e0c5860c7b6b91e448b68b250c5c0a58afd49825
[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 #if (CAA_BITS_PER_LONG > 32)
1547 /*
1548 * For 64-bit architectures, with max number of buckets small enough not to
1549 * use the entire 64-bit memory mapping space (and allowing a fair number of
1550 * hash table instances), use the mmap allocator, which is faster. Otherwise,
1551 * fallback to the order allocator.
1552 */
1553 static
1554 const struct cds_lfht_mm_type *get_mm_type(unsigned long max_nr_buckets)
1555 {
1556 if (max_nr_buckets && max_nr_buckets <= (1ULL << 32))
1557 return &cds_lfht_mm_mmap;
1558 else
1559 return &cds_lfht_mm_order;
1560 }
1561 #else
1562 /*
1563 * For 32-bit architectures, use the order allocator.
1564 */
1565 static
1566 const struct cds_lfht_mm_type *get_mm_type(unsigned long max_nr_buckets)
1567 {
1568 return &cds_lfht_mm_order;
1569 }
1570 #endif
1571
1572 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
1573 unsigned long min_nr_alloc_buckets,
1574 unsigned long max_nr_buckets,
1575 int flags,
1576 const struct cds_lfht_mm_type *mm,
1577 const struct rcu_flavor_struct *flavor,
1578 pthread_attr_t *attr)
1579 {
1580 struct cds_lfht *ht;
1581 unsigned long order;
1582
1583 /* min_nr_alloc_buckets must be power of two */
1584 if (!min_nr_alloc_buckets || (min_nr_alloc_buckets & (min_nr_alloc_buckets - 1)))
1585 return NULL;
1586
1587 /* init_size must be power of two */
1588 if (!init_size || (init_size & (init_size - 1)))
1589 return NULL;
1590
1591 /*
1592 * Memory management plugin default.
1593 */
1594 if (!mm)
1595 mm = get_mm_type(max_nr_buckets);
1596
1597 /* max_nr_buckets == 0 for order based mm means infinite */
1598 if (mm == &cds_lfht_mm_order && !max_nr_buckets)
1599 max_nr_buckets = 1UL << (MAX_TABLE_ORDER - 1);
1600
1601 /* max_nr_buckets must be power of two */
1602 if (!max_nr_buckets || (max_nr_buckets & (max_nr_buckets - 1)))
1603 return NULL;
1604
1605 if (flags & CDS_LFHT_AUTO_RESIZE)
1606 cds_lfht_init_worker(flavor);
1607
1608 min_nr_alloc_buckets = max(min_nr_alloc_buckets, MIN_TABLE_SIZE);
1609 init_size = max(init_size, MIN_TABLE_SIZE);
1610 max_nr_buckets = max(max_nr_buckets, min_nr_alloc_buckets);
1611 init_size = min(init_size, max_nr_buckets);
1612
1613 ht = mm->alloc_cds_lfht(min_nr_alloc_buckets, max_nr_buckets);
1614 assert(ht);
1615 assert(ht->mm == mm);
1616 assert(ht->bucket_at == mm->bucket_at);
1617
1618 ht->flags = flags;
1619 ht->flavor = flavor;
1620 ht->resize_attr = attr;
1621 alloc_split_items_count(ht);
1622 /* this mutex should not nest in read-side C.S. */
1623 pthread_mutex_init(&ht->resize_mutex, NULL);
1624 order = cds_lfht_get_count_order_ulong(init_size);
1625 ht->resize_target = 1UL << order;
1626 cds_lfht_create_bucket(ht, 1UL << order);
1627 ht->size = 1UL << order;
1628 return ht;
1629 }
1630
1631 void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
1632 cds_lfht_match_fct match, const void *key,
1633 struct cds_lfht_iter *iter)
1634 {
1635 struct cds_lfht_node *node, *next, *bucket;
1636 unsigned long reverse_hash, size;
1637
1638 cds_lfht_iter_debug_set_ht(ht, iter);
1639
1640 reverse_hash = bit_reverse_ulong(hash);
1641
1642 size = rcu_dereference(ht->size);
1643 bucket = lookup_bucket(ht, size, hash);
1644 /* We can always skip the bucket node initially */
1645 node = rcu_dereference(bucket->next);
1646 node = clear_flag(node);
1647 for (;;) {
1648 if (caa_unlikely(is_end(node))) {
1649 node = next = NULL;
1650 break;
1651 }
1652 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1653 node = next = NULL;
1654 break;
1655 }
1656 next = rcu_dereference(node->next);
1657 assert(node == clear_flag(node));
1658 if (caa_likely(!is_removed(next))
1659 && !is_bucket(next)
1660 && node->reverse_hash == reverse_hash
1661 && caa_likely(match(node, key))) {
1662 break;
1663 }
1664 node = clear_flag(next);
1665 }
1666 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1667 iter->node = node;
1668 iter->next = next;
1669 }
1670
1671 void cds_lfht_next_duplicate(struct cds_lfht *ht, cds_lfht_match_fct match,
1672 const void *key, struct cds_lfht_iter *iter)
1673 {
1674 struct cds_lfht_node *node, *next;
1675 unsigned long reverse_hash;
1676
1677 cds_lfht_iter_debug_assert(ht == iter->lfht);
1678 node = iter->node;
1679 reverse_hash = node->reverse_hash;
1680 next = iter->next;
1681 node = clear_flag(next);
1682
1683 for (;;) {
1684 if (caa_unlikely(is_end(node))) {
