8942c80ba8c6e8eb5f155cd49e10c22d8455ee23
[urcu.git] / src / rculfhash.c
1 /*
2 * rculfhash.c
3 *
4 * Userspace RCU library - Lock-Free Resizable RCU Hash Table
5 *
6 * Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
7 * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
8 *
9 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * This library is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this library; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24 /*
25 * Based on the following articles:
26 * - Ori Shalev and Nir Shavit. Split-ordered lists: Lock-free
27 * extensible hash tables. J. ACM 53, 3 (May 2006), 379-405.
28 * - Michael, M. M. High performance dynamic lock-free hash tables
29 * and list-based sets. In Proceedings of the fourteenth annual ACM
30 * symposium on Parallel algorithms and architectures, ACM Press,
31 * (2002), 73-82.
32 *
33 * Some specificities of this Lock-Free Resizable RCU Hash Table
34 * implementation:
35 *
36 * - RCU read-side critical section allows readers to perform hash
37 * table lookups, as well as traversals, and use the returned objects
38 * safely by allowing memory reclaim to take place only after a grace
39 * period.
40 * - Add and remove operations are lock-free, and do not need to
41 * allocate memory. They need to be executed within RCU read-side
42 * critical section to ensure the objects they read are valid and to
43 * deal with the cmpxchg ABA problem.
44 * - add and add_unique operations are supported. add_unique checks if
45 * the node key already exists in the hash table. It ensures not to
46 * populate a duplicate key if the node key already exists in the hash
47 * table.
48 * - The resize operation executes concurrently with
49 * add/add_unique/add_replace/remove/lookup/traversal.
50 * - Hash table nodes are contained within a split-ordered list. This
51 * list is ordered by incrementing reversed-bits-hash value.
52 * - An index of bucket nodes is kept. These bucket nodes are the hash
53 * table "buckets". These buckets are internal nodes that allow to
54 * perform a fast hash lookup, similarly to a skip list. These
55 * buckets are chained together in the split-ordered list, which
56 * allows recursive expansion by inserting new buckets between the
57 * existing buckets. The split-ordered list allows adding new buckets
58 * between existing buckets as the table needs to grow.
59 * - The resize operation for small tables only allows expanding the
60 * hash table. It is triggered automatically by detecting long chains
61 * in the add operation.
62 * - The resize operation for larger tables (and available through an
63 * API) allows both expanding and shrinking the hash table.
64 * - Split-counters are used to keep track of the number of
65 * nodes within the hash table for automatic resize triggering.
66 * - Resize operation initiated by long chain detection is executed by a
67 * worker thread, which keeps lock-freedom of add and remove.
68 * - Resize operations are protected by a mutex.
69 * - The removal operation is split in two parts: first, a "removed"
70 * flag is set in the next pointer within the node to remove. Then,
71 * a "garbage collection" is performed in the bucket containing the
72 * removed node (from the start of the bucket up to the removed node).
73 * All encountered nodes with "removed" flag set in their next
74 * pointers are removed from the linked-list. If the cmpxchg used for
75 * removal fails (due to concurrent garbage-collection or concurrent
76 * add), we retry from the beginning of the bucket. This ensures that
77 * the node with "removed" flag set is removed from the hash table
78 * (not visible to lookups anymore) before the RCU read-side critical
79 * section held across removal ends. Furthermore, this ensures that
80 * the node with "removed" flag set is removed from the linked-list
81 * before its memory is reclaimed. After setting the "removal" flag,
82 * only the thread which removal is the first to set the "removal
83 * owner" flag (with an xchg) into a node's next pointer is considered
84 * to have succeeded its removal (and thus owns the node to reclaim).
85 * Because we garbage-collect starting from an invariant node (the
86 * start-of-bucket bucket node) up to the "removed" node (or find a
87 * reverse-hash that is higher), we are sure that a successful
88 * traversal of the chain leads to a chain that is present in the
89 * linked-list (the start node is never removed) and that it does not
90 * contain the "removed" node anymore, even if concurrent delete/add
91 * operations are changing the structure of the list concurrently.
92 * - The add operations perform garbage collection of buckets if they
93 * encounter nodes with removed flag set in the bucket where they want
94 * to add their new node. This ensures lock-freedom of add operation by
95 * helping the remover unlink nodes from the list rather than to wait
96 * for it do to so.
97 * - There are three memory backends for the hash table buckets: the
98 * "order table", the "chunks", and the "mmap".
99 * - These bucket containers contain a compact version of the hash table
100 * nodes.
101 * - The RCU "order table":
102 * - has a first level table indexed by log2(hash index) which is
103 * copied and expanded by the resize operation. This order table
104 * allows finding the "bucket node" tables.
105 * - There is one bucket node table per hash index order. The size of
106 * each bucket node table is half the number of hashes contained in
107 * this order (except for order 0).
108 * - The RCU "chunks" is best suited for close interaction with a page
109 * allocator. It uses a linear array as index to "chunks" containing
110 * each the same number of buckets.
111 * - The RCU "mmap" memory backend uses a single memory map to hold
112 * all buckets.
113 * - synchronize_rcu is used to garbage-collect the old bucket node table.
114 *
115 * Ordering Guarantees:
116 *
117 * To discuss these guarantees, we first define "read" operation as any
118 * of the the basic cds_lfht_lookup, cds_lfht_next_duplicate,
119 * cds_lfht_first, cds_lfht_next operation, as well as
120 * cds_lfht_add_unique (failure).
121 *
122 * We define "read traversal" operation as any of the following
123 * group of operations
124 * - cds_lfht_lookup followed by iteration with cds_lfht_next_duplicate
125 * (and/or cds_lfht_next, although less common).
126 * - cds_lfht_add_unique (failure) followed by iteration with
127 * cds_lfht_next_duplicate (and/or cds_lfht_next, although less
128 * common).
129 * - cds_lfht_first followed iteration with cds_lfht_next (and/or
130 * cds_lfht_next_duplicate, although less common).
131 *
132 * We define "write" operations as any of cds_lfht_add, cds_lfht_replace,
133 * cds_lfht_add_unique (success), cds_lfht_add_replace, cds_lfht_del.
134 *
135 * When cds_lfht_add_unique succeeds (returns the node passed as
136 * parameter), it acts as a "write" operation. When cds_lfht_add_unique
137 * fails (returns a node different from the one passed as parameter), it
138 * acts as a "read" operation. A cds_lfht_add_unique failure is a
139 * cds_lfht_lookup "read" operation, therefore, any ordering guarantee
140 * referring to "lookup" imply any of "lookup" or cds_lfht_add_unique
141 * (failure).
142 *
143 * We define "prior" and "later" node as nodes observable by reads and
144 * read traversals respectively before and after a write or sequence of
145 * write operations.
146 *
147 * Hash-table operations are often cascaded, for example, the pointer
148 * returned by a cds_lfht_lookup() might be passed to a cds_lfht_next(),
149 * whose return value might in turn be passed to another hash-table
150 * operation. This entire cascaded series of operations must be enclosed
151 * by a pair of matching rcu_read_lock() and rcu_read_unlock()
152 * operations.
153 *
154 * The following ordering guarantees are offered by this hash table:
155 *
156 * A.1) "read" after "write": if there is ordering between a write and a
157 * later read, then the read is guaranteed to see the write or some
158 * later write.
159 * A.2) "read traversal" after "write": given that there is dependency
160 * ordering between reads in a "read traversal", if there is
161 * ordering between a write and the first read of the traversal,
162 * then the "read traversal" is guaranteed to see the write or
163 * some later write.
164 * B.1) "write" after "read": if there is ordering between a read and a
165 * later write, then the read will never see the write.
166 * B.2) "write" after "read traversal": given that there is dependency
167 * ordering between reads in a "read traversal", if there is
168 * ordering between the last read of the traversal and a later
169 * write, then the "read traversal" will never see the write.
170 * C) "write" while "read traversal": if a write occurs during a "read
171 * traversal", the traversal may, or may not, see the write.
172 * D.1) "write" after "write": if there is ordering between a write and
173 * a later write, then the later write is guaranteed to see the
174 * effects of the first write.
175 * D.2) Concurrent "write" pairs: The system will assign an arbitrary
176 * order to any pair of concurrent conflicting writes.
177 * Non-conflicting writes (for example, to different keys) are
178 * unordered.
179 * E) If a grace period separates a "del" or "replace" operation
180 * and a subsequent operation, then that subsequent operation is
181 * guaranteed not to see the removed item.
182 * F) Uniqueness guarantee: given a hash table that does not contain
183 * duplicate items for a given key, there will only be one item in
184 * the hash table after an arbitrary sequence of add_unique and/or
185 * add_replace operations. Note, however, that a pair of
186 * concurrent read operations might well access two different items
187 * with that key.
188 * G.1) If a pair of lookups for a given key are ordered (e.g. by a
189 * memory barrier), then the second lookup will return the same
190 * node as the previous lookup, or some later node.
191 * G.2) A "read traversal" that starts after the end of a prior "read
192 * traversal" (ordered by memory barriers) is guaranteed to see the
193 * same nodes as the previous traversal, or some later nodes.
194 * G.3) Concurrent "read" pairs: concurrent reads are unordered. For
195 * example, if a pair of reads to the same key run concurrently
196 * with an insertion of that same key, the reads remain unordered
197 * regardless of their return values. In other words, you cannot
198 * rely on the values returned by the reads to deduce ordering.
199 *
200 * Progress guarantees:
201 *
202 * * Reads are wait-free. These operations always move forward in the
203 * hash table linked list, and this list has no loop.
