5391d28e923a0a9b44909f3b8711692f36f4edbf
[userspace-rcu.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 <stdio.h>
262 #include <stdint.h>
263 #include <string.h>
264 #include <sched.h>
265 #include <unistd.h>
266
267 #include "compat-getcpu.h"
268 #include <urcu/assert.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 <urcu/static/urcu-signal-nr.h>
277 #include <stdio.h>
278 #include <pthread.h>
279 #include <signal.h>
280 #include "rculfhash-internal.h"
281 #include "workqueue.h"
282 #include "urcu-die.h"
283 #include "urcu-utils.h"
284 #include "compat-smp.h"
285
286 /*
287 * Split-counters lazily update the global counter each 1024
288 * addition/removal. It automatically keeps track of resize required.
289 * We use the bucket length as indicator for need to expand for small
290 * tables and machines lacking per-cpu data support.
291 */
292 #define COUNT_COMMIT_ORDER 10
293 #define DEFAULT_SPLIT_COUNT_MASK 0xFUL
294 #define CHAIN_LEN_TARGET 1
295 #define CHAIN_LEN_RESIZE_THRESHOLD 3
296
297 /*
298 * Define the minimum table size.
299 */
300 #define MIN_TABLE_ORDER 0
301 #define MIN_TABLE_SIZE (1UL << MIN_TABLE_ORDER)
302
303 /*
304 * Minimum number of bucket nodes to touch per thread to parallelize grow/shrink.
305 */
306 #define MIN_PARTITION_PER_THREAD_ORDER 12
307 #define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
308
309 /*
310 * The removed flag needs to be updated atomically with the pointer.
311 * It indicates that no node must attach to the node scheduled for
312 * removal, and that node garbage collection must be performed.
313 * The bucket flag does not require to be updated atomically with the
314 * pointer, but it is added as a pointer low bit flag to save space.
315 * The "removal owner" flag is used to detect which of the "del"
316 * operation that has set the "removed flag" gets to return the removed
317 * node to its caller. Note that the replace operation does not need to
318 * iteract with the "removal owner" flag, because it validates that
319 * the "removed" flag is not set before performing its cmpxchg.
320 */
321 #define REMOVED_FLAG (1UL << 0)
322 #define BUCKET_FLAG (1UL << 1)
323 #define REMOVAL_OWNER_FLAG (1UL << 2)
324 #define FLAGS_MASK ((1UL << 3) - 1)
325
326 /* Value of the end pointer. Should not interact with flags. */
327 #define END_VALUE NULL
328
329 /*
330 * ht_items_count: Split-counters counting the number of node addition
331 * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
332 * is set at hash table creation.
333 *
334 * These are free-running counters, never reset to zero. They count the
335 * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
336 * operations to update the global counter. We choose a power-of-2 value
337 * for the trigger to deal with 32 or 64-bit overflow of the counter.
338 */
339 struct ht_items_count {
340 unsigned long add, del;
341 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
342
343 /*
344 * resize_work: Contains arguments passed to worker thread
345 * responsible for performing lazy resize.
346 */
347 struct resize_work {
348 struct urcu_work work;
349 struct cds_lfht *ht;
350 };
351
352 /*
353 * partition_resize_work: Contains arguments passed to worker threads
354 * executing the hash table resize on partitions of the hash table
355 * assigned to each processor's worker thread.
356 */
357 struct partition_resize_work {
358 pthread_t thread_id;
359 struct cds_lfht *ht;
360 unsigned long i, start, len;
361 void (*fct)(struct cds_lfht *ht, unsigned long i,
362 unsigned long start, unsigned long len);
363 };
364
365 static struct urcu_workqueue *cds_lfht_workqueue;
366 static unsigned long cds_lfht_workqueue_user_count;
367
368 /*
369 * Mutex ensuring mutual exclusion between workqueue initialization and
370 * fork handlers. cds_lfht_fork_mutex nests inside call_rcu_mutex.
371 */
372 static pthread_mutex_t cds_lfht_fork_mutex = PTHREAD_MUTEX_INITIALIZER;
373
374 static struct urcu_atfork cds_lfht_atfork;
375
376 /*
377 * atfork handler nesting counters. Handle being registered to many urcu
378 * flavors, thus being possibly invoked more than once in the
379 * pthread_atfork list of callbacks.
380 */
381 static int cds_lfht_workqueue_atfork_nesting;
382
383 static void cds_lfht_init_worker(const struct rcu_flavor_struct *flavor);
384 static void cds_lfht_fini_worker(const struct rcu_flavor_struct *flavor);
385
386 #ifdef CONFIG_CDS_LFHT_ITER_DEBUG
387
388 static
389 void cds_lfht_iter_debug_set_ht(struct cds_lfht *ht, struct cds_lfht_iter *iter)
390 {
391 iter->lfht = ht;
392 }
393
394 #define cds_lfht_iter_debug_assert(...) urcu_posix_assert(__VA_ARGS__)
395
396 #else
397
398 static
399 void cds_lfht_iter_debug_set_ht(struct cds_lfht *ht __attribute__((unused)),
400 struct cds_lfht_iter *iter __attribute__((unused)))
401 {
402 }
403
404 #define cds_lfht_iter_debug_assert(...)
405
406 #endif
407
408 /*
409 * Algorithm to reverse bits in a word by lookup table, extended to
410 * 64-bit words.
411 * Source:
412 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
413 * Originally from Public Domain.
414 */
415
416 static const uint8_t BitReverseTable256[256] =
417 {
418 #define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
419 #define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
420 #define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
421 R6(0), R6(2), R6(1), R6(3)
422 };
423 #undef R2
424 #undef R4
425 #undef R6
426
427 static
428 uint8_t bit_reverse_u8(uint8_t v)
429 {
430 return BitReverseTable256[v];
431 }
432
433 #if (CAA_BITS_PER_LONG == 32)
434 static
435 uint32_t bit_reverse_u32(uint32_t v)
436 {
437 return ((uint32_t) bit_reverse_u8(v) << 24) |
438 ((uint32_t) bit_reverse_u8(v >> 8) << 16) |
439 ((uint32_t) bit_reverse_u8(v >> 16) << 8) |
440 ((uint32_t) bit_reverse_u8(v >> 24));
441 }
442 #else
443 static
444 uint64_t bit_reverse_u64(uint64_t v)
445 {
446 return ((uint64_t) bit_reverse_u8(v) << 56) |
447 ((uint64_t) bit_reverse_u8(v >> 8) << 48) |
448 ((uint64_t) bit_reverse_u8(v >> 16) << 40) |
449 ((uint64_t) bit_reverse_u8(v >> 24) << 32) |
450 ((uint64_t) bit_reverse_u8(v >> 32) << 24) |
451 ((uint64_t) bit_reverse_u8(v >> 40) << 16) |
452 ((uint64_t) bit_reverse_u8(v >> 48) << 8) |
453 ((uint64_t) bit_reverse_u8(v >> 56));
454 }
455 #endif
456
457 static
458 unsigned long bit_reverse_ulong(unsigned long v)
459 {
460 #if (CAA_BITS_PER_LONG == 32)
461 return bit_reverse_u32(v);
462 #else
463 return bit_reverse_u64(v);
464 #endif
465 }
466
467 /*
468 * fls: returns the position of the most significant bit.