1685 node = next = NULL;
1686 break;
1687 }
1688 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1689 node = next = NULL;
1690 break;
1691 }
1692 next = rcu_dereference(node->next);
1693 if (caa_likely(!is_removed(next))
1694 && !is_bucket(next)
1695 && caa_likely(match(node, key))) {
1696 break;
1697 }
1698 node = clear_flag(next);
1699 }
1700 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1701 iter->node = node;
1702 iter->next = next;
1703 }
1704
1705 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1706 {
1707 struct cds_lfht_node *node, *next;
1708
1709 cds_lfht_iter_debug_assert(ht == iter->lfht);
1710 node = clear_flag(iter->next);
1711 for (;;) {
1712 if (caa_unlikely(is_end(node))) {
1713 node = next = NULL;
1714 break;
1715 }
1716 next = rcu_dereference(node->next);
1717 if (caa_likely(!is_removed(next))
1718 && !is_bucket(next)) {
1719 break;
1720 }
1721 node = clear_flag(next);
1722 }
1723 assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1724 iter->node = node;
1725 iter->next = next;
1726 }
1727
1728 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1729 {
1730 cds_lfht_iter_debug_set_ht(ht, iter);
1731 /*
1732 * Get next after first bucket node. The first bucket node is the
1733 * first node of the linked list.
1734 */
1735 iter->next = bucket_at(ht, 0)->next;
1736 cds_lfht_next(ht, iter);
1737 }
1738
1739 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
1740 struct cds_lfht_node *node)
1741 {
1742 unsigned long size;
1743
1744 node->reverse_hash = bit_reverse_ulong(hash);
1745 size = rcu_dereference(ht->size);
1746 _cds_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0);
1747 ht_count_add(ht, size, hash);
1748 }
1749
1750 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
1751 unsigned long hash,
1752 cds_lfht_match_fct match,
1753 const void *key,
1754 struct cds_lfht_node *node)
1755 {
1756 unsigned long size;
1757 struct cds_lfht_iter iter;
1758
1759 node->reverse_hash = bit_reverse_ulong(hash);
1760 size = rcu_dereference(ht->size);
1761 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1762 if (iter.node == node)
1763 ht_count_add(ht, size, hash);
1764 return iter.node;
1765 }
1766
1767 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
1768 unsigned long hash,
1769 cds_lfht_match_fct match,
1770 const void *key,
1771 struct cds_lfht_node *node)
1772 {
1773 unsigned long size;
1774 struct cds_lfht_iter iter;
1775
1776 node->reverse_hash = bit_reverse_ulong(hash);
1777 size = rcu_dereference(ht->size);
1778 for (;;) {
1779 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1780 if (iter.node == node) {
1781 ht_count_add(ht, size, hash);
1782 return NULL;
1783 }
1784
1785 if (!_cds_lfht_replace(ht, size, iter.node, iter.next, node))
1786 return iter.node;
1787 }
1788 }
1789
1790 int cds_lfht_replace(struct cds_lfht *ht,
1791 struct cds_lfht_iter *old_iter,
1792 unsigned long hash,
1793 cds_lfht_match_fct match,
1794 const void *key,
1795 struct cds_lfht_node *new_node)
1796 {
1797 unsigned long size;
1798
1799 new_node->reverse_hash = bit_reverse_ulong(hash);
1800 if (!old_iter->node)
1801 return -ENOENT;
1802 if (caa_unlikely(old_iter->node->reverse_hash != new_node->reverse_hash))
1803 return -EINVAL;
1804 if (caa_unlikely(!match(old_iter->node, key)))
1805 return -EINVAL;
1806 size = rcu_dereference(ht->size);
1807 return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next,
1808 new_node);
1809 }
1810
1811 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
1812 {
1813 unsigned long size;
1814 int ret;
1815
1816 size = rcu_dereference(ht->size);
1817 ret = _cds_lfht_del(ht, size, node);
1818 if (!ret) {
1819 unsigned long hash;
1820
1821 hash = bit_reverse_ulong(node->reverse_hash);
1822 ht_count_del(ht, size, hash);
1823 }
1824 return ret;
1825 }
1826
1827 int cds_lfht_is_node_deleted(struct cds_lfht_node *node)
1828 {
1829 return is_removed(CMM_LOAD_SHARED(node->next));
1830 }
1831
1832 static
1833 int cds_lfht_delete_bucket(struct cds_lfht *ht)
1834 {
1835 struct cds_lfht_node *node;
1836 unsigned long order, i, size;
1837
1838 /* Check that the table is empty */
1839 node = bucket_at(ht, 0);
1840 do {
1841 node = clear_flag(node)->next;
1842 if (!is_bucket(node))
1843 return -EPERM;
1844 assert(!is_removed(node));
1845 assert(!is_removal_owner(node));
1846 } while (!is_end(node));
1847 /*
1848 * size accessed without rcu_dereference because hash table is
1849 * being destroyed.