204 * * Writes are lock-free. Any retry loop performed by a write operation
205 * is triggered by progress made within another update operation.
206 *
207 * Bucket node tables:
208 *
209 * hash table hash table the last all bucket node tables
210 * order size bucket node 0 1 2 3 4 5 6(index)
211 * table size
212 * 0 1 1 1
213 * 1 2 1 1 1
214 * 2 4 2 1 1 2
215 * 3 8 4 1 1 2 4
216 * 4 16 8 1 1 2 4 8
217 * 5 32 16 1 1 2 4 8 16
218 * 6 64 32 1 1 2 4 8 16 32
219 *
220 * When growing/shrinking, we only focus on the last bucket node table
221 * which size is (!order ? 1 : (1 << (order -1))).
222 *
223 * Example for growing/shrinking:
224 * grow hash table from order 5 to 6: init the index=6 bucket node table
225 * shrink hash table from order 6 to 5: fini the index=6 bucket node table
226 *
227 * A bit of ascii art explanation:
228 *
229 * The order index is the off-by-one compared to the actual power of 2
230 * because we use index 0 to deal with the 0 special-case.
231 *
232 * This shows the nodes for a small table ordered by reversed bits:
233 *
234 * bits reverse
235 * 0 000 000
236 * 4 100 001
237 * 2 010 010
238 * 6 110 011
239 * 1 001 100
240 * 5 101 101
241 * 3 011 110
242 * 7 111 111
243 *
244 * This shows the nodes in order of non-reversed bits, linked by
245 * reversed-bit order.
246 *
247 * order bits reverse
248 * 0 0 000 000
249 * 1 | 1 001 100 <-
250 * 2 | | 2 010 010 <- |
251 * | | | 3 011 110 | <- |
252 * 3 -> | | | 4 100 001 | |
253 * -> | | 5 101 101 |
254 * -> | 6 110 011
255 * -> 7 111 111
256 */
257
258 #define _LGPL_SOURCE
259 #include <stdlib.h>
260 #include <errno.h>
261 #include <assert.h>
262 #include <stdio.h>
263 #include <stdint.h>
264 #include <string.h>
265 #include <sched.h>
266 #include <unistd.h>
267
268 #include "compat-getcpu.h"
269 #include <urcu/pointer.h>
270 #include <urcu/call-rcu.h>
271 #include <urcu/flavor.h>
272 #include <urcu/arch.h>
273 #include <urcu/uatomic.h>
274 #include <urcu/compiler.h>
275 #include <urcu/rculfhash.h>
276 #include <rculfhash-internal.h>
277 #include <stdio.h>
278 #include <pthread.h>
279 #include <signal.h>
280 #include "workqueue.h"
281 #include "urcu-die.h"
282
283 /*
284 * Split-counters lazily update the global counter each 1024
285 * addition/removal. It automatically keeps track of resize required.
286 * We use the bucket length as indicator for need to expand for small
287 * tables and machines lacking per-cpu data support.
288 */
289 #define COUNT_COMMIT_ORDER 10
290 #define DEFAULT_SPLIT_COUNT_MASK 0xFUL
291 #define CHAIN_LEN_TARGET 1
292 #define CHAIN_LEN_RESIZE_THRESHOLD 3
293
294 /*
295 * Define the minimum table size.
296 */
297 #define MIN_TABLE_ORDER 0
298 #define MIN_TABLE_SIZE (1UL << MIN_TABLE_ORDER)
299
300 /*
301 * Minimum number of bucket nodes to touch per thread to parallelize grow/shrink.
302 */
303 #define MIN_PARTITION_PER_THREAD_ORDER 12
304 #define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
305
306 /*
307 * The removed flag needs to be updated atomically with the pointer.
308 * It indicates that no node must attach to the node scheduled for
309 * removal, and that node garbage collection must be performed.
310 * The bucket flag does not require to be updated atomically with the
311 * pointer, but it is added as a pointer low bit flag to save space.
312 * The "removal owner" flag is used to detect which of the "del"
313 * operation that has set the "removed flag" gets to return the removed
314 * node to its caller. Note that the replace operation does not need to
315 * iteract with the "removal owner" flag, because it validates that
316 * the "removed" flag is not set before performing its cmpxchg.
317 */
318 #define REMOVED_FLAG (1UL << 0)
319 #define BUCKET_FLAG (1UL << 1)
320 #define REMOVAL_OWNER_FLAG (1UL << 2)
321 #define FLAGS_MASK ((1UL << 3) - 1)
322
323 /* Value of the end pointer. Should not interact with flags. */
324 #define END_VALUE NULL
325
326 /*
327 * ht_items_count: Split-counters counting the number of node addition
328 * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
329 * is set at hash table creation.
330 *
331 * These are free-running counters, never reset to zero. They count the
332 * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
333 * operations to update the global counter. We choose a power-of-2 value
334 * for the trigger to deal with 32 or 64-bit overflow of the counter.
335 */
336 struct ht_items_count {
337 unsigned long add, del;
338 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
339
340 /*
341 * resize_work: Contains arguments passed to worker thread
342 * responsible for performing lazy resize.
343 */
344 struct resize_work {
345 struct urcu_work work;
346 struct cds_lfht *ht;
347 };
348
349 /*
350 * partition_resize_work: Contains arguments passed to worker threads
351 * executing the hash table resize on partitions of the hash table
352 * assigned to each processor's worker thread.
353 */
354 struct partition_resize_work {
355 pthread_t thread_id;
356 struct cds_lfht *ht;
357 unsigned long i, start, len;
358 void (*fct)(struct cds_lfht *ht, unsigned long i,
359 unsigned long start, unsigned long len);
360 };
361
362 static struct urcu_workqueue *cds_lfht_workqueue;
363 static unsigned long cds_lfht_workqueue_user_count;
364
365 /*
366 * Mutex ensuring mutual exclusion between workqueue initialization and
367 * fork handlers. cds_lfht_fork_mutex nests inside call_rcu_mutex.
368 */
369 static pthread_mutex_t cds_lfht_fork_mutex = PTHREAD_MUTEX_INITIALIZER;
370
371 static struct urcu_atfork cds_lfht_atfork;
372
373 /*
374 * atfork handler nesting counters. Handle being registered to many urcu
375 * flavors, thus being possibly invoked more than once in the
376 * pthread_atfork list of callbacks.
377 */
378 static int cds_lfht_workqueue_atfork_nesting;
379
380 static void cds_lfht_init_worker(const struct rcu_flavor_struct *flavor);
381 static void cds_lfht_fini_worker(const struct rcu_flavor_struct *flavor);
382
383 #ifdef CONFIG_CDS_LFHT_ITER_DEBUG
384
385 static
386 void cds_lfht_iter_debug_set_ht(struct cds_lfht *ht, struct cds_lfht_iter *iter)
387 {
388 iter->lfht = ht;
389 }
390
391 #define cds_lfht_iter_debug_assert(...) assert(__VA_ARGS__)
392
393 #else
394
395 static
396 void cds_lfht_iter_debug_set_ht(struct cds_lfht *ht, struct cds_lfht_iter *iter)
397 {
398 }
399
400 #define cds_lfht_iter_debug_assert(...)
401
402 #endif
403
404 /*
405 * Algorithm to reverse bits in a word by lookup table, extended to
406 * 64-bit words.
407 * Source:
408 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
409 * Originally from Public Domain.
410 */
411
412 static const uint8_t BitReverseTable256[256] =
413 {
414 #define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
415 #define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
416 #define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
417 R6(0), R6(2), R6(1), R6(3)
418 };
419 #undef R2
420 #undef R4
421 #undef R6
422
423 static
424 uint8_t bit_reverse_u8(uint8_t v)
425 {
426 return BitReverseTable256[v];
427 }
428
429 #if (CAA_BITS_PER_LONG == 32)
430 static
431 uint32_t bit_reverse_u32(uint32_t v)
432 {
433 return ((uint32_t) bit_reverse_u8(v) << 24) |
434 ((uint32_t) bit_reverse_u8(v >> 8) << 16) |
435 ((uint32_t) bit_reverse_u8(v >> 16) << 8) |
436 ((uint32_t) bit_reverse_u8(v >> 24));
437 }
438 #else
439 static
440 uint64_t bit_reverse_u64(uint64_t v)
441 {
442 return ((uint64_t) bit_reverse_u8(v) << 56) |
443 ((uint64_t) bit_reverse_u8(v >> 8) << 48) |
444 ((uint64_t) bit_reverse_u8(v >> 16) << 40) |
445 ((uint64_t) bit_reverse_u8(v >> 24) << 32) |
446 ((uint64_t) bit_reverse_u8(v >> 32) << 24) |
447 ((uint64_t) bit_reverse_u8(v >> 40) << 16) |
448 ((uint64_t) bit_reverse_u8(v >> 48) << 8) |
449 ((uint64_t) bit_reverse_u8(v >> 56));
450 }
451 #endif
452
453 static
454 unsigned long bit_reverse_ulong(unsigned long v)
455 {
456 #if (CAA_BITS_PER_LONG == 32)
457 return bit_reverse_u32(v);
458 #else
459 return bit_reverse_u64(v);
460 #endif
461 }
462
463 /*
464 * fls: returns the position of the most significant bit.