469 * Returns 0 if no bit is set, else returns the position of the most
470 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
471 */
472 #if defined(URCU_ARCH_X86)
473 static inline
474 unsigned int fls_u32(uint32_t x)
475 {
476 int r;
477
478 __asm__ ("bsrl %1,%0\n\t"
479 "jnz 1f\n\t"
480 "movl $-1,%0\n\t"
481 "1:\n\t"
482 : "=r" (r) : "rm" (x));
483 return r + 1;
484 }
485 #define HAS_FLS_U32
486 #endif
487
488 #if defined(URCU_ARCH_AMD64)
489 static inline
490 unsigned int fls_u64(uint64_t x)
491 {
492 long r;
493
494 __asm__ ("bsrq %1,%0\n\t"
495 "jnz 1f\n\t"
496 "movq $-1,%0\n\t"
497 "1:\n\t"
498 : "=r" (r) : "rm" (x));
499 return r + 1;
500 }
501 #define HAS_FLS_U64
502 #endif
503
504 #ifndef HAS_FLS_U64
505 static __attribute__((unused))
506 unsigned int fls_u64(uint64_t x)
507 {
508 unsigned int r = 64;
509
510 if (!x)
511 return 0;
512
513 if (!(x & 0xFFFFFFFF00000000ULL)) {
514 x <<= 32;
515 r -= 32;
516 }
517 if (!(x & 0xFFFF000000000000ULL)) {
518 x <<= 16;
519 r -= 16;
520 }
521 if (!(x & 0xFF00000000000000ULL)) {
522 x <<= 8;
523 r -= 8;
524 }
525 if (!(x & 0xF000000000000000ULL)) {
526 x <<= 4;
527 r -= 4;
528 }
529 if (!(x & 0xC000000000000000ULL)) {
530 x <<= 2;
531 r -= 2;
532 }
533 if (!(x & 0x8000000000000000ULL)) {
534 x <<= 1;
535 r -= 1;
536 }
537 return r;
538 }
539 #endif
540
541 #ifndef HAS_FLS_U32
542 static __attribute__((unused))
543 unsigned int fls_u32(uint32_t x)
544 {
545 unsigned int r = 32;
546
547 if (!x)
548 return 0;
549 if (!(x & 0xFFFF0000U)) {
550 x <<= 16;
551 r -= 16;
552 }
553 if (!(x & 0xFF000000U)) {
554 x <<= 8;
555 r -= 8;
556 }
557 if (!(x & 0xF0000000U)) {
558 x <<= 4;
559 r -= 4;
560 }
561 if (!(x & 0xC0000000U)) {
562 x <<= 2;
563 r -= 2;
564 }
565 if (!(x & 0x80000000U)) {
566 x <<= 1;
567 r -= 1;
568 }
569 return r;
570 }
571 #endif
572
573 unsigned int cds_lfht_fls_ulong(unsigned long x)
574 {
575 #if (CAA_BITS_PER_LONG == 32)
576 return fls_u32(x);
577 #else
578 return fls_u64(x);
579 #endif
580 }
581
582 /*
583 * Return the minimum order for which x <= (1UL << order).
584 * Return -1 if x is 0.
585 */
586 static
587 int cds_lfht_get_count_order_u32(uint32_t x)
588 {
589 if (!x)
590 return -1;
591
592 return fls_u32(x - 1);
593 }
594
595 /*
596 * Return the minimum order for which x <= (1UL << order).
597 * Return -1 if x is 0.
598 */
599 int cds_lfht_get_count_order_ulong(unsigned long x)
600 {
601 if (!x)
602 return -1;
603
604 return cds_lfht_fls_ulong(x - 1);
605 }
606
607 static
608 void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth);
609
610 static
611 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
612 unsigned long count);
613
614 static void mutex_lock(pthread_mutex_t *mutex)
615 {
616 int ret;
617
618 #ifndef DISTRUST_SIGNALS_EXTREME
619 ret = pthread_mutex_lock(mutex);
620 if (ret)
621 urcu_die(ret);
622 #else /* #ifndef DISTRUST_SIGNALS_EXTREME */
623 while ((ret = pthread_mutex_trylock(mutex)) != 0) {
624 if (ret != EBUSY && ret != EINTR)
625 urcu_die(ret);
626 if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) {
627 cmm_smp_mb();
628 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
629 cmm_smp_mb();
630 }
631 (void) poll(NULL, 0, 10);
632 }
633 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
634 }
635
636 static void mutex_unlock(pthread_mutex_t *mutex)
637 {
638 int ret;
639
640 ret = pthread_mutex_unlock(mutex);
641 if (ret)
642 urcu_die(ret);
643 }
644
645 static long nr_cpus_mask = -1;
646 static long split_count_mask = -1;
647 static int split_count_order = -1;
648
649 static void ht_init_nr_cpus_mask(void)
650 {
651 long maxcpus;
652
653 maxcpus = get_possible_cpus_array_len();
654 if (maxcpus <= 0) {
655 nr_cpus_mask = -2;
656 return;
657 }
658 /*
659 * round up number of CPUs to next power of two, so we
660 * can use & for modulo.
661 */
662 maxcpus = 1UL << cds_lfht_get_count_order_ulong(maxcpus);
663 nr_cpus_mask = maxcpus - 1;
664 }
665
666 static
667 void alloc_split_items_count(struct cds_lfht *ht)
668 {
669 if (nr_cpus_mask == -1) {
670 ht_init_nr_cpus_mask();
671 if (nr_cpus_mask < 0)
672 split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
673 else
674 split_count_mask = nr_cpus_mask;
675 split_count_order =
676 cds_lfht_get_count_order_ulong(split_count_mask + 1);
677 }
678
679 urcu_posix_assert(split_count_mask >= 0);
680
681 if (ht->flags & CDS_LFHT_ACCOUNTING) {
682 ht->split_count = calloc(split_count_mask + 1,
683 sizeof(struct ht_items_count));
684 urcu_posix_assert(ht->split_count);
685 } else {
686 ht->split_count = NULL;
687 }
688 }
689
690 static
691 void free_split_items_count(struct cds_lfht *ht)
692 {
693 poison_free(ht->split_count);
694 }
695
696 static
697 int ht_get_split_count_index(unsigned long hash)
698 {
699 int cpu;
700
701 urcu_posix_assert(split_count_mask >= 0);
702 cpu = urcu_sched_getcpu();
703 if (caa_unlikely(cpu < 0))
704 return hash & split_count_mask;
705 else
706 return cpu & split_count_mask;
707 }
708
709 static
710 void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash)
711 {
712 unsigned long split_count, count;
713 int index;
714
715 if (caa_unlikely(!ht->split_count))
716 return;
717 index = ht_get_split_count_index(hash);
718 split_count = uatomic_add_return(&ht->split_count[index].add, 1);
719 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
720 return;
721 /* Only if number of add multiple of 1UL << COUNT_COMMIT_ORDER */
722
723 dbg_printf("add split count %lu\n", split_count);
724 count = uatomic_add_return(&ht->count,
725 1UL << COUNT_COMMIT_ORDER);
726 if (caa_likely(count & (count - 1)))
727 return;
728 /* Only if global count is power of 2 */
729
730 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) < size)
731 return;
732 dbg_printf("add set global %lu\n", count);
733 cds_lfht_resize_lazy_count(ht, size,
734 count >> (CHAIN_LEN_TARGET - 1));
735 }
736
737 static
738 void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
739 {
740 unsigned long split_count, count;
741 int index;
742
743 if (caa_unlikely(!ht->split_count))
744 return;
745 index = ht_get_split_count_index(hash);
746 split_count = uatomic_add_return(&ht->split_count[index].del, 1);
747 if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
748 return;
749 /* Only if number of deletes multiple of 1UL << COUNT_COMMIT_ORDER */
750
751 dbg_printf("del split count %lu\n", split_count);
752 count = uatomic_add_return(&ht->count,
753 -(1UL << COUNT_COMMIT_ORDER));
754 if (caa_likely(count & (count - 1)))
755 return;
756 /* Only if global count is power of 2 */
757
758 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) >= size)
759 return;
760 dbg_printf("del set global %lu\n", count);
761 /*
762 * Don't shrink table if the number of nodes is below a
763 * certain threshold.
764 */
765 if (count < (1UL << COUNT_COMMIT_ORDER) * (split_count_mask + 1))
766 return;
767 cds_lfht_resize_lazy_count(ht, size,
768 count >> (CHAIN_LEN_TARGET - 1));
769 }
770
771 static
772 void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
773 {
774 unsigned long count;
775
776 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
777 return;
778 count = uatomic_read(&ht->count);
779 /*
780 * Use bucket-local length for small table expand and for
781 * environments lacking per-cpu data support.
782 */
783 if (count >= (1UL << (COUNT_COMMIT_ORDER + split_count_order)))
784 return;
785 if (chain_len > 100)
786 dbg_printf("WARNING: large chain length: %u.\n",
787 chain_len);
788 if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD) {
789 int growth;
790
791 /*
792 * Ideal growth calculated based on chain length.
793 */
794 growth = cds_lfht_get_count_order_u32(chain_len
795 - (CHAIN_LEN_TARGET - 1));
796 if ((ht->flags & CDS_LFHT_ACCOUNTING)
797 && (size << growth)
798 >= (1UL << (COUNT_COMMIT_ORDER
799 + split_count_order))) {
800 /*
801 * If ideal growth expands the hash table size
802 * beyond the "small hash table" sizes, use the
803 * maximum small hash table size to attempt
804 * expanding the hash table. This only applies
805 * when node accounting is available, otherwise
806 * the chain length is used to expand the hash
807 * table in every case.
