (CMM_LOAD_SHARED(ht->resize_target) > (1UL << (i - 1)))
1340 break;
1341
1342 cmm_smp_wmb(); /* populate data before RCU size */
1343 CMM_STORE_SHARED(ht->size, 1UL << (i - 1));
1344
1345 /*
1346 * We need to wait for all add operations to reach Q.S. (and
1347 * thus use the new table for lookups) before we can start
1348 * releasing the old bucket nodes. Otherwise their lookup will
1349 * return a logically removed node as insert position.
1350 */
1351 ht->flavor->update_synchronize_rcu();
1352 if (free_by_rcu_order)
1353 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
1354
1355 /*
1356 * Set "removed" flag in bucket nodes about to be removed.
1357 * Unlink all now-logically-removed bucket node pointers.
1358 * Concurrent add/remove operation are helping us doing
1359 * the gc.
1360 */
1361 remove_table(ht, i, len);
1362
1363 free_by_rcu_order = i;
1364
1365 dbg_printf("fini new size: %lu\n", 1UL << i);
1366 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1367 break;
1368 }
1369
1370 if (free_by_rcu_order) {
1371 ht->flavor->update_synchronize_rcu();
1372 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
1373 }
1374 }
1375
1376 static
1377 void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size)
1378 {
1379 struct cds_lfht_node *prev, *node;
1380 unsigned long order, len, i;
1381
1382 cds_lfht_alloc_bucket_table(ht, 0);
1383
1384 dbg_printf("create bucket: order 0 index 0 hash 0\n");
1385 node = bucket_at(ht, 0);
1386 node->next = flag_bucket(get_end());
1387 node->reverse_hash = 0;
1388
1389 for (order = 1; order < cds_lfht_get_count_order_ulong(size) + 1; order++) {
1390 len = 1UL << (order - 1);
1391 cds_lfht_alloc_bucket_table(ht, order);
1392
1393 for (i = 0; i < len; i++) {
1394 /*
1395 * Now, we are trying to init the node with the
1396 * hash=(len+i) (which is also a bucket with the
1397 * index=(len+i)) and insert it into the hash table,
1398 * so this node has to be inserted after the bucket
1399 * with the index=(len+i)&(len-1)=i. And because there
1400 * is no other non-bucket node nor bucket node with
1401 * larger index/hash inserted, so the bucket node
1402 * being inserted should be inserted directly linked
1403 * after the bucket node with index=i.
1404 */
1405 prev = bucket_at(ht, i);
1406 node = bucket_at(ht, len + i);
1407
1408 dbg_printf("create bucket: order %lu index %lu hash %lu\n",
1409 order, len + i, len + i);
1410 node->reverse_hash = bit_reverse_ulong(len + i);
1411
1412 /* insert after prev */
1413 assert(is_bucket(prev->next));
1414 node->next = prev->next;
1415 prev->next = flag_bucket(node);
1416 }
1417 }
1418 }
1419
1420 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
1421 unsigned long min_nr_alloc_buckets,
1422 unsigned long max_nr_buckets,
1423 int flags,
1424 const struct cds_lfht_mm_type *mm,
1425 const struct rcu_flavor_struct *flavor,
1426 pthread_attr_t *attr)
1427 {
1428 struct cds_lfht *ht;
1429 unsigned long order;
1430
1431 /* min_nr_alloc_buckets must be power of two */
1432 if (!min_nr_alloc_buckets || (min_nr_alloc_buckets & (min_nr_alloc_buckets - 1)))
1433 return NULL;
1434
1435 /* init_size must be power of two */
1436 if (!init_size || (init_size & (init_size - 1)))
1437 return NULL;
1438
1439 /*
1440 * Memory management plugin default.
1441 */
1442 if (!mm) {
1443 if (CAA_BITS_PER_LONG > 32
1444 && max_nr_buckets
1445 && max_nr_buckets <= (1ULL << 32)) {
1446 /*
1447 * For 64-bit architectures, with max number of
1448 * buckets small enough not to use the entire
1449 * 64-bit memory mapping space (and allowing a
1450 * fair number of hash table instances), use the
1451 * mmap allocator, which is faster than the
1452 * order allocator.
1453 */
1454 mm = &cds_lfht_mm_mmap;
1455 } else {
1456 /*
1457 * The fallback is to use the order allocator.