465 * Returns 0 if no bit is set, else returns the position of the most
466 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
467 */
468 #if defined(__i386) || defined(__x86_64)
469 static inline
470 unsigned int fls_u32(uint32_t x)
471 {
472 int r;
473
474 __asm__ ("bsrl %1,%0\n\t"
475 "jnz 1f\n\t"
476 "movl $-1,%0\n\t"
477 "1:\n\t"
478 : "=r" (r) : "rm" (x));
479 return r + 1;
480 }
481 #define HAS_FLS_U32
482 #endif
483
484 #if defined(__x86_64)
485 static inline
486 unsigned int fls_u64(uint64_t x)
487 {
488 long r;
489
490 __asm__ ("bsrq %1,%0\n\t"
491 "jnz 1f\n\t"
492 "movq $-1,%0\n\t"
493 "1:\n\t"
494 : "=r" (r) : "rm" (x));
495 return r + 1;
496 }
497 #define HAS_FLS_U64
498 #endif
499
500 #ifndef HAS_FLS_U64
501 static __attribute__((unused))
502 unsigned int fls_u64(uint64_t x)
503 {
504 unsigned int r = 64;
505
506 if (!x)
507 return 0;
508
509 if (!(x & 0xFFFFFFFF00000000ULL)) {
510 x <<= 32;
511 r -= 32;
512 }
513 if (!(x & 0xFFFF000000000000ULL)) {
514 x <<= 16;
515 r -= 16;
516 }
517 if (!(x & 0xFF00000000000000ULL)) {
518 x <<= 8;
519 r -= 8;
520 }
521 if (!(x & 0xF000000000000000ULL)) {
522 x <<= 4;
523 r -= 4;
524 }
525 if (!(x & 0xC000000000000000ULL)) {
526 x <<= 2;
527 r -= 2;
528 }
529 if (!(x & 0x8000000000000000ULL)) {
530 x <<= 1;
531 r -= 1;
532 }
533 return r;
534 }
535 #endif
536
537 #ifndef HAS_FLS_U32
538 static __attribute__((unused))
539 unsigned int fls_u32(uint32_t x)
540 {
541 unsigned int r = 32;
542
543 if (!x)
544 return 0;
545 if (!(x & 0xFFFF0000U)) {
546 x <<= 16;
547 r -= 16;
548 }
549 if (!(x & 0xFF000000U)) {
550 x <<= 8;
551 r -= 8;
552 }
553 if (!(x & 0xF0000000U)) {
554 x <<= 4;
555 r -= 4;
556 }
557 if (!(x & 0xC0000000U)) {
558 x <<= 2;
559 r -= 2;
560 }
561 if (!(x & 0x80000000U)) {
562 x <<= 1;
563 r -= 1;
564 }
565 return r;
566 }
567 #endif
568
569 unsigned int cds_lfht_fls_ulong(unsigned long x)
570 {
571 #if (CAA_BITS_PER_LONG == 32)
572 return fls_u32(x);
573 #else
574 return fls_u64(x);
575 #endif
576 }
577
578 /*
579 * Return the minimum order for which x <= (1UL << order).
580 * Return -1 if x is 0.
581 */
582 int cds_lfht_get_count_order_u32(uint32_t x)
583 {
584 if (!x)
585 return -1;
586
587 return fls_u32(x - 1);
588 }
589
590 /*
591 * Return the minimum order for which x <= (1UL << order).
592 * Return -1 if x is 0.
593 */
594 int cds_lfht_get_count_order_ulong(unsigned long x)
595 {
596 if (!x)
597 return -1;
598
599 return cds_lfht_fls_ulong(x - 1);
600 }
601
602 static
603 void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth);
604
605 static
606 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
607 unsigned long count);
608
609 static void mutex_lock(pthread_mutex_t *mutex)
610 {
611 int ret;
612
613 #ifndef DISTRUST_SIGNALS_EXTREME
614 ret = pthread_mutex_lock(mutex);
615 if (ret)
616 urcu_die(ret);
617 #else /* #ifndef DISTRUST_SIGNALS_EXTREME */
618 while ((ret = pthread_mutex_trylock(mutex)) != 0) {
619 if (ret != EBUSY && ret != EINTR)
620 urcu_die(ret);
621 if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) {
622 cmm_smp_mb();
623 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
624 cmm_smp_mb();
625 }
626 (void) poll(NULL, 0, 10);
627 }
628 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
629 }
630
631 static void mutex_unlock(pthread_mutex_t *mutex)
632 {
633 int ret;
634
635 ret = pthread_mutex_unlock(mutex);
636 if (ret)
637 urcu_die(ret);
638 }
639
640 static long nr_cpus_mask = -1;
641 static long split_count_mask = -1;
642 static int split_count_order = -1;
643
644 #if defined(HAVE_SYSCONF)
645 static void ht_init_nr_cpus_mask(void)
646 {
647 long maxcpus;
648
649 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
650 if (maxcpus <= 0) {
651 nr_cpus_mask = -2;
652 return;
653 }
654 /*
655 * round up number of CPUs to next power of two, so we
656 * can use & for modulo.
657 */
658 maxcpus = 1UL << cds_lfht_get_count_order_ulong(maxcpus);
659 nr_cpus_mask = maxcpus - 1;
660 }
661 #else /* #if defined(HAVE_SYSCONF) */
662 static void ht_init_nr_cpus_mask(void)
663 {
664 nr_cpus_mask = -2;
665 }
666 #endif /* #else #if defined(HAVE_SYSCONF) */
667
668 static
669 void alloc_split_items_count(struct cds_lfht *ht)
670 {
671 if (nr_cpus_mask == -1) {
672 ht_init_nr_cpus_mask();
673 if (nr_cpus_mask < 0)
674 split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
675 else
676 split_count_mask = nr_cpus_mask;
677 split_count_order =
678 cds_lfht_get_count_order_ulong(split_count_mask + 1);
679 }
680
681 assert(split_count_mask >= 0);
682
683 if (ht->flags & CDS_LFHT_ACCOUNTING) {
684 ht->split_count = calloc(split_count_mask + 1,
685 sizeof(struct ht_items_count));
686 assert(ht->split_count);
687 } else {
688 ht->split_count = NULL;
689 }
690 }
691
692 static
693 void free_split_items_count(struct cds_lfht *ht)
694 {
695 poison_free(ht->split_count);
696 }
697
698 static
699 int ht_get_split_count_index(unsigned long hash)
700 {
701 int cpu;
702
703 assert(split_count_mask >= 0);
704 cpu = urcu_sched_getcpu();
705 if (caa_unlikely(cpu < 0))
706 return hash & split_count_mask;
707 else
708 return cpu & split_count_mask;
709 }
710
711 static
712 void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash)
713 {
714 unsigned long split_count;
715 int index;
716 long count;
717
718 if (caa_unlikely(!ht->split_count))
719 return;
720 index = ht_get_split_count_index(hash);
721 split_count = uatomic_add_return(&ht->split_count[index].add, 1);
722 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
723 return;
724 /* Only if number of add multiple of 1UL << COUNT_COMMIT_ORDER */
725
726 dbg_printf("add split count %lu\n", split_count);
727 count = uatomic_add_return(&ht->count,
728 1UL << COUNT_COMMIT_ORDER);
729 if (caa_likely(count & (count - 1)))
730 return;
731 /* Only if global count is power of 2 */
732
733 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) < size)
734 return;
735 dbg_printf("add set global %ld\n", count);
736 cds_lfht_resize_lazy_count(ht, size,
737 count >> (CHAIN_LEN_TARGET - 1));
738 }
739
740 static
741 void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
742 {
743 unsigned long split_count;
744 int index;
745 long count;
746
747 if (caa_unlikely(!ht->split_count))
748 return;
749 index = ht_get_split_count_index(hash);
750 split_count = uatomic_add_return(&ht->split_count[index].del, 1);
751 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
752 return;
753 /* Only if number of deletes multiple of 1UL << COUNT_COMMIT_ORDER */
754
755 dbg_printf("del split count %lu\n", split_count);
756 count = uatomic_add_return(&ht->count,
757 -(1UL << COUNT_COMMIT_ORDER));
758 if (caa_likely(count & (count - 1)))
759 return;
760 /* Only if global count is power of 2 */
761
762 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) >= size)
763 return;
764 dbg_printf("del set global %ld\n", count);
765 /*
766 * Don't shrink table if the number of nodes is below a
767 * certain threshold.
768 */
769 if (count < (1UL << COUNT_COMMIT_ORDER) * (split_count_mask + 1))
770 return;
771 cds_lfht_resize_lazy_count(ht, size,
772 count >> (CHAIN_LEN_TARGET - 1));
773 }
774
775 static
776 void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
777 {
778 unsigned long count;
779
780 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
781 return;
782 count = uatomic_read(&ht->count);
783 /*
784 * Use bucket-local length for small table expand and for
785 * environments lacking per-cpu data support.
786 */
787 if (count >= (1UL << (COUNT_COMMIT_ORDER + split_count_order)))
788 return;
789 if (chain_len > 100)
790 dbg_printf("WARNING: large chain length: %u.\n",
791 chain_len);
792 if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD) {
793 int growth;
794
795 /*
796 * Ideal growth calculated based on chain length.
797 */
798 growth = cds_lfht_get_count_order_u32(chain_len
799 - (CHAIN_LEN_TARGET - 1));
800 if ((ht->flags & CDS_LFHT_ACCOUNTING)
801 && (size << growth)
802 >= (1UL << (COUNT_COMMIT_ORDER
803 + split_count_order))) {
804 /*
805 * If ideal growth expands the hash table size
806 * beyond the "small hash table" sizes, use the
807 * maximum small hash table size to attempt
808 * expanding the hash table. This only applies
809 * when node accounting is available, otherwise
810 * the chain length is used to expand the hash
811 * table in every case.