1850 */
1851 size = ht->size;
1852 /* Internal sanity check: all nodes left should be buckets */
1853 for (i = 0; i < size; i++) {
1854 node = bucket_at(ht, i);
1855 dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
1856 i, i, bit_reverse_ulong(node->reverse_hash));
1857 assert(is_bucket(node->next));
1858 }
1859
1860 for (order = cds_lfht_get_count_order_ulong(size); (long)order >= 0; order--)
1861 cds_lfht_free_bucket_table(ht, order);
1862
1863 return 0;
1864 }
1865
1866 /*
1867 * Should only be called when no more concurrent readers nor writers can
1868 * possibly access the table.
1869 */
1870 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
1871 {
1872 int ret;
1873
1874 if (ht->flags & CDS_LFHT_AUTO_RESIZE) {
1875 /* Cancel ongoing resize operations. */
1876 _CMM_STORE_SHARED(ht->in_progress_destroy, 1);
1877 /* Wait for in-flight resize operations to complete */
1878 urcu_workqueue_flush_queued_work(cds_lfht_workqueue);
1879 }
1880 ret = cds_lfht_delete_bucket(ht);
1881 if (ret)
1882 return ret;
1883 free_split_items_count(ht);
1884 if (attr)
1885 *attr = ht->resize_attr;
1886 ret = pthread_mutex_destroy(&ht->resize_mutex);
1887 if (ret)
1888 ret = -EBUSY;
1889 if (ht->flags & CDS_LFHT_AUTO_RESIZE)
1890 cds_lfht_fini_worker(ht->flavor);
1891 poison_free(ht);
1892 return ret;
1893 }
1894
1895 void cds_lfht_count_nodes(struct cds_lfht *ht,
1896 long *approx_before,
1897 unsigned long *count,
1898 long *approx_after)
1899 {
1900 struct cds_lfht_node *node, *next;
1901 unsigned long nr_bucket = 0, nr_removed = 0;
1902
1903 *approx_before = 0;
1904 if (ht->split_count) {
1905 int i;
1906
1907 for (i = 0; i < split_count_mask + 1; i++) {
1908 *approx_before += uatomic_read(&ht->split_count[i].add);
1909 *approx_before -= uatomic_read(&ht->split_count[i].del);
1910 }
1911 }
1912
1913 *count = 0;
1914
1915 /* Count non-bucket nodes in the table */
1916 node = bucket_at(ht, 0);
1917 do {
1918 next = rcu_dereference(node->next);
1919 if (is_removed(next)) {
1920 if (!is_bucket(next))
1921 (nr_removed)++;
1922 else
1923 (nr_bucket)++;
1924 } else if (!is_bucket(next))
1925 (*count)++;
1926 else
1927 (nr_bucket)++;
1928 node = clear_flag(next);
1929 } while (!is_end(node));
1930 dbg_printf("number of logically removed nodes: %lu\n", nr_removed);
1931 dbg_printf("number of bucket nodes: %lu\n", nr_bucket);
1932 *approx_after = 0;
1933 if (ht->split_count) {
1934 int i;
1935
1936 for (i = 0; i < split_count_mask + 1; i++) {
1937 *approx_after += uatomic_read(&ht->split_count[i].add);
1938 *approx_after -= uatomic_read(&ht->split_count[i].del);
1939 }
1940 }
1941 }
1942
1943 /* called with resize mutex held */
1944 static
1945 void _do_cds_lfht_grow(struct cds_lfht *ht,
1946 unsigned long old_size, unsigned long new_size)
1947 {
1948 unsigned long old_order, new_order;
1949
1950 old_order = cds_lfht_get_count_order_ulong(old_size);
1951 new_order = cds_lfht_get_count_order_ulong(new_size);
1952 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1953 old_size, old_order, new_size, new_order);
1954 assert(new_size > old_size);
1955 init_table(ht, old_order + 1, new_order);
1956 }
1957
1958 /* called with resize mutex held */
1959 static
1960 void _do_cds_lfht_shrink(struct cds_lfht *ht,
1961 unsigned long old_size, unsigned long new_size)
1962 {
1963 unsigned long old_order, new_order;
1964
1965 new_size = max(new_size, MIN_TABLE_SIZE);
1966 old_order = cds_lfht_get_count_order_ulong(old_size);