1458 */
1459 mm = &cds_lfht_mm_order;
1460 }
1461 }
1462
1463 /* max_nr_buckets == 0 for order based mm means infinite */
1464 if (mm == &cds_lfht_mm_order && !max_nr_buckets)
1465 max_nr_buckets = 1UL << (MAX_TABLE_ORDER - 1);
1466
1467 /* max_nr_buckets must be power of two */
1468 if (!max_nr_buckets || (max_nr_buckets & (max_nr_buckets - 1)))
1469 return NULL;
1470
1471 min_nr_alloc_buckets = max(min_nr_alloc_buckets, MIN_TABLE_SIZE);
1472 init_size = max(init_size, MIN_TABLE_SIZE);
1473 max_nr_buckets = max(max_nr_buckets, min_nr_alloc_buckets);
1474 init_size = min(init_size, max_nr_buckets);
1475
1476 ht = mm->alloc_cds_lfht(min_nr_alloc_buckets, max_nr_buckets);
1477 assert(ht);
1478 assert(ht->mm == mm);
1479 assert(ht->bucket_at == mm->bucket_at);
1480
1481 ht->flags = flags;
1482 ht->flavor = flavor;
1483 ht->resize_attr = attr;
1484 alloc_split_items_count(ht);
1485 /* this mutex should not nest in read-side C.S. */
1486 pthread_mutex_init(&ht->resize_mutex, NULL);
1487 order = cds_lfht_get_count_order_ulong(init_size);
1488 ht->resize_target = 1UL << order;
1489 cds_lfht_create_bucket(ht, 1UL << order);
1490 ht->size = 1UL << order;
1491 return ht;
1492 }
1493
1494 void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
1495 cds_lfht_match_fct match, const void *key,
1496 struct cds_lfht_iter *iter)
1497 {
1498 struct cds_lfht_node *node, *next, *bucket;
1499 unsigned long reverse_hash, size;
1500
1501 reverse_hash = bit_reverse_ulong(hash);
1502
1503 size = rcu_dereference(ht->size);
1504 bucket = lookup_bucket(ht, size, hash);
1505 /* We can always skip the bucket node initially */
1506 node = rcu_dereference(bucket->next);
1507 node = clear_flag(node);
1508 for (;;) {
1509 if (caa_unlikely(is_end(node))) {
1510 node = next = NULL;
1511 break;
1512 }
1513 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1514 node = next = NULL;
1515 break;
1516 }
1517 next = rcu_dereference(node->next);
1518 assert(node == clear_flag(node));
1519 if (caa_likely(!is_removed(next))
1520 && !is_bucket(next)
1521 && node->reverse_hash == reverse_hash
1522 && caa_likely(match(node, key))) {
1523 break;
1524 }
1525 node = clear_flag(next);
1526 }
1527 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1528 iter->node = node;
1529 iter->next = next;
1530 }
1531
1532 void cds_lfht_next_duplicate(struct cds_lfht *ht, cds_lfht_match_fct match,
1533 const void *key, struct cds_lfht_iter *iter)
1534 {
1535 struct cds_lfht_node *node, *next;
1536 unsigned long reverse_hash;
1537
1538 node = iter->node;
1539 reverse_hash = node->reverse_hash;
1540 next = iter->next;
1541 node = clear_flag(next);
1542
1543 for (;;) {
1544 if (caa_unlikely(is_end(node))) {
1545 node = next = NULL;
1546 break;
1547 }
1548 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1549 node = next = NULL;
1550 break;
1551 }
1552 next = rcu_dereference(node->next);
1553 if (caa_likely(!is_removed(next))
1554 && !is_bucket(next)
1555 && caa_likely(match(node, key))) {
1556 break;
1557 }
1558 node = clear_flag(next);
1559 }
1560 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1561 iter->node = node;
1562 iter->next = next;
1563 }
1564
1565 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1566 {
1567 struct cds_lfht_node *node, *next;
1568
1569 node = clear_flag(iter->next);
1570 for (;;) {
1571 if (caa_unlikely(is_end(node))) {
1572 node = next = NULL;
1573 break;
1574 }
1575 next = rcu_dereference(node->next);
1576 if (caa_likely(!is_removed(next))
1577 && !is_bucket(next)) {
1578 break;
1579 }
1580 node = clear_flag(next);
1581 }
1582 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1583 iter->node = node;
1584 iter->next = next;
1585 }
1586
1587 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1588 {
1589 /*
1590 * Get next after first bucket node. The first bucket node is the
1591 * first node of the linked list.