812 */
813 growth = COUNT_COMMIT_ORDER + split_count_order
814 - cds_lfht_get_count_order_ulong(size);
815 if (growth <= 0)
816 return;
817 }
818 cds_lfht_resize_lazy_grow(ht, size, growth);
819 }
820 }
821
822 static
823 struct cds_lfht_node *clear_flag(struct cds_lfht_node *node)
824 {
825 return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK);
826 }
827
828 static
829 int is_removed(struct cds_lfht_node *node)
830 {
831 return ((unsigned long) node) & REMOVED_FLAG;
832 }
833
834 static
835 int is_bucket(struct cds_lfht_node *node)
836 {
837 return ((unsigned long) node) & BUCKET_FLAG;
838 }
839
840 static
841 struct cds_lfht_node *flag_bucket(struct cds_lfht_node *node)
842 {
843 return (struct cds_lfht_node *) (((unsigned long) node) | BUCKET_FLAG);
844 }
845
846 static
847 int is_removal_owner(struct cds_lfht_node *node)
848 {
849 return ((unsigned long) node) & REMOVAL_OWNER_FLAG;
850 }
851
852 static
853 struct cds_lfht_node *flag_removal_owner(struct cds_lfht_node *node)
854 {
855 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVAL_OWNER_FLAG);
856 }
857
858 static
859 struct cds_lfht_node *flag_removed_or_removal_owner(struct cds_lfht_node *node)
860 {
861 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG | REMOVAL_OWNER_FLAG);
862 }
863
864 static
865 struct cds_lfht_node *get_end(void)
866 {
867 return (struct cds_lfht_node *) END_VALUE;
868 }
869
870 static
871 int is_end(struct cds_lfht_node *node)
872 {
873 return clear_flag(node) == (struct cds_lfht_node *) END_VALUE;
874 }
875
876 static
877 unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr,
878 unsigned long v)
879 {
880 unsigned long old1, old2;
881
882 old1 = uatomic_read(ptr);
883 do {
884 old2 = old1;
885 if (old2 >= v)
886 return old2;
887 } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
888 return old2;
889 }
890
891 static
892 void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
893 {
894 return ht->mm->alloc_bucket_table(ht, order);
895 }
896
897 /*
898 * cds_lfht_free_bucket_table() should be called with decreasing order.
899 * When cds_lfht_free_bucket_table(0) is called, it means the whole
900 * lfht is destroyed.
901 */
902 static
903 void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order)
904 {
905 return ht->mm->free_bucket_table(ht, order);
906 }
907
908 static inline
909 struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
910 {
911 return ht->bucket_at(ht, index);
912 }
913
914 static inline
915 struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
916 unsigned long hash)
917 {
918 assert(size > 0);
919 return bucket_at(ht, hash & (size - 1));
920 }
921
922 /*
923 * Remove all logically deleted nodes from a bucket up to a certain node key.
924 */
925 static
926 void _cds_lfht_gc_bucket(struct cds_lfht_node *bucket, struct cds_lfht_node *node)
927 {
928 struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
929
930 assert(!is_bucket(bucket));
931 assert(!is_removed(bucket));
932 assert(!is_removal_owner(bucket));
933 assert(!is_bucket(node));
934 assert(!is_removed(node));
935 assert(!is_removal_owner(node));
936 for (;;) {
937 iter_prev = bucket;
938 /* We can always skip the bucket node initially */
939 iter = rcu_dereference(iter_prev->next);
940 assert(!is_removed(iter));
941 assert(!is_removal_owner(iter));
942 assert(iter_prev->reverse_hash <= node->reverse_hash);
943 /*
944 * We should never be called with bucket (start of chain)
945 * and logically removed node (end of path compression
946 * marker) being the actual same node. This would be a
947 * bug in the algorithm implementation.
948 */
949 assert(bucket != node);
950 for (;;) {
951 if (caa_unlikely(is_end(iter)))
952 return;
953 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
954 return;
955 next = rcu_dereference(clear_flag(iter)->next);
956 if (caa_likely(is_removed(next)))
957 break;
958 iter_prev = clear_flag(iter);
959 iter = next;
960 }
961 assert(!is_removed(iter));
962 assert(!is_removal_owner(iter));
963 if (is_bucket(iter))
964 new_next = flag_bucket(clear_flag(next));
965 else
966 new_next = clear_flag(next);
967 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
968 }
969 }
970
971 static
972 int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
973 struct cds_lfht_node *old_node,
974 struct cds_lfht_node *old_next,
975 struct cds_lfht_node *new_node)
976 {
977 struct cds_lfht_node *bucket, *ret_next;
978
979 if (!old_node) /* Return -ENOENT if asked to replace NULL node */
980 return -ENOENT;
981
982 assert(!is_removed(old_node));
983 assert(!is_removal_owner(old_node));
984 assert(!is_bucket(old_node));
985 assert(!is_removed(new_node));
986 assert(!is_removal_owner(new_node));
987 assert(!is_bucket(new_node));
988 assert(new_node != old_node);
989 for (;;) {
990 /* Insert after node to be replaced */
991 if (is_removed(old_next)) {
992 /*
993 * Too late, the old node has been removed under us
994 * between lookup and replace. Fail.
995 */
996 return -ENOENT;
997 }
998 assert(old_next == clear_flag(old_next));
999 assert(new_node != old_next);
1000 /*
1001 * REMOVAL_OWNER flag is _NEVER_ set before the REMOVED
1002 * flag. It is either set atomically at the same time
1003 * (replace) or after (del).
1004 */
1005 assert(!is_removal_owner(old_next));
1006 new_node->next = old_next;
1007 /*
1008 * Here is the whole trick for lock-free replace: we add
1009 * the replacement node _after_ the node we want to
1010 * replace by atomically setting its next pointer at the
1011 * same time we set its removal flag. Given that
1012 * the lookups/get next use an iterator aware of the
1013 * next pointer, they will either skip the old node due
1014 * to the removal flag and see the new node, or use
1015 * the old node, but will not see the new one.
1016 * This is a replacement of a node with another node
1017 * that has the same value: we are therefore not
1018 * removing a value from the hash table. We set both the
1019 * REMOVED and REMOVAL_OWNER flags atomically so we own
1020 * the node after successful cmpxchg.
1021 */
1022 ret_next = uatomic_cmpxchg(&old_node->next,
1023 old_next, flag_removed_or_removal_owner(new_node));
1024 if (ret_next == old_next)
1025 break; /* We performed the replacement. */
1026 old_next = ret_next;
1027 }
1028
1029 /*
1030 * Ensure that the old node is not visible to readers anymore:
1031 * lookup for the node, and remove it (along with any other
1032 * logically removed node) if found.
1033 */
1034 bucket = lookup_bucket(ht, size, bit_reverse_ulong(old_node->reverse_hash));
1035 _cds_lfht_gc_bucket(bucket, new_node);
1036
1037 assert(is_removed(CMM_LOAD_SHARED(old_node->next)));
1038 return 0;
1039 }
1040
1041 /*
1042 * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
1043 * mode. A NULL unique_ret allows creation of duplicate keys.
1044 */
1045 static
1046 void _cds_lfht_add(struct cds_lfht *ht,
1047 unsigned long hash,
1048 cds_lfht_match_fct match,
1049 const void *key,
1050 unsigned long size,
1051 struct cds_lfht_node *node,
1052 struct cds_lfht_iter *unique_ret,
1053 int bucket_flag)
1054 {
1055 struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
1056 *return_node;
1057 struct cds_lfht_node *bucket;
1058
1059 assert(!is_bucket(node));
1060 assert(!is_removed(node));
1061 assert(!is_removal_owner(node));
1062 bucket = lookup_bucket(ht, size, hash);
1063 for (;;) {
1064 uint32_t chain_len = 0;
1065
1066 /*
1067 * iter_prev points to the non-removed node prior to the
1068 * insert location.
1069 */
1070 iter_prev = bucket;
1071 /* We can always skip the bucket node initially */
1072 iter = rcu_dereference(iter_prev->next);
1073 assert(iter_prev->reverse_hash <= node->reverse_hash);
1074 for (;;) {
1075 if (caa_unlikely(is_end(iter)))
1076 goto insert;
1077 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
1078 goto insert;
1079
1080 /* bucket node is the first node of the identical-hash-value chain */
1081 if (bucket_flag && clear_flag(iter)->reverse_hash == node->reverse_hash)
1082 goto insert;
1083
1084 next = rcu_dereference(clear_flag(iter)->next);
1085 if (caa_unlikely(is_removed(next)))
1086 goto gc_node;
1087
1088 /* uniquely add */
1089 if (unique_ret
1090 && !is_bucket(next)
1091 && clear_flag(iter)->reverse_hash == node->reverse_hash) {
1092 struct cds_lfht_iter d_iter = {
1093 .node = node,
1094 .next = iter,
1095 #ifdef CONFIG_CDS_LFHT_ITER_DEBUG
1096 .lfht = ht,
1097 #endif
1098 };
1099
1100 /*
1101 * uniquely adding inserts the node as the first
1102 * node of the identical-hash-value node chain.