1967 new_order = cds_lfht_get_count_order_ulong(new_size);
1968 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1969 old_size, old_order, new_size, new_order);
1970 assert(new_size < old_size);
1971
1972 /* Remove and unlink all bucket nodes to remove. */
1973 fini_table(ht, new_order + 1, old_order);
1974 }
1975
1976
1977 /* called with resize mutex held */
1978 static
1979 void _do_cds_lfht_resize(struct cds_lfht *ht)
1980 {
1981 unsigned long new_size, old_size;
1982
1983 /*
1984 * Resize table, re-do if the target size has changed under us.
1985 */
1986 do {
1987 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1988 break;
1989 ht->resize_initiated = 1;
1990 old_size = ht->size;
1991 new_size = CMM_LOAD_SHARED(ht->resize_target);
1992 if (old_size < new_size)
1993 _do_cds_lfht_grow(ht, old_size, new_size);
1994 else if (old_size > new_size)
1995 _do_cds_lfht_shrink(ht, old_size, new_size);
1996 ht->resize_initiated = 0;
1997 /* write resize_initiated before read resize_target */
1998 cmm_smp_mb();
1999 } while (ht->size != CMM_LOAD_SHARED(ht->resize_target));
2000 }
2001
2002 static
2003 unsigned long resize_target_grow(struct cds_lfht *ht, unsigned long new_size)
2004 {
2005 return _uatomic_xchg_monotonic_increase(&ht->resize_target, new_size);
2006 }
2007
2008 static
2009 void resize_target_update_count(struct cds_lfht *ht,
2010 unsigned long count)
2011 {
2012 count = max(count, MIN_TABLE_SIZE);
2013 count = min(count, ht->max_nr_buckets);
2014 uatomic_set(&ht->resize_target, count);
2015 }
2016
2017 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
2018 {
2019 resize_target_update_count(ht, new_size);
2020 CMM_STORE_SHARED(ht->resize_initiated, 1);
2021 mutex_lock(&ht->resize_mutex);
2022 _do_cds_lfht_resize(ht);
2023 mutex_unlock(&ht->resize_mutex);
2024 }
2025
2026 static
2027 void do_resize_cb(struct urcu_work *work)
2028 {
2029 struct resize_work *resize_work =
2030 caa_container_of(work, struct resize_work, work);
2031 struct cds_lfht *ht = resize_work->ht;
2032
2033 ht->flavor->register_thread();
2034 mutex_lock(&ht->resize_mutex);
2035 _do_cds_lfht_resize(ht);
2036 mutex_unlock(&ht->resize_mutex);
2037 ht->flavor->unregister_thread();
2038 poison_free(work);
2039 }
2040
2041 static
2042 void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht)
2043 {
2044 struct resize_work *work;
2045
2046 /* Store resize_target before read resize_initiated */
2047 cmm_smp_mb();
2048 if (!CMM_LOAD_SHARED(ht->resize_initiated)) {
2049 if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
2050 return;
2051 }
2052 work = malloc(sizeof(*work));
2053 if (work == NULL) {
2054 dbg_printf("error allocating resize work, bailing out\n");
2055 return;
2056 }
2057 work->ht = ht;
2058 urcu_workqueue_queue_work(cds_lfht_workqueue,
2059 &work->work, do_resize_cb);
2060 CMM_STORE_SHARED(ht->resize_initiated, 1);
2061 }
2062 }
2063
2064 static
2065 void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
2066 {
2067 unsigned long target_size = size << growth;
2068
2069 target_size = min(target_size, ht->max_nr_buckets);
2070 if (resize_target_grow(ht, target_size) >= target_size)
2071 return;
2072
2073 __cds_lfht_resize_lazy_launch(ht);
2074 }
2075
2076 /*
2077 * We favor grow operations over shrink. A shrink operation never occurs
2078 * if a grow operation is queued for lazy execution. A grow operation
2079 * cancels any pending shrink lazy execution.