1592 */
1593 iter->next = bucket_at(ht, 0)->next;
1594 cds_lfht_next(ht, iter);
1595 }
1596
1597 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
1598 struct cds_lfht_node *node)
1599 {
1600 unsigned long size;
1601
1602 node->reverse_hash = bit_reverse_ulong(hash);
1603 size = rcu_dereference(ht->size);
1604 _cds_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0);
1605 ht_count_add(ht, size, hash);
1606 }
1607
1608 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
1609 unsigned long hash,
1610 cds_lfht_match_fct match,
1611 const void *key,
1612 struct cds_lfht_node *node)
1613 {
1614 unsigned long size;
1615 struct cds_lfht_iter iter;
1616
1617 node->reverse_hash = bit_reverse_ulong(hash);
1618 size = rcu_dereference(ht->size);
1619 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1620 if (iter.node == node)
1621 ht_count_add(ht, size, hash);
1622 return iter.node;
1623 }
1624
1625 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
1626 unsigned long hash,
1627 cds_lfht_match_fct match,
1628 const void *key,
1629 struct cds_lfht_node *node)
1630 {
1631 unsigned long size;
1632 struct cds_lfht_iter iter;
1633
1634 node->reverse_hash = bit_reverse_ulong(hash);
1635 size = rcu_dereference(ht->size);
1636 for (;;) {
1637 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1638 if (iter.node == node) {
1639 ht_count_add(ht, size, hash);
1640 return NULL;
1641 }
1642
1643 if (!_cds_lfht_replace(ht, size, iter.node, iter.next, node))
1644 return iter.node;
1645 }
1646 }
1647
1648 int cds_lfht_replace(struct cds_lfht *ht,
1649 struct cds_lfht_iter *old_iter,
1650 unsigned long hash,
1651 cds_lfht_match_fct match,
1652 const void *key,
1653 struct cds_lfht_node *new_node)
1654 {
1655 unsigned long size;
1656
1657 new_node->reverse_hash = bit_reverse_ulong(hash);
1658 if (!old_iter->node)
1659 return -ENOENT;
1660 if (caa_unlikely(old_iter->node->reverse_hash != new_node->reverse_hash))
1661 return -EINVAL;
1662 if (caa_unlikely(!match(old_iter->node, key)))
1663 return -EINVAL;
1664 size = rcu_dereference(ht->size);
1665 return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next,
1666 new_node);
1667 }
1668
1669 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
1670 {
1671 unsigned long size;
1672 int ret;
1673
1674 size = rcu_dereference(ht->size);
1675 ret = _cds_lfht_del(ht, size, node);
1676 if (!ret) {
1677 unsigned long hash;
1678
1679 hash = bit_reverse_ulong(node->reverse_hash);
1680 ht_count_del(ht, size, hash);
1681 }
1682 return ret;
1683 }
1684
1685 int cds_lfht_is_node_deleted(struct cds_lfht_node *node)
1686 {
1687 return is_removed(CMM_LOAD_SHARED(node->next));
1688 }
1689
1690 static
1691 int cds_lfht_delete_bucket(struct cds_lfht *ht)
1692 {
1693 struct cds_lfht_node *node;
1694 unsigned long order, i, size;
1695
1696 /* Check that the table is empty */
1697 node = bucket_at(ht, 0);
1698 do {
1699 node = clear_flag(node)->next;
1700 if (!is_bucket(node))
1701 return -EPERM;
1702 assert(!is_removed(node));
1703 } while (!is_end(node));
1704 /*
1705 * size accessed without rcu_dereference because hash table is
1706 * being destroyed.
1707 */
1708 size = ht->size;
1709 /* Internal sanity check: all nodes left should be buckets */
1710 for (i = 0; i < size; i++) {
1711 node = bucket_at(ht, i);
1712 dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
1713 i, i, bit_reverse_ulong(node->reverse_hash));
1714 assert(is_bucket(node->next));
1715 }
1716
1717 for (order = cds_lfht_get_count_order_ulong(size); (long)order >= 0; order--)
1718 cds_lfht_free_bucket_table(ht, order);
1719
1720 return 0;
1721 }
1722
1723 /*
1724 * Should only be called when no more concurrent readers nor writers can
1725 * possibly access the table.