1103 *
1104 * This semantic ensures no duplicated keys
1105 * should ever be observable in the table
1106 * (including traversing the table node by
1107 * node by forward iterations)
1108 */
1109 cds_lfht_next_duplicate(ht, match, key, &d_iter);
1110 if (!d_iter.node)
1111 goto insert;
1112
1113 *unique_ret = d_iter;
1114 return;
1115 }
1116
1117 /* Only account for identical reverse hash once */
1118 if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash
1119 && !is_bucket(next))
1120 check_resize(ht, size, ++chain_len);
1121 iter_prev = clear_flag(iter);
1122 iter = next;
1123 }
1124
1125 insert:
1126 assert(node != clear_flag(iter));
1127 assert(!is_removed(iter_prev));
1128 assert(!is_removal_owner(iter_prev));
1129 assert(!is_removed(iter));
1130 assert(!is_removal_owner(iter));
1131 assert(iter_prev != node);
1132 if (!bucket_flag)
1133 node->next = clear_flag(iter);
1134 else
1135 node->next = flag_bucket(clear_flag(iter));
1136 if (is_bucket(iter))
1137 new_node = flag_bucket(node);
1138 else
1139 new_node = node;
1140 if (uatomic_cmpxchg(&iter_prev->next, iter,
1141 new_node) != iter) {
1142 continue; /* retry */
1143 } else {
1144 return_node = node;
1145 goto end;
1146 }
1147
1148 gc_node:
1149 assert(!is_removed(iter));
1150 assert(!is_removal_owner(iter));
1151 if (is_bucket(iter))
1152 new_next = flag_bucket(clear_flag(next));
1153 else
1154 new_next = clear_flag(next);
1155 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
1156 /* retry */
1157 }
1158 end:
1159 if (unique_ret) {
1160 unique_ret->node = return_node;
1161 /* unique_ret->next left unset, never used. */
1162 }
1163 }
1164
1165 static
1166 int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
1167 struct cds_lfht_node *node)
1168 {
1169 struct cds_lfht_node *bucket, *next;
1170
1171 if (!node) /* Return -ENOENT if asked to delete NULL node */
1172 return -ENOENT;
1173
1174 /* logically delete the node */
1175 assert(!is_bucket(node));
1176 assert(!is_removed(node));
1177 assert(!is_removal_owner(node));
1178
1179 /*
1180 * We are first checking if the node had previously been
1181 * logically removed (this check is not atomic with setting the
1182 * logical removal flag). Return -ENOENT if the node had
1183 * previously been removed.
1184 */
1185 next = CMM_LOAD_SHARED(node->next); /* next is not dereferenced */
1186 if (caa_unlikely(is_removed(next)))
1187 return -ENOENT;
1188 assert(!is_bucket(next));
1189 /*
1190 * The del operation semantic guarantees a full memory barrier
1191 * before the uatomic_or atomic commit of the deletion flag.
1192 */
1193 cmm_smp_mb__before_uatomic_or();
1194 /*
1195 * We set the REMOVED_FLAG unconditionally. Note that there may
1196 * be more than one concurrent thread setting this flag.
1197 * Knowing which wins the race will be known after the garbage
1198 * collection phase, stay tuned!
1199 */
1200 uatomic_or(&node->next, REMOVED_FLAG);
1201 /* We performed the (logical) deletion. */
1202
1203 /*
1204 * Ensure that the node is not visible to readers anymore: lookup for
1205 * the node, and remove it (along with any other logically removed node)
1206 * if found.
1207 */
1208 bucket = lookup_bucket(ht, size, bit_reverse_ulong(node->reverse_hash));
1209 _cds_lfht_gc_bucket(bucket, node);
1210
1211 assert(is_removed(CMM_LOAD_SHARED(node->next)));
1212 /*
1213 * Last phase: atomically exchange node->next with a version
1214 * having "REMOVAL_OWNER_FLAG" set. If the returned node->next
1215 * pointer did _not_ have "REMOVAL_OWNER_FLAG" set, we now own
1216 * the node and win the removal race.
1217 * It is interesting to note that all "add" paths are forbidden
1218 * to change the next pointer starting from the point where the
1219 * REMOVED_FLAG is set, so here using a read, followed by a
1220 * xchg() suffice to guarantee that the xchg() will ever only
1221 * set the "REMOVAL_OWNER_FLAG" (or change nothing if the flag
1222 * was already set).
1223 */
1224 if (!is_removal_owner(uatomic_xchg(&node->next,
1225 flag_removal_owner(node->next))))
1226 return 0;
1227 else
1228 return -ENOENT;
1229 }
1230
1231 static
1232 void *partition_resize_thread(void *arg)
1233 {
1234 struct partition_resize_work *work = arg;
1235
1236 work->ht->flavor->register_thread();
1237 work->fct(work->ht, work->i, work->start, work->len);
1238 work->ht->flavor->unregister_thread();
1239 return NULL;
1240 }
1241
1242 static
1243 void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
1244 unsigned long len,
1245 void (*fct)(struct cds_lfht *ht, unsigned long i,
1246 unsigned long start, unsigned long len))
1247 {
1248 unsigned long partition_len, start = 0;
1249 struct partition_resize_work *work;
1250 int thread, ret;
1251 unsigned long nr_threads;
1252
1253 assert(nr_cpus_mask != -1);
1254 if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD)
1255 goto fallback;
1256
1257 /*
1258 * Note: nr_cpus_mask + 1 is always power of 2.
1259 * We spawn just the number of threads we need to satisfy the minimum
1260 * partition size, up to the number of CPUs in the system.
1261 */
1262 if (nr_cpus_mask > 0) {
1263 nr_threads = min(nr_cpus_mask + 1,
1264 len >> MIN_PARTITION_PER_THREAD_ORDER);
1265 } else {
1266 nr_threads = 1;
1267 }
1268 partition_len = len >> cds_lfht_get_count_order_ulong(nr_threads);
1269 work = calloc(nr_threads, sizeof(*work));
1270 if (!work) {
1271 dbg_printf("error allocating for resize, single-threading\n");
1272 goto fallback;
1273 }
1274 for (thread = 0; thread < nr_threads; thread++) {
1275 work[thread].ht = ht;
1276 work[thread].i = i;
1277 work[thread].len = partition_len;
1278 work[thread].start = thread * partition_len;
1279 work[thread].fct = fct;
1280 ret = pthread_create(&(work[thread].thread_id), ht->resize_attr,
1281 partition_resize_thread, &work[thread]);
1282 if (ret == EAGAIN) {
1283 /*
1284 * Out of resources: wait and join the threads
1285 * we've created, then handle leftovers.
1286 */
1287 dbg_printf("error spawning for resize, single-threading\n");
1288 start = work[thread].start;
1289 len -= start;
1290 nr_threads = thread;
1291 break;
1292 }
1293 assert(!ret);
1294 }
1295 for (thread = 0; thread < nr_threads; thread++) {
1296 ret = pthread_join(work[thread].thread_id, NULL);
1297 assert(!ret);
1298 }
1299 free(work);
1300
1301 /*
1302 * A pthread_create failure above will either lead in us having
1303 * no threads to join or starting at a non-zero offset,
1304 * fallback to single thread processing of leftovers.
1305 */
1306 if (start == 0 && nr_threads > 0)
1307 return;
1308 fallback:
1309 fct(ht, i, start, len);
1310 }
1311
1312 /*
1313 * Holding RCU read lock to protect _cds_lfht_add against memory
1314 * reclaim that could be performed by other worker threads (ABA
1315 * problem).
1316 *
1317 * When we reach a certain length, we can split this population phase over
1318 * many worker threads, based on the number of CPUs available in the system.
1319 * This should therefore take care of not having the expand lagging behind too
1320 * many concurrent insertion threads by using the scheduler's ability to
1321 * schedule bucket node population fairly with insertions.
1322 */
1323 static
1324 void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
1325 unsigned long start, unsigned long len)
1326 {
1327 unsigned long j, size = 1UL << (i - 1);
1328
1329 assert(i > MIN_TABLE_ORDER);
1330 ht->flavor->read_lock();
1331 for (j = size + start; j < size + start + len; j++) {
1332 struct cds_lfht_node *new_node = bucket_at(ht, j);
1333
1334 assert(j >= size && j < (size << 1));
1335 dbg_printf("init populate: order %lu index %lu hash %lu\n",
1336 i, j, j);
1337 new_node->reverse_hash = bit_reverse_ulong(j);
1338 _cds_lfht_add(ht, j, NULL, NULL, size, new_node, NULL, 1);
1339 }
1340 ht->flavor->read_unlock();
1341 }
1342
1343 static
1344 void init_table_populate(struct cds_lfht *ht, unsigned long i,
1345 unsigned long len)
1346 {
1347 partition_resize_helper(ht, i, len, init_table_populate_partition);
1348 }
1349
1350 static
1351 void init_table(struct cds_lfht *ht,
1352 unsigned long first_order, unsigned long last_order)
1353 {
1354 unsigned long i;
1355
1356 dbg_printf("init table: first_order %lu last_order %lu\n",
1357 first_order, last_order);
1358 assert(first_order > MIN_TABLE_ORDER);
1359 for (i = first_order; i <= last_order; i++) {
1360 unsigned long len;
1361
1362 len = 1UL << (i - 1);
1363 dbg_printf("init order %lu len: %lu\n", i, len);
1364
1365 /* Stop expand if the resize target changes under us */
1366 if (CMM_LOAD_SHARED(ht->resize_target) < (1UL << i))
1367 break;
1368
1369 cds_lfht_alloc_bucket_table(ht, i);
1370
1371 /*
1372 * Set all bucket nodes reverse hash values for a level and
1373 * link all bucket nodes into the table.