808 */
809 growth = COUNT_COMMIT_ORDER + split_count_order
810 - cds_lfht_get_count_order_ulong(size);
811 if (growth <= 0)
812 return;
813 }
814 cds_lfht_resize_lazy_grow(ht, size, growth);
815 }
816 }
817
818 static
819 struct cds_lfht_node *clear_flag(struct cds_lfht_node *node)
820 {
821 return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK);
822 }
823
824 static
825 int is_removed(const struct cds_lfht_node *node)
826 {
827 return ((unsigned long) node) & REMOVED_FLAG;
828 }
829
830 static
831 int is_bucket(struct cds_lfht_node *node)
832 {
833 return ((unsigned long) node) & BUCKET_FLAG;
834 }
835
836 static
837 struct cds_lfht_node *flag_bucket(struct cds_lfht_node *node)
838 {
839 return (struct cds_lfht_node *) (((unsigned long) node) | BUCKET_FLAG);
840 }
841
842 static
843 int is_removal_owner(struct cds_lfht_node *node)
844 {
845 return ((unsigned long) node) & REMOVAL_OWNER_FLAG;
846 }
847
848 static
849 struct cds_lfht_node *flag_removed(struct cds_lfht_node *node)
850 {
851 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG);
852 }
853
854 static
855 struct cds_lfht_node *flag_removal_owner(struct cds_lfht_node *node)
856 {
857 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVAL_OWNER_FLAG);
858 }
859
860 static
861 struct cds_lfht_node *flag_removed_or_removal_owner(struct cds_lfht_node *node)
862 {
863 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG | REMOVAL_OWNER_FLAG);
864 }
865
866 static
867 struct cds_lfht_node *get_end(void)
868 {
869 return (struct cds_lfht_node *) END_VALUE;
870 }
871
872 static
873 int is_end(struct cds_lfht_node *node)
874 {
875 return clear_flag(node) == (struct cds_lfht_node *) END_VALUE;
876 }
877
878 static
879 unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr,
880 unsigned long v)
881 {
882 unsigned long old1, old2;
883
884 old1 = uatomic_read(ptr);
885 do {
886 old2 = old1;
887 if (old2 >= v)
888 return old2;
889 } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
890 return old2;
891 }
892
893 static
894 void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
895 {
896 return ht->mm->alloc_bucket_table(ht, order);
897 }
898
899 /*
900 * cds_lfht_free_bucket_table() should be called with decreasing order.
901 * When cds_lfht_free_bucket_table(0) is called, it means the whole
902 * lfht is destroyed.
903 */
904 static
905 void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order)
906 {
907 return ht->mm->free_bucket_table(ht, order);
908 }
909
910 static inline
911 struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
912 {
913 return ht->bucket_at(ht, index);
914 }
915
916 static inline
917 struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
918 unsigned long hash)
919 {
920 urcu_posix_assert(size > 0);
921 return bucket_at(ht, hash & (size - 1));
922 }
923
924 /*
925 * Remove all logically deleted nodes from a bucket up to a certain node key.
926 */
927 static
928 void _cds_lfht_gc_bucket(struct cds_lfht_node *bucket, struct cds_lfht_node *node)
929 {
930 struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
931
932 urcu_posix_assert(!is_bucket(bucket));
933 urcu_posix_assert(!is_removed(bucket));
934 urcu_posix_assert(!is_removal_owner(bucket));
935 urcu_posix_assert(!is_bucket(node));
936 urcu_posix_assert(!is_removed(node));
937 urcu_posix_assert(!is_removal_owner(node));
938 for (;;) {
939 iter_prev = bucket;
940 /* We can always skip the bucket node initially */
941 iter = rcu_dereference(iter_prev->next);
942 urcu_posix_assert(!is_removed(iter));
943 urcu_posix_assert(!is_removal_owner(iter));
944 urcu_posix_assert(iter_prev->reverse_hash <= node->reverse_hash);
945 /*
946 * We should never be called with bucket (start of chain)
947 * and logically removed node (end of path compression
948 * marker) being the actual same node. This would be a
949 * bug in the algorithm implementation.
950 */
951 urcu_posix_assert(bucket != node);
952 for (;;) {
953 if (caa_unlikely(is_end(iter)))
954 return;
955 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
956 return;
957 next = rcu_dereference(clear_flag(iter)->next);
958 if (caa_likely(is_removed(next)))
959 break;
960 iter_prev = clear_flag(iter);
961 iter = next;
962 }
963 urcu_posix_assert(!is_removed(iter));
964 urcu_posix_assert(!is_removal_owner(iter));
965 if (is_bucket(iter))
966 new_next = flag_bucket(clear_flag(next));
967 else
968 new_next = clear_flag(next);
969 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
970 }
971 }
972
973 static
974 int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
975 struct cds_lfht_node *old_node,
976 struct cds_lfht_node *old_next,
977 struct cds_lfht_node *new_node)
978 {
979 struct cds_lfht_node *bucket, *ret_next;
980
981 if (!old_node) /* Return -ENOENT if asked to replace NULL node */
982 return -ENOENT;
983
984 urcu_posix_assert(!is_removed(old_node));
985 urcu_posix_assert(!is_removal_owner(old_node));
986 urcu_posix_assert(!is_bucket(old_node));
987 urcu_posix_assert(!is_removed(new_node));
988 urcu_posix_assert(!is_removal_owner(new_node));
989 urcu_posix_assert(!is_bucket(new_node));
990 urcu_posix_assert(new_node != old_node);
991 for (;;) {
992 /* Insert after node to be replaced */
993 if (is_removed(old_next)) {
994 /*
995 * Too late, the old node has been removed under us
996 * between lookup and replace. Fail.
997 */
998 return -ENOENT;
999 }
1000 urcu_posix_assert(old_next == clear_flag(old_next));
1001 urcu_posix_assert(new_node != old_next);
1002 /*
1003 * REMOVAL_OWNER flag is _NEVER_ set before the REMOVED
1004 * flag. It is either set atomically at the same time
1005 * (replace) or after (del).
1006 */
1007 urcu_posix_assert(!is_removal_owner(old_next));
1008 new_node->next = old_next;
1009 /*
1010 * Here is the whole trick for lock-free replace: we add
1011 * the replacement node _after_ the node we want to
1012 * replace by atomically setting its next pointer at the
1013 * same time we set its removal flag. Given that
1014 * the lookups/get next use an iterator aware of the
1015 * next pointer, they will either skip the old node due
1016 * to the removal flag and see the new node, or use
1017 * the old node, but will not see the new one.
1018 * This is a replacement of a node with another node
1019 * that has the same value: we are therefore not
1020 * removing a value from the hash table. We set both the
1021 * REMOVED and REMOVAL_OWNER flags atomically so we own
1022 * the node after successful cmpxchg.
1023 */
1024 ret_next = uatomic_cmpxchg(&old_node->next,
1025 old_next, flag_removed_or_removal_owner(new_node));
1026 if (ret_next == old_next)
1027 break; /* We performed the replacement. */
1028 old_next = ret_next;
1029 }
1030
1031 /*
1032 * Ensure that the old node is not visible to readers anymore:
1033 * lookup for the node, and remove it (along with any other
1034 * logically removed node) if found.
1035 */
1036 bucket = lookup_bucket(ht, size, bit_reverse_ulong(old_node->reverse_hash));
1037 _cds_lfht_gc_bucket(bucket, new_node);
1038
1039 urcu_posix_assert(is_removed(CMM_LOAD_SHARED(old_node->next)));
1040 return 0;
1041 }
1042
1043 /*
1044 * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
1045 * mode. A NULL unique_ret allows creation of duplicate keys.