1726 */
1727 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
1728 {
1729 int ret;
1730
1731 /* Wait for in-flight resize operations to complete */
1732 _CMM_STORE_SHARED(ht->in_progress_destroy, 1);
1733 cmm_smp_mb(); /* Store destroy before load resize */
1734 ht->flavor->thread_offline();
1735 while (uatomic_read(&ht->in_progress_resize))
1736 poll(NULL, 0, 100); /* wait for 100ms */
1737 ht->flavor->thread_online();
1738 ret = cds_lfht_delete_bucket(ht);
1739 if (ret)
1740 return ret;
1741 free_split_items_count(ht);
1742 if (attr)
1743 *attr = ht->resize_attr;
1744 poison_free(ht);
1745 return ret;
1746 }
1747
1748 void cds_lfht_count_nodes(struct cds_lfht *ht,
1749 long *approx_before,
1750 unsigned long *count,
1751 long *approx_after)
1752 {
1753 struct cds_lfht_node *node, *next;
1754 unsigned long nr_bucket = 0, nr_removed = 0;
1755
1756 *approx_before = 0;
1757 if (ht->split_count) {
1758 int i;
1759
1760 for (i = 0; i < split_count_mask + 1; i++) {
1761 *approx_before += uatomic_read(&ht->split_count[i].add);
1762 *approx_before -= uatomic_read(&ht->split_count[i].del);
1763 }
1764 }
1765
1766 *count = 0;
1767
1768 /* Count non-bucket nodes in the table */
1769 node = bucket_at(ht, 0);
1770 do {
1771 next = rcu_dereference(node->next);
1772 if (is_removed(next)) {
1773 if (!is_bucket(next))
1774 (nr_removed)++;
1775 else
1776 (nr_bucket)++;
1777 } else if (!is_bucket(next))
1778 (*count)++;
1779 else
1780 (nr_bucket)++;
1781 node = clear_flag(next);
1782 } while (!is_end(node));
1783 dbg_printf("number of logically removed nodes: %lu\n", nr_removed);
1784 dbg_printf("number of bucket nodes: %lu\n", nr_bucket);
1785 *approx_after = 0;
1786 if (ht->split_count) {
1787 int i;
1788
1789 for (i = 0; i < split_count_mask + 1; i++) {
1790 *approx_after += uatomic_read(&ht->split_count[i].add);
1791 *approx_after -= uatomic_read(&ht->split_count[i].del);
1792 }
1793 }
1794 }
1795
1796 /* called with resize mutex held */
1797 static
1798 void _do_cds_lfht_grow(struct cds_lfht *ht,
1799 unsigned long old_size, unsigned long new_size)
1800 {
1801 unsigned long old_order, new_order;
1802
1803 old_order = cds_lfht_get_count_order_ulong(old_size);
1804 new_order = cds_lfht_get_count_order_ulong(new_size);
1805 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1806 old_size, old_order, new_size, new_order);
1807 assert(new_size > old_size);
1808 init_table(ht, old_order + 1, new_order);
1809 }
1810
1811 /* called with resize mutex held */
1812 static
1813 void _do_cds_lfht_shrink(struct cds_lfht *ht,
1814 unsigned long old_size, unsigned long new_size)
1815 {
1816 unsigned long old_order, new_order;
1817
1818 new_size = max(new_size, MIN_TABLE_SIZE);
1819 old_order = cds_lfht_get_count_order_ulong(old_size);
1820 new_order = cds_lfht_get_count_order_ulong(new_size);
1821 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1822 old_size, old_order, new_size, new_order);
1823 assert(new_size < old_size);
1824
1825 /* Remove and unlink all bucket nodes to remove. */
1826 fini_table(ht, new_order + 1, old_order);
1827 }
1828
1829
1830 /* called with resize mutex held */
1831 static
1832 void _do_cds_lfht_resize(struct cds_lfht *ht)
1833 {
1834 unsigned long new_size, old_size;
1835
1836 /*
1837 * Resize table, re-do if the target size has changed under us.