1374 */
1375 init_table_populate(ht, i, len);
1376
1377 /*
1378 * Update table size.
1379 */
1380 cmm_smp_wmb(); /* populate data before RCU size */
1381 CMM_STORE_SHARED(ht->size, 1UL << i);
1382
1383 dbg_printf("init new size: %lu\n", 1UL << i);
1384 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1385 break;
1386 }
1387 }
1388
1389 /*
1390 * Holding RCU read lock to protect _cds_lfht_remove against memory
1391 * reclaim that could be performed by other worker threads (ABA
1392 * problem).
1393 * For a single level, we logically remove and garbage collect each node.
1394 *
1395 * As a design choice, we perform logical removal and garbage collection on a
1396 * node-per-node basis to simplify this algorithm. We also assume keeping good
1397 * cache locality of the operation would overweight possible performance gain
1398 * that could be achieved by batching garbage collection for multiple levels.
1399 * However, this would have to be justified by benchmarks.
1400 *
1401 * Concurrent removal and add operations are helping us perform garbage
1402 * collection of logically removed nodes. We guarantee that all logically
1403 * removed nodes have been garbage-collected (unlinked) before work
1404 * enqueue is invoked to free a hole level of bucket nodes (after a
1405 * grace period).
1406 *
1407 * Logical removal and garbage collection can therefore be done in batch
1408 * or on a node-per-node basis, as long as the guarantee above holds.
1409 *
1410 * When we reach a certain length, we can split this removal over many worker
1411 * threads, based on the number of CPUs available in the system. This should
1412 * take care of not letting resize process lag behind too many concurrent
1413 * updater threads actively inserting into the hash table.
1414 */
1415 static
1416 void remove_table_partition(struct cds_lfht *ht, unsigned long i,
1417 unsigned long start, unsigned long len)
1418 {
1419 unsigned long j, size = 1UL << (i - 1);
1420
1421 assert(i > MIN_TABLE_ORDER);
1422 ht->flavor->read_lock();
1423 for (j = size + start; j < size + start + len; j++) {
1424 struct cds_lfht_node *fini_bucket = bucket_at(ht, j);
1425 struct cds_lfht_node *parent_bucket = bucket_at(ht, j - size);
1426
1427 assert(j >= size && j < (size << 1));
1428 dbg_printf("remove entry: order %lu index %lu hash %lu\n",
1429 i, j, j);
1430 /* Set the REMOVED_FLAG to freeze the ->next for gc */
1431 uatomic_or(&fini_bucket->next, REMOVED_FLAG);
1432 _cds_lfht_gc_bucket(parent_bucket, fini_bucket);
1433 }
1434 ht->flavor->read_unlock();
1435 }
1436
1437 static
1438 void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
1439 {
1440 partition_resize_helper(ht, i, len, remove_table_partition);
1441 }
1442
1443 /*
1444 * fini_table() is never called for first_order == 0, which is why
1445 * free_by_rcu_order == 0 can be used as criterion to know if free must
1446 * be called.
1447 */
1448 static
1449 void fini_table(struct cds_lfht *ht,
1450 unsigned long first_order, unsigned long last_order)
1451 {
1452 long i;
1453 unsigned long free_by_rcu_order = 0;
1454
1455 dbg_printf("fini table: first_order %lu last_order %lu\n",
1456 first_order, last_order);
1457 assert(first_order > MIN_TABLE_ORDER);
1458 for (i = last_order; i >= first_order; i--) {
1459 unsigned long len;
1460
1461 len = 1UL << (i - 1);
1462 dbg_printf("fini order %ld len: %lu\n", i, len);
1463
1464 /* Stop shrink if the resize target changes under us */
1465 if (CMM_LOAD_SHARED(ht->resize_target) > (1UL << (i - 1)))
1466 break;
1467
1468 cmm_smp_wmb(); /* populate data before RCU size */
1469 CMM_STORE_SHARED(ht->size, 1UL << (i - 1));
1470
1471 /*
1472 * We need to wait for all add operations to reach Q.S. (and
1473 * thus use the new table for lookups) before we can start
1474 * releasing the old bucket nodes. Otherwise their lookup will
1475 * return a logically removed node as insert position.
1476 */
1477 ht->flavor->update_synchronize_rcu();
1478 if (free_by_rcu_order)
1479 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
1480
1481 /*
1482 * Set "removed" flag in bucket nodes about to be removed.
1483 * Unlink all now-logically-removed bucket node pointers.
1484 * Concurrent add/remove operation are helping us doing
1485 * the gc.
1486 */
1487 remove_table(ht, i, len);
1488
1489 free_by_rcu_order = i;
1490
1491 dbg_printf("fini new size: %lu\n", 1UL << i);
1492 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1493 break;
1494 }
1495
1496 if (free_by_rcu_order) {
1497 ht->flavor->update_synchronize_rcu();
1498 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
1499 }
1500 }
1501
1502 static
1503 void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size)
1504 {
1505 struct cds_lfht_node *prev, *node;
1506 unsigned long order, len, i;
1507
1508 cds_lfht_alloc_bucket_table(ht, 0);
1509
1510 dbg_printf("create bucket: order 0 index 0 hash 0\n");
1511 node = bucket_at(ht, 0);
1512 node->next = flag_bucket(get_end());
1513 node->reverse_hash = 0;
1514
1515 for (order = 1; order < cds_lfht_get_count_order_ulong(size) + 1; order++) {
1516 len = 1UL << (order - 1);
1517 cds_lfht_alloc_bucket_table(ht, order);
1518
1519 for (i = 0; i < len; i++) {
1520 /*
1521 * Now, we are trying to init the node with the
1522 * hash=(len+i) (which is also a bucket with the
1523 * index=(len+i)) and insert it into the hash table,
1524 * so this node has to be inserted after the bucket
1525 * with the index=(len+i)&(len-1)=i. And because there
1526 * is no other non-bucket node nor bucket node with
1527 * larger index/hash inserted, so the bucket node
1528 * being inserted should be inserted directly linked
1529 * after the bucket node with index=i.
1530 */
1531 prev = bucket_at(ht, i);
1532 node = bucket_at(ht, len + i);
1533
1534 dbg_printf("create bucket: order %lu index %lu hash %lu\n",
1535 order, len + i, len + i);
1536 node->reverse_hash = bit_reverse_ulong(len + i);
1537
1538 /* insert after prev */
1539 assert(is_bucket(prev->next));
1540 node->next = prev->next;
1541 prev->next = flag_bucket(node);
1542 }
1543 }
1544 }
1545
1546 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
1547 unsigned long min_nr_alloc_buckets,
1548 unsigned long max_nr_buckets,
1549 int flags,
1550 const struct cds_lfht_mm_type *mm,
1551 const struct rcu_flavor_struct *flavor,
1552 pthread_attr_t *attr)
1553 {
1554 struct cds_lfht *ht;
1555 unsigned long order;
1556
1557 /* min_nr_alloc_buckets must be power of two */
1558 if (!min_nr_alloc_buckets || (min_nr_alloc_buckets & (min_nr_alloc_buckets - 1)))
1559 return NULL;
1560
1561 /* init_size must be power of two */
1562 if (!init_size || (init_size & (init_size - 1)))
1563 return NULL;
1564
1565 /*
1566 * Memory management plugin default.
1567 */
1568 if (!mm) {
1569 if (CAA_BITS_PER_LONG > 32
1570 && max_nr_buckets
1571 && max_nr_buckets <= (1ULL << 32)) {
1572 /*
1573 * For 64-bit architectures, with max number of
1574 * buckets small enough not to use the entire
1575 * 64-bit memory mapping space (and allowing a
1576 * fair number of hash table instances), use the
1577 * mmap allocator, which is faster than the
1578 * order allocator.
1579 */
1580 mm = &cds_lfht_mm_mmap;
1581 } else {
1582 /*
1583 * The fallback is to use the order allocator.