2080 */
2081 static
2082 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
2083 unsigned long count)
2084 {
2085 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
2086 return;
2087 count = max(count, MIN_TABLE_SIZE);
2088 count = min(count, ht->max_nr_buckets);
2089 if (count == size)
2090 return; /* Already the right size, no resize needed */
2091 if (count > size) { /* lazy grow */
2092 if (resize_target_grow(ht, count) >= count)
2093 return;
2094 } else { /* lazy shrink */
2095 for (;;) {
2096 unsigned long s;
2097
2098 s = uatomic_cmpxchg(&ht->resize_target, size, count);
2099 if (s == size)
2100 break; /* no resize needed */
2101 if (s > size)
2102 return; /* growing is/(was just) in progress */
2103 if (s <= count)
2104 return; /* some other thread do shrink */
2105 size = s;
2106 }
2107 }
2108 __cds_lfht_resize_lazy_launch(ht);
2109 }
2110
2111 static void cds_lfht_before_fork(void *priv)
2112 {
2113 if (cds_lfht_workqueue_atfork_nesting++)
2114 return;
2115 mutex_lock(&cds_lfht_fork_mutex);
2116 if (!cds_lfht_workqueue)
2117 return;
2118 urcu_workqueue_pause_worker(cds_lfht_workqueue);
2119 }
2120
2121 static void cds_lfht_after_fork_parent(void *priv)
2122 {
2123 if (--cds_lfht_workqueue_atfork_nesting)
2124 return;
2125 if (!cds_lfht_workqueue)
2126 goto end;
2127 urcu_workqueue_resume_worker(cds_lfht_workqueue);
2128 end:
2129 mutex_unlock(&cds_lfht_fork_mutex);
2130 }
2131
2132 static void cds_lfht_after_fork_child(void *priv)
2133 {
2134 if (--cds_lfht_workqueue_atfork_nesting)
2135 return;
2136 if (!cds_lfht_workqueue)
2137 goto end;
2138 urcu_workqueue_create_worker(cds_lfht_workqueue);
2139 end:
2140 mutex_unlock(&cds_lfht_fork_mutex);
2141 }
2142
2143 static struct urcu_atfork cds_lfht_atfork = {
2144 .before_fork = cds_lfht_before_fork,
2145 .after_fork_parent = cds_lfht_after_fork_parent,
2146 .after_fork_child = cds_lfht_after_fork_child,
2147 };
2148
2149 /* Block all signals to ensure we don't disturb the application. */
2150 static void cds_lfht_worker_init(struct urcu_workqueue *workqueue,
2151 void *priv)
2152 {
2153 int ret;
2154 sigset_t mask;
2155
2156 /* Block signal for entire process, so only our thread processes it. */
2157 ret = sigfillset(&mask);
2158 if (ret)
2159 urcu_die(errno);
2160 ret = pthread_sigmask(SIG_BLOCK, &mask, NULL);
2161 if (ret)
2162 urcu_die(ret);
2163 }
2164
2165 static void cds_lfht_init_worker(const struct rcu_flavor_struct *flavor)
2166 {
2167 flavor->register_rculfhash_atfork(&cds_lfht_atfork);
2168
2169 mutex_lock(&cds_lfht_fork_mutex);
2170 if (cds_lfht_workqueue_user_count++)
2171 goto end;
2172 cds_lfht_workqueue = urcu_workqueue_create(0, -1, NULL,
2173 NULL, cds_lfht_worker_init, NULL, NULL, NULL, NULL, NULL);
2174 end:
2175 mutex_unlock(&cds_lfht_fork_mutex);
2176 }
2177
2178 static void cds_lfht_fini_worker(const struct rcu_flavor_struct *flavor)
2179 {
2180 mutex_lock(&cds_lfht_fork_mutex);
2181 if (--cds_lfht_workqueue_user_count)
2182 goto end;
2183 urcu_workqueue_destroy(cds_lfht_workqueue);
2184 cds_lfht_workqueue = NULL;
2185 end:
2186 mutex_unlock(&cds_lfht_fork_mutex);
2187
2188 flavor->unregister_rculfhash_atfork(&cds_lfht_atfork);
2189 }
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