1838 */
1839 do {
1840 assert(uatomic_read(&ht->in_progress_resize));
1841 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1842 break;
1843 ht->resize_initiated = 1;
1844 old_size = ht->size;
1845 new_size = CMM_LOAD_SHARED(ht->resize_target);
1846 if (old_size < new_size)
1847 _do_cds_lfht_grow(ht, old_size, new_size);
1848 else if (old_size > new_size)
1849 _do_cds_lfht_shrink(ht, old_size, new_size);
1850 ht->resize_initiated = 0;
1851 /* write resize_initiated before read resize_target */
1852 cmm_smp_mb();
1853 } while (ht->size != CMM_LOAD_SHARED(ht->resize_target));
1854 }
1855
1856 static
1857 unsigned long resize_target_grow(struct cds_lfht *ht, unsigned long new_size)
1858 {
1859 return _uatomic_xchg_monotonic_increase(&ht->resize_target, new_size);
1860 }
1861
1862 static
1863 void resize_target_update_count(struct cds_lfht *ht,
1864 unsigned long count)
1865 {
1866 count = max(count, MIN_TABLE_SIZE);
1867 count = min(count, ht->max_nr_buckets);
1868 uatomic_set(&ht->resize_target, count);
1869 }
1870
1871 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
1872 {
1873 resize_target_update_count(ht, new_size);
1874 CMM_STORE_SHARED(ht->resize_initiated, 1);
1875 ht->flavor->thread_offline();
1876 pthread_mutex_lock(&ht->resize_mutex);
1877 _do_cds_lfht_resize(ht);
1878 pthread_mutex_unlock(&ht->resize_mutex);
1879 ht->flavor->thread_online();
1880 }
1881
1882 static
1883 void do_resize_cb(struct rcu_head *head)
1884 {
1885 struct rcu_resize_work *work =
1886 caa_container_of(head, struct rcu_resize_work, head);
1887 struct cds_lfht *ht = work->ht;
1888
1889 ht->flavor->thread_offline();
1890 pthread_mutex_lock(&ht->resize_mutex);
1891 _do_cds_lfht_resize(ht);
1892 pthread_mutex_unlock(&ht->resize_mutex);
1893 ht->flavor->thread_online();
1894 poison_free(work);
1895 cmm_smp_mb(); /* finish resize before decrement */
1896 uatomic_dec(&ht->in_progress_resize);
1897 }
1898
1899 static
1900 void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht)
1901 {
1902 struct rcu_resize_work *work;
1903
1904 /* Store resize_target before read resize_initiated */
1905 cmm_smp_mb();
1906 if (!CMM_LOAD_SHARED(ht->resize_initiated)) {
1907 uatomic_inc(&ht->in_progress_resize);
1908 cmm_smp_mb(); /* increment resize count before load destroy */
1909 if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
1910 uatomic_dec(&ht->in_progress_resize);
1911 return;
1912 }
1913 work = malloc(sizeof(*work));
1914 if (work == NULL) {
1915 dbg_printf("error allocating resize work, bailing out\n");
1916 uatomic_dec(&ht->in_progress_resize);
1917 return;
1918 }
1919 work->ht = ht;
1920 ht->flavor->update_call_rcu(&work->head, do_resize_cb);
1921 CMM_STORE_SHARED(ht->resize_initiated, 1);
1922 }
1923 }
1924
1925 static
1926 void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
1927 {
1928 unsigned long target_size = size << growth;
1929
1930 target_size = min(target_size, ht->max_nr_buckets);
1931 if (resize_target_grow(ht, target_size) >= target_size)
1932 return;
1933
1934 __cds_lfht_resize_lazy_launch(ht);
1935 }
1936
1937 /*
1938 * We favor grow operations over shrink. A shrink operation never occurs
1939 * if a grow operation is queued for lazy execution. A grow operation
1940 * cancels any pending shrink lazy execution.
1941 */
1942 static
1943 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
1944 unsigned long count)
1945 {
1946 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
1947 return;
1948 count = max(count, MIN_TABLE_SIZE);
1949 count = min(count, ht->max_nr_buckets);
1950 if (count == size)
1951 return; /* Already the right size, no resize needed */
1952 if (count > size) { /* lazy grow */
1953 if (resize_target_grow(ht, count) >= count)
1954 return;
1955 } else { /* lazy shrink */
1956 for (;;) {
1957 unsigned long s;
1958
1959 s = uatomic_cmpxchg(&ht->resize_target, size, count);
1960 if (s == size)
1961 break; /* no resize needed */
1962 if (s > size)
1963 return; /* growing is/(was just) in progress */
1964 if (s <= count)
1965 return; /* some other thread do shrink */
1966 size = s;
1967 }
1968 }
1969 __cds_lfht_resize_lazy_launch(ht);
1970 }
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