1046 */
1047 static
1048 void _cds_lfht_add(struct cds_lfht *ht,
1049 unsigned long hash,
1050 cds_lfht_match_fct match,
1051 const void *key,
1052 unsigned long size,
1053 struct cds_lfht_node *node,
1054 struct cds_lfht_iter *unique_ret,
1055 int bucket_flag)
1056 {
1057 struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
1058 *return_node;
1059 struct cds_lfht_node *bucket;
1060
1061 urcu_posix_assert(!is_bucket(node));
1062 urcu_posix_assert(!is_removed(node));
1063 urcu_posix_assert(!is_removal_owner(node));
1064 bucket = lookup_bucket(ht, size, hash);
1065 for (;;) {
1066 uint32_t chain_len = 0;
1067
1068 /*
1069 * iter_prev points to the non-removed node prior to the
1070 * insert location.
1071 */
1072 iter_prev = bucket;
1073 /* We can always skip the bucket node initially */
1074 iter = rcu_dereference(iter_prev->next);
1075 urcu_posix_assert(iter_prev->reverse_hash <= node->reverse_hash);
1076 for (;;) {
1077 if (caa_unlikely(is_end(iter)))
1078 goto insert;
1079 if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
1080 goto insert;
1081
1082 /* bucket node is the first node of the identical-hash-value chain */
1083 if (bucket_flag && clear_flag(iter)->reverse_hash == node->reverse_hash)
1084 goto insert;
1085
1086 next = rcu_dereference(clear_flag(iter)->next);
1087 if (caa_unlikely(is_removed(next)))
1088 goto gc_node;
1089
1090 /* uniquely add */
1091 if (unique_ret
1092 && !is_bucket(next)
1093 && clear_flag(iter)->reverse_hash == node->reverse_hash) {
1094 struct cds_lfht_iter d_iter = {
1095 .node = node,
1096 .next = iter,
1097 #ifdef CONFIG_CDS_LFHT_ITER_DEBUG
1098 .lfht = ht,
1099 #endif
1100 };
1101
1102 /*
1103 * uniquely adding inserts the node as the first
1104 * node of the identical-hash-value node chain.
1105 *
1106 * This semantic ensures no duplicated keys
1107 * should ever be observable in the table
1108 * (including traversing the table node by
1109 * node by forward iterations)
1110 */
1111 cds_lfht_next_duplicate(ht, match, key, &d_iter);
1112 if (!d_iter.node)
1113 goto insert;
1114
1115 *unique_ret = d_iter;
1116 return;
1117 }
1118
1119 /* Only account for identical reverse hash once */
1120 if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash
1121 && !is_bucket(next))
1122 check_resize(ht, size, ++chain_len);
1123 iter_prev = clear_flag(iter);
1124 iter = next;
1125 }
1126
1127 insert:
1128 urcu_posix_assert(node != clear_flag(iter));
1129 urcu_posix_assert(!is_removed(iter_prev));
1130 urcu_posix_assert(!is_removal_owner(iter_prev));
1131 urcu_posix_assert(!is_removed(iter));
1132 urcu_posix_assert(!is_removal_owner(iter));
1133 urcu_posix_assert(iter_prev != node);
1134 if (!bucket_flag)
1135 node->next = clear_flag(iter);
1136 else
1137 node->next = flag_bucket(clear_flag(iter));
1138 if (is_bucket(iter))
1139 new_node = flag_bucket(node);
1140 else
1141 new_node = node;
1142 if (uatomic_cmpxchg(&iter_prev->next, iter,
1143 new_node) != iter) {
1144 continue; /* retry */
1145 } else {
1146 return_node = node;
1147 goto end;
1148 }
1149
1150 gc_node:
1151 urcu_posix_assert(!is_removed(iter));
1152 urcu_posix_assert(!is_removal_owner(iter));
1153 if (is_bucket(iter))
1154 new_next = flag_bucket(clear_flag(next));
1155 else
1156 new_next = clear_flag(next);
1157 (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
1158 /* retry */
1159 }
1160 end:
1161 if (unique_ret) {
1162 unique_ret->node = return_node;
1163 /* unique_ret->next left unset, never used. */
1164 }
1165 }
1166
1167 static
1168 int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
1169 struct cds_lfht_node *node)
1170 {
1171 struct cds_lfht_node *bucket, *next;
1172
1173 if (!node) /* Return -ENOENT if asked to delete NULL node */
1174 return -ENOENT;
1175
1176 /* logically delete the node */
1177 urcu_posix_assert(!is_bucket(node));
1178 urcu_posix_assert(!is_removed(node));
1179 urcu_posix_assert(!is_removal_owner(node));
1180
1181 /*
1182 * We are first checking if the node had previously been
1183 * logically removed (this check is not atomic with setting the
1184 * logical removal flag). Return -ENOENT if the node had
1185 * previously been removed.
1186 */
1187 next = CMM_LOAD_SHARED(node->next); /* next is not dereferenced */
1188 if (caa_unlikely(is_removed(next)))
1189 return -ENOENT;
1190 urcu_posix_assert(!is_bucket(next));
1191 /*
1192 * The del operation semantic guarantees a full memory barrier
1193 * before the uatomic_or atomic commit of the deletion flag.
1194 */
1195 cmm_smp_mb__before_uatomic_or();
1196 /*
1197 * We set the REMOVED_FLAG unconditionally. Note that there may
1198 * be more than one concurrent thread setting this flag.
1199 * Knowing which wins the race will be known after the garbage
1200 * collection phase, stay tuned!
1201 */
1202 uatomic_or(&node->next, REMOVED_FLAG);
1203 /* We performed the (logical) deletion. */
1204
1205 /*
1206 * Ensure that the node is not visible to readers anymore: lookup for
1207 * the node, and remove it (along with any other logically removed node)
1208 * if found.
1209 */
1210 bucket = lookup_bucket(ht, size, bit_reverse_ulong(node->reverse_hash));
1211 _cds_lfht_gc_bucket(bucket, node);
1212
1213 urcu_posix_assert(is_removed(CMM_LOAD_SHARED(node->next)));
1214 /*
1215 * Last phase: atomically exchange node->next with a version
1216 * having "REMOVAL_OWNER_FLAG" set. If the returned node->next
1217 * pointer did _not_ have "REMOVAL_OWNER_FLAG" set, we now own
1218 * the node and win the removal race.
1219 * It is interesting to note that all "add" paths are forbidden
1220 * to change the next pointer starting from the point where the
1221 * REMOVED_FLAG is set, so here using a read, followed by a
1222 * xchg() suffice to guarantee that the xchg() will ever only
1223 * set the "REMOVAL_OWNER_FLAG" (or change nothing if the flag
1224 * was already set).
1225 */
1226 if (!is_removal_owner(uatomic_xchg(&node->next,
1227 flag_removal_owner(node->next))))
1228 return 0;
1229 else
1230 return -ENOENT;
1231 }
1232
1233 static
1234 void *partition_resize_thread(void *arg)
1235 {
1236 struct partition_resize_work *work = arg;
1237
1238 work->ht->flavor->register_thread();
1239 work->fct(work->ht, work->i, work->start, work->len);
1240 work->ht->flavor->unregister_thread();
1241 return NULL;
1242 }
1243
1244 static
1245 void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
1246 unsigned long len,
1247 void (*fct)(struct cds_lfht *ht, unsigned long i,
1248 unsigned long start, unsigned long len))
1249 {
1250 unsigned long partition_len, start = 0;
1251 struct partition_resize_work *work;
1252 int ret;
1253 unsigned long thread, nr_threads;
1254 sigset_t newmask, oldmask;
1255
1256 urcu_posix_assert(nr_cpus_mask != -1);
1257 if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD)
1258 goto fallback;
1259
1260 /*
1261 * Note: nr_cpus_mask + 1 is always power of 2.
1262 * We spawn just the number of threads we need to satisfy the minimum
1263 * partition size, up to the number of CPUs in the system.
1264 */
1265 if (nr_cpus_mask > 0) {
1266 nr_threads = min_t(unsigned long, nr_cpus_mask + 1,
1267 len >> MIN_PARTITION_PER_THREAD_ORDER);
1268 } else {
1269 nr_threads = 1;
1270 }
1271 partition_len = len >> cds_lfht_get_count_order_ulong(nr_threads);
1272 work = calloc(nr_threads, sizeof(*work));
1273 if (!work) {
1274 dbg_printf("error allocating for resize, single-threading\n");
1275 goto fallback;
1276 }
1277
1278 ret = sigfillset(&newmask);
1279 urcu_posix_assert(!ret);
1280 ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
1281 urcu_posix_assert(!ret);
1282
1283 for (thread = 0; thread < nr_threads; thread++) {
1284 work[thread].ht = ht;
1285 work[thread].i = i;
1286 work[thread].len = partition_len;
1287 work[thread].start = thread * partition_len;
1288 work[thread].fct = fct;
1289 ret = pthread_create(&(work[thread].thread_id), ht->resize_attr,
1290 partition_resize_thread, &work[thread]);
1291 if (ret == EAGAIN) {
1292 /*
1293 * Out of resources: wait and join the threads
1294 * we've created, then handle leftovers.