1584 */
1585 mm = &cds_lfht_mm_order;
1586 }
1587 }
1588
1589 /* max_nr_buckets == 0 for order based mm means infinite */
1590 if (mm == &cds_lfht_mm_order && !max_nr_buckets)
1591 max_nr_buckets = 1UL << (MAX_TABLE_ORDER - 1);
1592
1593 /* max_nr_buckets must be power of two */
1594 if (!max_nr_buckets || (max_nr_buckets & (max_nr_buckets - 1)))
1595 return NULL;
1596
1597 if (flags & CDS_LFHT_AUTO_RESIZE)
1598 cds_lfht_init_worker(flavor);
1599
1600 min_nr_alloc_buckets = max(min_nr_alloc_buckets, MIN_TABLE_SIZE);
1601 init_size = max(init_size, MIN_TABLE_SIZE);
1602 max_nr_buckets = max(max_nr_buckets, min_nr_alloc_buckets);
1603 init_size = min(init_size, max_nr_buckets);
1604
1605 ht = mm->alloc_cds_lfht(min_nr_alloc_buckets, max_nr_buckets);
1606 assert(ht);
1607 assert(ht->mm == mm);
1608 assert(ht->bucket_at == mm->bucket_at);
1609
1610 ht->flags = flags;
1611 ht->flavor = flavor;
1612 ht->resize_attr = attr;
1613 alloc_split_items_count(ht);
1614 /* this mutex should not nest in read-side C.S. */
1615 pthread_mutex_init(&ht->resize_mutex, NULL);
1616 order = cds_lfht_get_count_order_ulong(init_size);
1617 ht->resize_target = 1UL << order;
1618 cds_lfht_create_bucket(ht, 1UL << order);
1619 ht->size = 1UL << order;
1620 return ht;
1621 }
1622
1623 void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
1624 cds_lfht_match_fct match, const void *key,
1625 struct cds_lfht_iter *iter)
1626 {
1627 struct cds_lfht_node *node, *next, *bucket;
1628 unsigned long reverse_hash, size;
1629
1630 cds_lfht_iter_debug_set_ht(ht, iter);
1631
1632 reverse_hash = bit_reverse_ulong(hash);
1633
1634 size = rcu_dereference(ht->size);
1635 bucket = lookup_bucket(ht, size, hash);
1636 /* We can always skip the bucket node initially */
1637 node = rcu_dereference(bucket->next);
1638 node = clear_flag(node);
1639 for (;;) {
1640 if (caa_unlikely(is_end(node))) {
1641 node = next = NULL;
1642 break;
1643 }
1644 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1645 node = next = NULL;
1646 break;
1647 }
1648 next = rcu_dereference(node->next);
1649 assert(node == clear_flag(node));
1650 if (caa_likely(!is_removed(next))
1651 && !is_bucket(next)
1652 && node->reverse_hash == reverse_hash
1653 && caa_likely(match(node, key))) {
1654 break;
1655 }
1656 node = clear_flag(next);
1657 }
1658 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1659 iter->node = node;
1660 iter->next = next;
1661 }
1662
1663 void cds_lfht_next_duplicate(struct cds_lfht *ht, cds_lfht_match_fct match,
1664 const void *key, struct cds_lfht_iter *iter)
1665 {
1666 struct cds_lfht_node *node, *next;
1667 unsigned long reverse_hash;
1668
1669 cds_lfht_iter_debug_assert(ht == iter->lfht);
1670 node = iter->node;
1671 reverse_hash = node->reverse_hash;
1672 next = iter->next;
1673 node = clear_flag(next);
1674
1675 for (;;) {
1676 if (caa_unlikely(is_end(node))) {
1677 node = next = NULL;
1678 break;
1679 }
1680 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1681 node = next = NULL;
1682 break;
1683 }
1684 next = rcu_dereference(node->next);
1685 if (caa_likely(!is_removed(next))
1686 && !is_bucket(next)
1687 && caa_likely(match(node, key))) {
1688 break;
1689 }
1690 node = clear_flag(next);
1691 }
1692 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1693 iter->node = node;
1694 iter->next = next;
1695 }
1696
1697 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1698 {
1699 struct cds_lfht_node *node, *next;
1700
1701 cds_lfht_iter_debug_assert(ht == iter->lfht);
1702 node = clear_flag(iter->next);
1703 for (;;) {
1704 if (caa_unlikely(is_end(node))) {
1705 node = next = NULL;
1706 break;
1707 }
1708 next = rcu_dereference(node->next);
1709 if (caa_likely(!is_removed(next))
1710 && !is_bucket(next)) {
1711 break;
1712 }
1713 node = clear_flag(next);
1714 }
1715 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1716 iter->node = node;
1717 iter->next = next;
1718 }
1719
1720 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1721 {
1722 cds_lfht_iter_debug_set_ht(ht, iter);
1723 /*
1724 * Get next after first bucket node. The first bucket node is the
1725 * first node of the linked list.
1726 */
1727 iter->next = bucket_at(ht, 0)->next;
1728 cds_lfht_next(ht, iter);
1729 }
1730
1731 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
1732 struct cds_lfht_node *node)
1733 {
1734 unsigned long size;
1735
1736 node->reverse_hash = bit_reverse_ulong(hash);
1737 size = rcu_dereference(ht->size);
1738 _cds_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0);
1739 ht_count_add(ht, size, hash);
1740 }
1741
1742 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
1743 unsigned long hash,
1744 cds_lfht_match_fct match,
1745 const void *key,
1746 struct cds_lfht_node *node)
1747 {
1748 unsigned long size;
1749 struct cds_lfht_iter iter;
1750
1751 node->reverse_hash = bit_reverse_ulong(hash);
1752 size = rcu_dereference(ht->size);
1753 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1754 if (iter.node == node)
1755 ht_count_add(ht, size, hash);
1756 return iter.node;
1757 }
1758
1759 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
1760 unsigned long hash,
1761 cds_lfht_match_fct match,
1762 const void *key,
1763 struct cds_lfht_node *node)
1764 {
1765 unsigned long size;
1766 struct cds_lfht_iter iter;
1767
1768 node->reverse_hash = bit_reverse_ulong(hash);
1769 size = rcu_dereference(ht->size);
1770 for (;;) {
1771 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1772 if (iter.node == node) {
1773 ht_count_add(ht, size, hash);
1774 return NULL;
1775 }
1776
1777 if (!_cds_lfht_replace(ht, size, iter.node, iter.next, node))
1778 return iter.node;
1779 }
1780 }
1781
1782 int cds_lfht_replace(struct cds_lfht *ht,
1783 struct cds_lfht_iter *old_iter,
1784 unsigned long hash,
1785 cds_lfht_match_fct match,
1786 const void *key,
1787 struct cds_lfht_node *new_node)
1788 {
1789 unsigned long size;
1790
1791 new_node->reverse_hash = bit_reverse_ulong(hash);
1792 if (!old_iter->node)
1793 return -ENOENT;
1794 if (caa_unlikely(old_iter->node->reverse_hash != new_node->reverse_hash))
1795 return -EINVAL;
1796 if (caa_unlikely(!match(old_iter->node, key)))
1797 return -EINVAL;
1798 size = rcu_dereference(ht->size);
1799 return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next,
1800 new_node);
1801 }
1802
1803 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
1804 {
1805 unsigned long size;
1806 int ret;
1807
1808 size = rcu_dereference(ht->size);
1809 ret = _cds_lfht_del(ht, size, node);
1810 if (!ret) {
1811 unsigned long hash;
1812
1813 hash = bit_reverse_ulong(node->reverse_hash);
1814 ht_count_del(ht, size, hash);
1815 }
1816 return ret;
1817 }
1818
1819 int cds_lfht_is_node_deleted(struct cds_lfht_node *node)
1820 {
1821 return is_removed(CMM_LOAD_SHARED(node->next));
1822 }
1823
1824 static
1825 int cds_lfht_delete_bucket(struct cds_lfht *ht)
1826 {
1827 struct cds_lfht_node *node;
1828 unsigned long order, i, size;
1829
1830 /* Check that the table is empty */
1831 node = bucket_at(ht, 0);
1832 do {
1833 node = clear_flag(node)->next;
1834 if (!is_bucket(node))
1835 return -EPERM;
1836 assert(!is_removed(node));
1837 assert(!is_removal_owner(node));
1838 } while (!is_end(node));
1839 /*
1840 * size accessed without rcu_dereference because hash table is
1841 * being destroyed.
1842 */
1843 size = ht->size;
1844 /* Internal sanity check: all nodes left should be buckets */
1845 for (i = 0; i < size; i++) {
1846 node = bucket_at(ht, i);
1847 dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
1848 i, i, bit_reverse_ulong(node->reverse_hash));
1849 assert(is_bucket(node->next));
1850 }
1851
1852 for (order = cds_lfht_get_count_order_ulong(size); (long)order >= 0; order--)
1853 cds_lfht_free_bucket_table(ht, order);
1854
1855 return 0;
1856 }
1857
1858 /*
1859 * Should only be called when no more concurrent readers nor writers can
1860 * possibly access the table.