1295 */
1296 dbg_printf("error spawning for resize, single-threading\n");
1297 start = work[thread].start;
1298 len -= start;
1299 nr_threads = thread;
1300 break;
1301 }
1302 urcu_posix_assert(!ret);
1303 }
1304
1305 ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
1306 urcu_posix_assert(!ret);
1307
1308 for (thread = 0; thread < nr_threads; thread++) {
1309 ret = pthread_join(work[thread].thread_id, NULL);
1310 urcu_posix_assert(!ret);
1311 }
1312 free(work);
1313
1314 /*
1315 * A pthread_create failure above will either lead in us having
1316 * no threads to join or starting at a non-zero offset,
1317 * fallback to single thread processing of leftovers.
1318 */
1319 if (start == 0 && nr_threads > 0)
1320 return;
1321 fallback:
1322 fct(ht, i, start, len);
1323 }
1324
1325 /*
1326 * Holding RCU read lock to protect _cds_lfht_add against memory
1327 * reclaim that could be performed by other worker threads (ABA
1328 * problem).
1329 *
1330 * When we reach a certain length, we can split this population phase over
1331 * many worker threads, based on the number of CPUs available in the system.
1332 * This should therefore take care of not having the expand lagging behind too
1333 * many concurrent insertion threads by using the scheduler's ability to
1334 * schedule bucket node population fairly with insertions.
1335 */
1336 static
1337 void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
1338 unsigned long start, unsigned long len)
1339 {
1340 unsigned long j, size = 1UL << (i - 1);
1341
1342 urcu_posix_assert(i > MIN_TABLE_ORDER);
1343 ht->flavor->read_lock();
1344 for (j = size + start; j < size + start + len; j++) {
1345 struct cds_lfht_node *new_node = bucket_at(ht, j);
1346
1347 urcu_posix_assert(j >= size && j < (size << 1));
1348 dbg_printf("init populate: order %lu index %lu hash %lu\n",
1349 i, j, j);
1350 new_node->reverse_hash = bit_reverse_ulong(j);
1351 _cds_lfht_add(ht, j, NULL, NULL, size, new_node, NULL, 1);
1352 }
1353 ht->flavor->read_unlock();
1354 }
1355
1356 static
1357 void init_table_populate(struct cds_lfht *ht, unsigned long i,
1358 unsigned long len)
1359 {
1360 partition_resize_helper(ht, i, len, init_table_populate_partition);
1361 }
1362
1363 static
1364 void init_table(struct cds_lfht *ht,
1365 unsigned long first_order, unsigned long last_order)
1366 {
1367 unsigned long i;
1368
1369 dbg_printf("init table: first_order %lu last_order %lu\n",
1370 first_order, last_order);
1371 urcu_posix_assert(first_order > MIN_TABLE_ORDER);
1372 for (i = first_order; i <= last_order; i++) {
1373 unsigned long len;
1374
1375 len = 1UL << (i - 1);
1376 dbg_printf("init order %lu len: %lu\n", i, len);
1377
1378 /* Stop expand if the resize target changes under us */
1379 if (CMM_LOAD_SHARED(ht->resize_target) < (1UL << i))
1380 break;
1381
1382 cds_lfht_alloc_bucket_table(ht, i);
1383
1384 /*
1385 * Set all bucket nodes reverse hash values for a level and
1386 * link all bucket nodes into the table.
1387 */
1388 init_table_populate(ht, i, len);
1389
1390 /*
1391 * Update table size.
1392 */
1393 cmm_smp_wmb(); /* populate data before RCU size */
1394 CMM_STORE_SHARED(ht->size, 1UL << i);
1395
1396 dbg_printf("init new size: %lu\n", 1UL << i);
1397 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1398 break;
1399 }
1400 }
1401
1402 /*
1403 * Holding RCU read lock to protect _cds_lfht_remove against memory
1404 * reclaim that could be performed by other worker threads (ABA
1405 * problem).
1406 * For a single level, we logically remove and garbage collect each node.
1407 *
1408 * As a design choice, we perform logical removal and garbage collection on a
1409 * node-per-node basis to simplify this algorithm. We also assume keeping good
1410 * cache locality of the operation would overweight possible performance gain
1411 * that could be achieved by batching garbage collection for multiple levels.
1412 * However, this would have to be justified by benchmarks.
1413 *
1414 * Concurrent removal and add operations are helping us perform garbage
1415 * collection of logically removed nodes. We guarantee that all logically
1416 * removed nodes have been garbage-collected (unlinked) before work
1417 * enqueue is invoked to free a hole level of bucket nodes (after a
1418 * grace period).
1419 *
1420 * Logical removal and garbage collection can therefore be done in batch
1421 * or on a node-per-node basis, as long as the guarantee above holds.
1422 *
1423 * When we reach a certain length, we can split this removal over many worker
1424 * threads, based on the number of CPUs available in the system. This should
1425 * take care of not letting resize process lag behind too many concurrent
1426 * updater threads actively inserting into the hash table.
1427 */
1428 static
1429 void remove_table_partition(struct cds_lfht *ht, unsigned long i,
1430 unsigned long start, unsigned long len)
1431 {
1432 unsigned long j, size = 1UL << (i - 1);
1433
1434 urcu_posix_assert(i > MIN_TABLE_ORDER);
1435 ht->flavor->read_lock();
1436 for (j = size + start; j < size + start + len; j++) {
1437 struct cds_lfht_node *fini_bucket = bucket_at(ht, j);
1438 struct cds_lfht_node *parent_bucket = bucket_at(ht, j - size);
1439
1440 urcu_posix_assert(j >= size && j < (size << 1));
1441 dbg_printf("remove entry: order %lu index %lu hash %lu\n",
1442 i, j, j);
1443 /* Set the REMOVED_FLAG to freeze the ->next for gc */
1444 uatomic_or(&fini_bucket->next, REMOVED_FLAG);
1445 _cds_lfht_gc_bucket(parent_bucket, fini_bucket);
1446 }
1447 ht->flavor->read_unlock();
1448 }
1449
1450 static
1451 void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
1452 {
1453 partition_resize_helper(ht, i, len, remove_table_partition);
1454 }
1455
1456 /*
1457 * fini_table() is never called for first_order == 0, which is why
1458 * free_by_rcu_order == 0 can be used as criterion to know if free must
1459 * be called.
1460 */
1461 static
1462 void fini_table(struct cds_lfht *ht,
1463 unsigned long first_order, unsigned long last_order)
1464 {
1465 unsigned long free_by_rcu_order = 0, i;
1466
1467 dbg_printf("fini table: first_order %lu last_order %lu\n",
1468 first_order, last_order);
1469 urcu_posix_assert(first_order > MIN_TABLE_ORDER);
1470 for (i = last_order; i >= first_order; i--) {
1471 unsigned long len;
1472
1473 len = 1UL << (i - 1);
1474 dbg_printf("fini order %ld len: %lu\n", i, len);
1475
1476 /* Stop shrink if the resize target changes under us */
1477 if (CMM_LOAD_SHARED(ht->resize_target) > (1UL << (i - 1)))
1478 break;
1479
1480 cmm_smp_wmb(); /* populate data before RCU size */
1481 CMM_STORE_SHARED(ht->size, 1UL << (i - 1));
1482
1483 /*
1484 * We need to wait for all add operations to reach Q.S. (and
1485 * thus use the new table for lookups) before we can start
1486 * releasing the old bucket nodes. Otherwise their lookup will
1487 * return a logically removed node as insert position.
1488 */
1489 ht->flavor->update_synchronize_rcu();
1490 if (free_by_rcu_order)
1491 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
1492
1493 /*
1494 * Set "removed" flag in bucket nodes about to be removed.
1495 * Unlink all now-logically-removed bucket node pointers.
1496 * Concurrent add/remove operation are helping us doing
1497 * the gc.
1498 */
1499 remove_table(ht, i, len);
1500
1501 free_by_rcu_order = i;
1502
1503 dbg_printf("fini new size: %lu\n", 1UL << i);
1504 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1505 break;
1506 }
1507
1508 if (free_by_rcu_order) {
1509 ht->flavor->update_synchronize_rcu();
1510 cds_lfht_free_bucket_table(ht, free_by_rcu_order);
1511 }
1512 }
1513
1514 /*
1515 * Never called with size < 1.
1516 */
1517 static
1518 void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size)
1519 {
1520 struct cds_lfht_node *prev, *node;
1521 unsigned long order, len, i;
1522 int bucket_order;
1523
1524 cds_lfht_alloc_bucket_table(ht, 0);
1525
1526 dbg_printf("create bucket: order 0 index 0 hash 0\n");
1527 node = bucket_at(ht, 0);
1528 node->next = flag_bucket(get_end());
1529 node->reverse_hash = 0;
1530
1531 bucket_order = cds_lfht_get_count_order_ulong(size);
1532 urcu_posix_assert(bucket_order >= 0);
1533
1534 for (order = 1; order < (unsigned long) bucket_order + 1; order++) {
1535 len = 1UL << (order - 1);
1536 cds_lfht_alloc_bucket_table(ht, order);
1537
1538 for (i = 0; i < len; i++) {
1539 /*
1540 * Now, we are trying to init the node with the
1541 * hash=(len+i) (which is also a bucket with the
1542 * index=(len+i)) and insert it into the hash table,
1543 * so this node has to be inserted after the bucket
1544 * with the index=(len+i)&(len-1)=i. And because there
1545 * is no other non-bucket node nor bucket node with
1546 * larger index/hash inserted, so the bucket node
1547 * being inserted should be inserted directly linked
1548 * after the bucket node with index=i.
1549 */
1550 prev = bucket_at(ht, i);
1551 node = bucket_at(ht, len + i);
1552
1553 dbg_printf("create bucket: order %lu index %lu hash %lu\n",
1554 order, len + i, len + i);
1555 node->reverse_hash = bit_reverse_ulong(len + i);
1556
1557 /* insert after prev */
1558 urcu_posix_assert(is_bucket(prev->next));
1559 node->next = prev->next;
1560 prev->next = flag_bucket(node);
1561 }
1562 }
1563 }
1564
1565 #if (CAA_BITS_PER_LONG > 32)
1566 /*
1567 * For 64-bit architectures, with max number of buckets small enough not to
1568 * use the entire 64-bit memory mapping space (and allowing a fair number of
1569 * hash table instances), use the mmap allocator, which is faster. Otherwise,
1570 * fallback to the order allocator.
1571 */
1572 static
1573 const struct cds_lfht_mm_type *get_mm_type(unsigned long max_nr_buckets)
1574 {
1575 if (max_nr_buckets && max_nr_buckets <= (1ULL << 32))
1576 return &cds_lfht_mm_mmap;
1577 else
1578 return &cds_lfht_mm_order;
1579 }
1580 #else
1581 /*
1582 * For 32-bit architectures, use the order allocator.
1583 */
1584 static
1585 const struct cds_lfht_mm_type *get_mm_type(
1586 unsigned long max_nr_buckets __attribute__((unused)))
1587 {
1588 return &cds_lfht_mm_order;
1589 }
1590 #endif
1591
1592 void cds_lfht_node_init_deleted(struct cds_lfht_node *node)
1593 {
1594 cds_lfht_node_init(node);
1595 node->next = flag_removed(NULL);
1596 }
1597
1598 struct cds_lfht *_cds_lfht_new(unsigned long init_size,
1599 unsigned long min_nr_alloc_buckets,
1600 unsigned long max_nr_buckets,
1601 int flags,
1602 const struct cds_lfht_mm_type *mm,
1603 const struct rcu_flavor_struct *flavor,
1604 pthread_attr_t *attr)
1605 {
1606 struct cds_lfht *ht;
1607 unsigned long order;
1608
1609 /* min_nr_alloc_buckets must be power of two */
1610 if (!min_nr_alloc_buckets || (min_nr_alloc_buckets & (min_nr_alloc_buckets - 1)))
1611 return NULL;
1612
1613 /* init_size must be power of two */
1614 if (!init_size || (init_size & (init_size - 1)))
1615 return NULL;
1616
1617 /*
1618 * Memory management plugin default.
1619 */
1620 if (!mm)
1621 mm = get_mm_type(max_nr_buckets);
1622
1623 /* max_nr_buckets == 0 for order based mm means infinite */
1624 if (mm == &cds_lfht_mm_order && !max_nr_buckets)
1625 max_nr_buckets = 1UL << (MAX_TABLE_ORDER - 1);
1626
1627 /* max_nr_buckets must be power of two */
1628 if (!max_nr_buckets || (max_nr_buckets & (max_nr_buckets - 1)))
1629 return NULL;
1630
1631 if (flags & CDS_LFHT_AUTO_RESIZE)
1632 cds_lfht_init_worker(flavor);
1633
1634 min_nr_alloc_buckets = max(min_nr_alloc_buckets, MIN_TABLE_SIZE);
1635 init_size = max(init_size, MIN_TABLE_SIZE);
1636 max_nr_buckets = max(max_nr_buckets, min_nr_alloc_buckets);
1637 init_size = min(init_size, max_nr_buckets);
1638
1639 ht = mm->alloc_cds_lfht(min_nr_alloc_buckets, max_nr_buckets);
1640 urcu_posix_assert(ht);
1641 urcu_posix_assert(ht->mm == mm);
1642 urcu_posix_assert(ht->bucket_at == mm->bucket_at);
1643
1644 ht->flags = flags;
1645 ht->flavor = flavor;
1646 ht->resize_attr = attr;
1647 alloc_split_items_count(ht);
1648 /* this mutex should not nest in read-side C.S. */
1649 pthread_mutex_init(&ht->resize_mutex, NULL);
1650 order = cds_lfht_get_count_order_ulong(init_size);
1651 ht->resize_target = 1UL << order;
1652 cds_lfht_create_bucket(ht, 1UL << order);
1653 ht->size = 1UL << order;
1654 return ht;
1655 }
1656
1657 void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
1658 cds_lfht_match_fct match, const void *key,
1659 struct cds_lfht_iter *iter)
1660 {
1661 struct cds_lfht_node *node, *next, *bucket;
1662 unsigned long reverse_hash, size;
1663
1664 cds_lfht_iter_debug_set_ht(ht, iter);
1665
1666 reverse_hash = bit_reverse_ulong(hash);
1667
1668 size = rcu_dereference(ht->size);
1669 bucket = lookup_bucket(ht, size, hash);
1670 /* We can always skip the bucket node initially */
1671 node = rcu_dereference(bucket->next);
1672 node = clear_flag(node);
1673 for (;;) {
1674 if (caa_unlikely(is_end(node))) {
1675 node = next = NULL;
1676 break;
1677 }
1678 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1679 node = next = NULL;
1680 break;
1681 }
1682 next = rcu_dereference(node->next);
1683 urcu_posix_assert(node == clear_flag(node));
1684 if (caa_likely(!is_removed(next))
1685 && !is_bucket(next)
1686 && node->reverse_hash == reverse_hash
1687 && caa_likely(match(node, key))) {
1688 break;
1689 }
1690 node = clear_flag(next);
1691 }
1692 urcu_posix_assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1693 iter->node = node;
1694 iter->next = next;
1695 }
1696
1697 void cds_lfht_next_duplicate(struct cds_lfht *ht __attribute__((unused)),
1698 cds_lfht_match_fct match,
1699 const void *key, struct cds_lfht_iter *iter)
1700 {
1701 struct cds_lfht_node *node, *next;
1702 unsigned long reverse_hash;
1703
1704 cds_lfht_iter_debug_assert(ht == iter->lfht);
1705 node = iter->node;
1706 reverse_hash = node->reverse_hash;
1707 next = iter->next;
1708 node = clear_flag(next);
1709
1710 for (;;) {
1711 if (caa_unlikely(is_end(node))) {
1712 node = next = NULL;
1713 break;
1714 }
1715 if (caa_unlikely(node->reverse_hash > reverse_hash)) {
1716 node = next = NULL;
1717 break;
1718 }
1719 next = rcu_dereference(node->next);
1720 if (caa_likely(!is_removed(next))
1721 && !is_bucket(next)
1722 && caa_likely(match(node, key))) {
1723 break;
1724 }
1725 node = clear_flag(next);
1726 }
1727 urcu_posix_assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1728 iter->node = node;
1729 iter->next = next;
1730 }
1731
1732 void cds_lfht_next(struct cds_lfht *ht __attribute__((unused)),
1733 struct cds_lfht_iter *iter)
1734 {
1735 struct cds_lfht_node *node, *next;
1736
1737 cds_lfht_iter_debug_assert(ht == iter->lfht);
1738 node = clear_flag(iter->next);
1739 for (;;) {
1740 if (caa_unlikely(is_end(node))) {
1741 node = next = NULL;
1742 break;
1743 }
1744 next = rcu_dereference(node->next);
1745 if (caa_likely(!is_removed(next))
1746 && !is_bucket(next)) {
1747 break;
1748 }
1749 node = clear_flag(next);
1750 }
1751 urcu_posix_assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
1752 iter->node = node;
1753 iter->next = next;
1754 }
1755
1756 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1757 {
1758 cds_lfht_iter_debug_set_ht(ht, iter);
1759 /*
1760 * Get next after first bucket node. The first bucket node is the
1761 * first node of the linked list.