1861 */
1862 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
1863 {
1864 int ret;
1865
1866 if (ht->flags & CDS_LFHT_AUTO_RESIZE) {
1867 /* Cancel ongoing resize operations. */
1868 _CMM_STORE_SHARED(ht->in_progress_destroy, 1);
1869 /* Wait for in-flight resize operations to complete */
1870 urcu_workqueue_flush_queued_work(cds_lfht_workqueue);
1871 }
1872 ret = cds_lfht_delete_bucket(ht);
1873 if (ret)
1874 return ret;
1875 free_split_items_count(ht);
1876 if (attr)
1877 *attr = ht->resize_attr;
1878 ret = pthread_mutex_destroy(&ht->resize_mutex);
1879 if (ret)
1880 ret = -EBUSY;
1881 if (ht->flags & CDS_LFHT_AUTO_RESIZE)
1882 cds_lfht_fini_worker(ht->flavor);
1883 poison_free(ht);
1884 return ret;
1885 }
1886
1887 void cds_lfht_count_nodes(struct cds_lfht *ht,
1888 long *approx_before,
1889 unsigned long *count,
1890 long *approx_after)
1891 {
1892 struct cds_lfht_node *node, *next;
1893 unsigned long nr_bucket = 0, nr_removed = 0;
1894
1895 *approx_before = 0;
1896 if (ht->split_count) {
1897 int i;
1898
1899 for (i = 0; i < split_count_mask + 1; i++) {
1900 *approx_before += uatomic_read(&ht->split_count[i].add);
1901 *approx_before -= uatomic_read(&ht->split_count[i].del);
1902 }
1903 }
1904
1905 *count = 0;
1906
1907 /* Count non-bucket nodes in the table */
1908 node = bucket_at(ht, 0);
1909 do {
1910 next = rcu_dereference(node->next);
1911 if (is_removed(next)) {
1912 if (!is_bucket(next))
1913 (nr_removed)++;
1914 else
1915 (nr_bucket)++;
1916 } else if (!is_bucket(next))
1917 (*count)++;
1918 else
1919 (nr_bucket)++;
1920 node = clear_flag(next);
1921 } while (!is_end(node));
1922 dbg_printf("number of logically removed nodes: %lu\n", nr_removed);
1923 dbg_printf("number of bucket nodes: %lu\n", nr_bucket);
1924 *approx_after = 0;
1925 if (ht->split_count) {
1926 int i;
1927
1928 for (i = 0; i < split_count_mask + 1; i++) {
1929 *approx_after += uatomic_read(&ht->split_count[i].add);
1930 *approx_after -= uatomic_read(&ht->split_count[i].del);
1931 }
1932 }
1933 }
1934
1935 /* called with resize mutex held */
1936 static
1937 void _do_cds_lfht_grow(struct cds_lfht *ht,
1938 unsigned long old_size, unsigned long new_size)
1939 {
1940 unsigned long old_order, new_order;
1941
1942 old_order = cds_lfht_get_count_order_ulong(old_size);
1943 new_order = cds_lfht_get_count_order_ulong(new_size);
1944 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1945 old_size, old_order, new_size, new_order);
1946 assert(new_size > old_size);
1947 init_table(ht, old_order + 1, new_order);
1948 }
1949
1950 /* called with resize mutex held */
1951 static
1952 void _do_cds_lfht_shrink(struct cds_lfht *ht,
1953 unsigned long old_size, unsigned long new_size)
1954 {
1955 unsigned long old_order, new_order;
1956
1957 new_size = max(new_size, MIN_TABLE_SIZE);
1958 old_order = cds_lfht_get_count_order_ulong(old_size);
1959 new_order = cds_lfht_get_count_order_ulong(new_size);
1960 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1961 old_size, old_order, new_size, new_order);
1962 assert(new_size < old_size);
1963
1964 /* Remove and unlink all bucket nodes to remove. */
1965 fini_table(ht, new_order + 1, old_order);
1966 }
1967
1968
1969 /* called with resize mutex held */
1970 static
1971 void _do_cds_lfht_resize(struct cds_lfht *ht)
1972 {
1973 unsigned long new_size, old_size;
1974
1975 /*
1976 * Resize table, re-do if the target size has changed under us.
1977 */
1978 do {
1979 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1980 break;
1981 ht->resize_initiated = 1;
1982 old_size = ht->size;
1983 new_size = CMM_LOAD_SHARED(ht->resize_target);
1984 if (old_size < new_size)
1985 _do_cds_lfht_grow(ht, old_size, new_size);
1986 else if (old_size > new_size)
1987 _do_cds_lfht_shrink(ht, old_size, new_size);
1988 ht->resize_initiated = 0;
1989 /* write resize_initiated before read resize_target */
1990 cmm_smp_mb();
1991 } while (ht->size != CMM_LOAD_SHARED(ht->resize_target));
1992 }
1993
1994 static
1995 unsigned long resize_target_grow(struct cds_lfht *ht, unsigned long new_size)
1996 {
1997 return _uatomic_xchg_monotonic_increase(&ht->resize_target, new_size);
1998 }
1999
2000 static
2001 void resize_target_update_count(struct cds_lfht *ht,
2002 unsigned long count)
2003 {
2004 count = max(count, MIN_TABLE_SIZE);
2005 count = min(count, ht->max_nr_buckets);
2006 uatomic_set(&ht->resize_target, count);
2007 }
2008
2009 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
2010 {
2011 resize_target_update_count(ht, new_size);
2012 CMM_STORE_SHARED(ht->resize_initiated, 1);
2013 mutex_lock(&ht->resize_mutex);
2014 _do_cds_lfht_resize(ht);
2015 mutex_unlock(&ht->resize_mutex);
2016 }
2017
2018 static
2019 void do_resize_cb(struct urcu_work *work)
2020 {
2021 struct resize_work *resize_work =
2022 caa_container_of(work, struct resize_work, work);
2023 struct cds_lfht *ht = resize_work->ht;
2024
2025 ht->flavor->register_thread();
2026 mutex_lock(&ht->resize_mutex);
2027 _do_cds_lfht_resize(ht);
2028 mutex_unlock(&ht->resize_mutex);
2029 ht->flavor->unregister_thread();
2030 poison_free(work);
2031 }
2032
2033 static
2034 void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht)
2035 {
2036 struct resize_work *work;
2037
2038 /* Store resize_target before read resize_initiated */
2039 cmm_smp_mb();
2040 if (!CMM_LOAD_SHARED(ht->resize_initiated)) {
2041 if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
2042 return;
2043 }
2044 work = malloc(sizeof(*work));
2045 if (work == NULL) {
2046 dbg_printf("error allocating resize work, bailing out\n");
2047 return;
2048 }
2049 work->ht = ht;
2050 urcu_workqueue_queue_work(cds_lfht_workqueue,
2051 &work->work, do_resize_cb);
2052 CMM_STORE_SHARED(ht->resize_initiated, 1);
2053 }
2054 }
2055
2056 static
2057 void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
2058 {
2059 unsigned long target_size = size << growth;
2060
2061 target_size = min(target_size, ht->max_nr_buckets);
2062 if (resize_target_grow(ht, target_size) >= target_size)
2063 return;
2064
2065 __cds_lfht_resize_lazy_launch(ht);
2066 }
2067
2068 /*
2069 * We favor grow operations over shrink. A shrink operation never occurs
2070 * if a grow operation is queued for lazy execution. A grow operation
2071 * cancels any pending shrink lazy execution.
2072 */
2073 static
2074 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
2075 unsigned long count)
2076 {
2077 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
2078 return;
2079 count = max(count, MIN_TABLE_SIZE);
2080 count = min(count, ht->max_nr_buckets);
2081 if (count == size)
2082 return; /* Already the right size, no resize needed */
2083 if (count > size) { /* lazy grow */
2084 if (resize_target_grow(ht, count) >= count)
2085 return;
2086 } else { /* lazy shrink */
2087 for (;;) {
2088 unsigned long s;
2089
2090 s = uatomic_cmpxchg(&ht->resize_target, size, count);
2091 if (s == size)
2092 break; /* no resize needed */
2093 if (s > size)
2094 return; /* growing is/(was just) in progress */
2095 if (s <= count)
2096 return; /* some other thread do shrink */
2097 size = s;
2098 }
2099 }
2100 __cds_lfht_resize_lazy_launch(ht);
2101 }
2102
2103 static void cds_lfht_before_fork(void *priv)
2104 {
2105 if (cds_lfht_workqueue_atfork_nesting++)
2106 return;
2107 mutex_lock(&cds_lfht_fork_mutex);
2108 if (!cds_lfht_workqueue)
2109 return;
2110 urcu_workqueue_pause_worker(cds_lfht_workqueue);
2111 }
2112
2113 static void cds_lfht_after_fork_parent(void *priv)
2114 {
2115 if (--cds_lfht_workqueue_atfork_nesting)
2116 return;
2117 if (!cds_lfht_workqueue)
2118 goto end;
2119 urcu_workqueue_resume_worker(cds_lfht_workqueue);
2120 end:
2121 mutex_unlock(&cds_lfht_fork_mutex);
2122 }
2123
2124 static void cds_lfht_after_fork_child(void *priv)
2125 {
2126 if (--cds_lfht_workqueue_atfork_nesting)
2127 return;
2128 if (!cds_lfht_workqueue)
2129 goto end;
2130 urcu_workqueue_create_worker(cds_lfht_workqueue);
2131 end:
2132 mutex_unlock(&cds_lfht_fork_mutex);
2133 }
2134
2135 static struct urcu_atfork cds_lfht_atfork = {
2136 .before_fork = cds_lfht_before_fork,
2137 .after_fork_parent = cds_lfht_after_fork_parent,
2138 .after_fork_child = cds_lfht_after_fork_child,
2139 };
2140
2141 /* Block all signals to ensure we don't disturb the application. */
2142 static void cds_lfht_worker_init(struct urcu_workqueue *workqueue,
2143 void *priv)
2144 {
2145 int ret;
2146 sigset_t mask;
2147
2148 /* Block signal for entire process, so only our thread processes it. */
2149 ret = sigfillset(&mask);
2150 if (ret)
2151 urcu_die(errno);
2152 ret = pthread_sigmask(SIG_BLOCK, &mask, NULL);
2153 if (ret)
2154 urcu_die(ret);
2155 }
2156
2157 static void cds_lfht_init_worker(const struct rcu_flavor_struct *flavor)
2158 {
2159 flavor->register_rculfhash_atfork(&cds_lfht_atfork);
2160
2161 mutex_lock(&cds_lfht_fork_mutex);
2162 if (cds_lfht_workqueue_user_count++)
2163 goto end;
2164 cds_lfht_workqueue = urcu_workqueue_create(0, -1, NULL,
2165 NULL, cds_lfht_worker_init, NULL, NULL, NULL, NULL, NULL);
2166 end:
2167 mutex_unlock(&cds_lfht_fork_mutex);
2168 }
2169
2170 static void cds_lfht_fini_worker(const struct rcu_flavor_struct *flavor)
2171 {
2172 mutex_lock(&cds_lfht_fork_mutex);
2173 if (--cds_lfht_workqueue_user_count)
2174 goto end;
2175 urcu_workqueue_destroy(cds_lfht_workqueue);
2176 cds_lfht_workqueue = NULL;
2177 end:
2178 mutex_unlock(&cds_lfht_fork_mutex);
2179
2180 flavor->unregister_rculfhash_atfork(&cds_lfht_atfork);
2181 }
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