1762 */
1763 iter->next = bucket_at(ht, 0)->next;
1764 cds_lfht_next(ht, iter);
1765 }
1766
1767 void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
1768 struct cds_lfht_node *node)
1769 {
1770 unsigned long size;
1771
1772 node->reverse_hash = bit_reverse_ulong(hash);
1773 size = rcu_dereference(ht->size);
1774 _cds_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0);
1775 ht_count_add(ht, size, hash);
1776 }
1777
1778 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
1779 unsigned long hash,
1780 cds_lfht_match_fct match,
1781 const void *key,
1782 struct cds_lfht_node *node)
1783 {
1784 unsigned long size;
1785 struct cds_lfht_iter iter;
1786
1787 node->reverse_hash = bit_reverse_ulong(hash);
1788 size = rcu_dereference(ht->size);
1789 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1790 if (iter.node == node)
1791 ht_count_add(ht, size, hash);
1792 return iter.node;
1793 }
1794
1795 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
1796 unsigned long hash,
1797 cds_lfht_match_fct match,
1798 const void *key,
1799 struct cds_lfht_node *node)
1800 {
1801 unsigned long size;
1802 struct cds_lfht_iter iter;
1803
1804 node->reverse_hash = bit_reverse_ulong(hash);
1805 size = rcu_dereference(ht->size);
1806 for (;;) {
1807 _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
1808 if (iter.node == node) {
1809 ht_count_add(ht, size, hash);
1810 return NULL;
1811 }
1812
1813 if (!_cds_lfht_replace(ht, size, iter.node, iter.next, node))
1814 return iter.node;
1815 }
1816 }
1817
1818 int cds_lfht_replace(struct cds_lfht *ht,
1819 struct cds_lfht_iter *old_iter,
1820 unsigned long hash,
1821 cds_lfht_match_fct match,
1822 const void *key,
1823 struct cds_lfht_node *new_node)
1824 {
1825 unsigned long size;
1826
1827 new_node->reverse_hash = bit_reverse_ulong(hash);
1828 if (!old_iter->node)
1829 return -ENOENT;
1830 if (caa_unlikely(old_iter->node->reverse_hash != new_node->reverse_hash))
1831 return -EINVAL;
1832 if (caa_unlikely(!match(old_iter->node, key)))
1833 return -EINVAL;
1834 size = rcu_dereference(ht->size);
1835 return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next,
1836 new_node);
1837 }
1838
1839 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
1840 {
1841 unsigned long size;
1842 int ret;
1843
1844 size = rcu_dereference(ht->size);
1845 ret = _cds_lfht_del(ht, size, node);
1846 if (!ret) {
1847 unsigned long hash;
1848
1849 hash = bit_reverse_ulong(node->reverse_hash);
1850 ht_count_del(ht, size, hash);
1851 }
1852 return ret;
1853 }
1854
1855 int cds_lfht_is_node_deleted(const struct cds_lfht_node *node)
1856 {
1857 return is_removed(CMM_LOAD_SHARED(node->next));
1858 }
1859
1860 static
1861 int cds_lfht_delete_bucket(struct cds_lfht *ht)
1862 {
1863 struct cds_lfht_node *node;
1864 unsigned long order, i, size;
1865
1866 /* Check that the table is empty */
1867 node = bucket_at(ht, 0);
1868 do {
1869 node = clear_flag(node)->next;
1870 if (!is_bucket(node))
1871 return -EPERM;
1872 urcu_posix_assert(!is_removed(node));
1873 urcu_posix_assert(!is_removal_owner(node));
1874 } while (!is_end(node));
1875 /*
1876 * size accessed without rcu_dereference because hash table is
1877 * being destroyed.
1878 */
1879 size = ht->size;
1880 /* Internal sanity check: all nodes left should be buckets */
1881 for (i = 0; i < size; i++) {
1882 node = bucket_at(ht, i);
1883 dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
1884 i, i, bit_reverse_ulong(node->reverse_hash));
1885 urcu_posix_assert(is_bucket(node->next));
1886 }
1887
1888 for (order = cds_lfht_get_count_order_ulong(size); (long)order >= 0; order--)
1889 cds_lfht_free_bucket_table(ht, order);
1890
1891 return 0;
1892 }
1893
1894 /*
1895 * Should only be called when no more concurrent readers nor writers can
1896 * possibly access the table.
1897 */
1898 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
1899 {
1900 int ret;
1901
1902 if (ht->flags & CDS_LFHT_AUTO_RESIZE) {
1903 /* Cancel ongoing resize operations. */
1904 _CMM_STORE_SHARED(ht->in_progress_destroy, 1);
1905 /* Wait for in-flight resize operations to complete */
1906 urcu_workqueue_flush_queued_work(cds_lfht_workqueue);
1907 }
1908 ret = cds_lfht_delete_bucket(ht);
1909 if (ret)
1910 return ret;
1911 free_split_items_count(ht);
1912 if (attr)
1913 *attr = ht->resize_attr;
1914 ret = pthread_mutex_destroy(&ht->resize_mutex);
1915 if (ret)
1916 ret = -EBUSY;
1917 if (ht->flags & CDS_LFHT_AUTO_RESIZE)
1918 cds_lfht_fini_worker(ht->flavor);
1919 poison_free(ht);
1920 return ret;
1921 }
1922
1923 void cds_lfht_count_nodes(struct cds_lfht *ht,
1924 long *approx_before,
1925 unsigned long *count,
1926 long *approx_after)
1927 {
1928 struct cds_lfht_node *node, *next;
1929 unsigned long nr_bucket = 0, nr_removed = 0;
1930
1931 *approx_before = 0;
1932 if (ht->split_count) {
1933 int i;
1934
1935 for (i = 0; i < split_count_mask + 1; i++) {
1936 *approx_before += uatomic_read(&ht->split_count[i].add);
1937 *approx_before -= uatomic_read(&ht->split_count[i].del);
1938 }
1939 }
1940
1941 *count = 0;
1942
1943 /* Count non-bucket nodes in the table */
1944 node = bucket_at(ht, 0);
1945 do {
1946 next = rcu_dereference(node->next);
1947 if (is_removed(next)) {
1948 if (!is_bucket(next))
1949 (nr_removed)++;
1950 else
1951 (nr_bucket)++;
1952 } else if (!is_bucket(next))
1953 (*count)++;
1954 else
1955 (nr_bucket)++;
1956 node = clear_flag(next);
1957 } while (!is_end(node));
1958 dbg_printf("number of logically removed nodes: %lu\n", nr_removed);
1959 dbg_printf("number of bucket nodes: %lu\n", nr_bucket);
1960 *approx_after = 0;
1961 if (ht->split_count) {
1962 int i;
1963
1964 for (i = 0; i < split_count_mask + 1; i++) {
1965 *approx_after += uatomic_read(&ht->split_count[i].add);
1966 *approx_after -= uatomic_read(&ht->split_count[i].del);
1967 }
1968 }
1969 }
1970
1971 /* called with resize mutex held */
1972 static
1973 void _do_cds_lfht_grow(struct cds_lfht *ht,
1974 unsigned long old_size, unsigned long new_size)
1975 {
1976 unsigned long old_order, new_order;
1977
1978 old_order = cds_lfht_get_count_order_ulong(old_size);
1979 new_order = cds_lfht_get_count_order_ulong(new_size);
1980 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1981 old_size, old_order, new_size, new_order);
1982 urcu_posix_assert(new_size > old_size);
1983 init_table(ht, old_order + 1, new_order);
1984 }
1985
1986 /* called with resize mutex held */
1987 static
1988 void _do_cds_lfht_shrink(struct cds_lfht *ht,
1989 unsigned long old_size, unsigned long new_size)
1990 {
1991 unsigned long old_order, new_order;
1992
1993 new_size = max(new_size, MIN_TABLE_SIZE);
1994 old_order = cds_lfht_get_count_order_ulong(old_size);
1995 new_order = cds_lfht_get_count_order_ulong(new_size);
1996 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1997 old_size, old_order, new_size, new_order);
1998 urcu_posix_assert(new_size < old_size);
1999
2000 /* Remove and unlink all bucket nodes to remove. */
2001 fini_table(ht, new_order + 1, old_order);
2002 }
2003
2004
2005 /* called with resize mutex held */
2006 static
2007 void _do_cds_lfht_resize(struct cds_lfht *ht)
2008 {
2009 unsigned long new_size, old_size;
2010
2011 /*
2012 * Resize table, re-do if the target size has changed under us.
2013 */
2014 do {
2015 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
2016 break;
2017 ht->resize_initiated = 1;
2018 old_size = ht->size;
2019 new_size = CMM_LOAD_SHARED(ht->resize_target);
2020 if (old_size < new_size)
2021 _do_cds_lfht_grow(ht, old_size, new_size);
2022 else if (old_size > new_size)
2023 _do_cds_lfht_shrink(ht, old_size, new_size);
2024 ht->resize_initiated = 0;
2025 /* write resize_initiated before read resize_target */
2026 cmm_smp_mb();
2027 } while (ht->size != CMM_LOAD_SHARED(ht->resize_target));
2028 }
2029
2030 static
2031 unsigned long resize_target_grow(struct cds_lfht *ht, unsigned long new_size)
2032 {
2033 return _uatomic_xchg_monotonic_increase(&ht->resize_target, new_size);
2034 }
2035
2036 static
2037 void resize_target_update_count(struct cds_lfht *ht,
2038 unsigned long count)
2039 {
2040 count = max(count, MIN_TABLE_SIZE);
2041 count = min(count, ht->max_nr_buckets);
2042 uatomic_set(&ht->resize_target, count);
2043 }
2044
2045 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
2046 {
2047 resize_target_update_count(ht, new_size);
2048 CMM_STORE_SHARED(ht->resize_initiated, 1);
2049 mutex_lock(&ht->resize_mutex);
2050 _do_cds_lfht_resize(ht);
2051 mutex_unlock(&ht->resize_mutex);
2052 }
2053
2054 static
2055 void do_resize_cb(struct urcu_work *work)
2056 {
2057 struct resize_work *resize_work =
2058 caa_container_of(work, struct resize_work, work);
2059 struct cds_lfht *ht = resize_work->ht;
2060
2061 ht->flavor->register_thread();
2062 mutex_lock(&ht->resize_mutex);
2063 _do_cds_lfht_resize(ht);
2064 mutex_unlock(&ht->resize_mutex);
2065 ht->flavor->unregister_thread();
2066 poison_free(work);
2067 }
2068
2069 static
2070 void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht)
2071 {
2072 struct resize_work *work;
2073
2074 /* Store resize_target before read resize_initiated */
2075 cmm_smp_mb();
2076 if (!CMM_LOAD_SHARED(ht->resize_initiated)) {
2077 if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
2078 return;
2079 }
2080 work = malloc(sizeof(*work));
2081 if (work == NULL) {
2082 dbg_printf("error allocating resize work, bailing out\n");
2083 return;
2084 }
2085 work->ht = ht;
2086 urcu_workqueue_queue_work(cds_lfht_workqueue,
2087 &work->work, do_resize_cb);
2088 CMM_STORE_SHARED(ht->resize_initiated, 1);
2089 }
2090 }
2091
2092 static
2093 void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
2094 {
2095 unsigned long target_size = size << growth;
2096
2097 target_size = min(target_size, ht->max_nr_buckets);
2098 if (resize_target_grow(ht, target_size) >= target_size)
2099 return;
2100
2101 __cds_lfht_resize_lazy_launch(ht);
2102 }
2103
2104 /*
2105 * We favor grow operations over shrink. A shrink operation never occurs
2106 * if a grow operation is queued for lazy execution. A grow operation
2107 * cancels any pending shrink lazy execution.
2108 */
2109 static
2110 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
2111 unsigned long count)
2112 {
2113 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
2114 return;
2115 count = max(count, MIN_TABLE_SIZE);
2116 count = min(count, ht->max_nr_buckets);
2117 if (count == size)
2118 return; /* Already the right size, no resize needed */
2119 if (count > size) { /* lazy grow */
2120 if (resize_target_grow(ht, count) >= count)
2121 return;
2122 } else { /* lazy shrink */
2123 for (;;) {
2124 unsigned long s;
2125
2126 s = uatomic_cmpxchg(&ht->resize_target, size, count);
2127 if (s == size)
2128 break; /* no resize needed */
2129 if (s > size)
2130 return; /* growing is/(was just) in progress */
2131 if (s <= count)
2132 return; /* some other thread do shrink */
2133 size = s;
2134 }
2135 }
2136 __cds_lfht_resize_lazy_launch(ht);
2137 }
2138
2139 static void cds_lfht_before_fork(void *priv __attribute__((unused)))
2140 {
2141 if (cds_lfht_workqueue_atfork_nesting++)
2142 return;
2143 mutex_lock(&cds_lfht_fork_mutex);
2144 if (!cds_lfht_workqueue)
2145 return;
2146 urcu_workqueue_pause_worker(cds_lfht_workqueue);
2147 }
2148
2149 static void cds_lfht_after_fork_parent(void *priv __attribute__((unused)))
2150 {
2151 if (--cds_lfht_workqueue_atfork_nesting)
2152 return;
2153 if (!cds_lfht_workqueue)
2154 goto end;
2155 urcu_workqueue_resume_worker(cds_lfht_workqueue);
2156 end:
2157 mutex_unlock(&cds_lfht_fork_mutex);
2158 }
2159
2160 static void cds_lfht_after_fork_child(void *priv __attribute__((unused)))
2161 {
2162 if (--cds_lfht_workqueue_atfork_nesting)
2163 return;
2164 if (!cds_lfht_workqueue)
2165 goto end;
2166 urcu_workqueue_create_worker(cds_lfht_workqueue);
2167 end:
2168 mutex_unlock(&cds_lfht_fork_mutex);
2169 }
2170
2171 static struct urcu_atfork cds_lfht_atfork = {
2172 .before_fork = cds_lfht_before_fork,
2173 .after_fork_parent = cds_lfht_after_fork_parent,
2174 .after_fork_child = cds_lfht_after_fork_child,
2175 };
2176
2177 static void cds_lfht_init_worker(const struct rcu_flavor_struct *flavor)
2178 {
2179 flavor->register_rculfhash_atfork(&cds_lfht_atfork);
2180
2181 mutex_lock(&cds_lfht_fork_mutex);
2182 if (cds_lfht_workqueue_user_count++)
2183 goto end;
2184 cds_lfht_workqueue = urcu_workqueue_create(0, -1, NULL,
2185 NULL, NULL, NULL, NULL, NULL, NULL, NULL);
2186 end:
2187 mutex_unlock(&cds_lfht_fork_mutex);
2188 }
2189
2190 static void cds_lfht_fini_worker(const struct rcu_flavor_struct *flavor)
2191 {
2192 mutex_lock(&cds_lfht_fork_mutex);
2193 if (--cds_lfht_workqueue_user_count)
2194 goto end;
2195 urcu_workqueue_destroy(cds_lfht_workqueue);
2196 cds_lfht_workqueue = NULL;
2197 end:
2198 mutex_unlock(&cds_lfht_fork_mutex);
2199
2200 flavor->unregister_rculfhash_atfork(&cds_lfht_atfork);
2201 }
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