Fix handling of systems without sysconf nr possible cpu support
[urcu.git] / rculfhash.c
1 /*
2 * rculfhash.c
3 *
4 * Userspace RCU library - Lock-Free Resizable RCU Hash Table
5 *
6 * Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 /*
24 * Based on the following articles:
25 * - Ori Shalev and Nir Shavit. Split-ordered lists: Lock-free
26 * extensible hash tables. J. ACM 53, 3 (May 2006), 379-405.
27 * - Michael, M. M. High performance dynamic lock-free hash tables
28 * and list-based sets. In Proceedings of the fourteenth annual ACM
29 * symposium on Parallel algorithms and architectures, ACM Press,
30 * (2002), 73-82.
31 *
32 * Some specificities of this Lock-Free Resizable RCU Hash Table
33 * implementation:
34 *
35 * - RCU read-side critical section allows readers to perform hash
36 * table lookups and use the returned objects safely by delaying
37 * memory reclaim of a grace period.
38 * - Add and remove operations are lock-free, and do not need to
39 * allocate memory. They need to be executed within RCU read-side
40 * critical section to ensure the objects they read are valid and to
41 * deal with the cmpxchg ABA problem.
42 * - add and add_unique operations are supported. add_unique checks if
43 * the node key already exists in the hash table. It ensures no key
44 * duplicata exists.
45 * - The resize operation executes concurrently with add/remove/lookup.
46 * - Hash table nodes are contained within a split-ordered list. This
47 * list is ordered by incrementing reversed-bits-hash value.
48 * - An index of dummy nodes is kept. These dummy nodes are the hash
49 * table "buckets", and they are also chained together in the
50 * split-ordered list, which allows recursive expansion.
51 * - The resize operation for small tables only allows expanding the hash table.
52 * It is triggered automatically by detecting long chains in the add
53 * operation.
54 * - The resize operation for larger tables (and available through an
55 * API) allows both expanding and shrinking the hash table.
56 * - Per-CPU Split-counters are used to keep track of the number of
57 * nodes within the hash table for automatic resize triggering.
58 * - Resize operation initiated by long chain detection is executed by a
59 * call_rcu thread, which keeps lock-freedom of add and remove.
60 * - Resize operations are protected by a mutex.
61 * - The removal operation is split in two parts: first, a "removed"
62 * flag is set in the next pointer within the node to remove. Then,
63 * a "garbage collection" is performed in the bucket containing the
64 * removed node (from the start of the bucket up to the removed node).
65 * All encountered nodes with "removed" flag set in their next
66 * pointers are removed from the linked-list. If the cmpxchg used for
67 * removal fails (due to concurrent garbage-collection or concurrent
68 * add), we retry from the beginning of the bucket. This ensures that
69 * the node with "removed" flag set is removed from the hash table
70 * (not visible to lookups anymore) before the RCU read-side critical
71 * section held across removal ends. Furthermore, this ensures that
72 * the node with "removed" flag set is removed from the linked-list
73 * before its memory is reclaimed. Only the thread which removal
74 * successfully set the "removed" flag (with a cmpxchg) into a node's
75 * next pointer is considered to have succeeded its removal (and thus
76 * owns the node to reclaim). Because we garbage-collect starting from
77 * an invariant node (the start-of-bucket dummy node) up to the
78 * "removed" node (or find a reverse-hash that is higher), we are sure
79 * that a successful traversal of the chain leads to a chain that is
80 * present in the linked-list (the start node is never removed) and
81 * that is does not contain the "removed" node anymore, even if
82 * concurrent delete/add operations are changing the structure of the
83 * list concurrently.
84 * - The add operation performs gargage collection of buckets if it
85 * encounters nodes with removed flag set in the bucket where it wants
86 * to add its new node. This ensures lock-freedom of add operation by
87 * helping the remover unlink nodes from the list rather than to wait
88 * for it do to so.
89 * - A RCU "order table" indexed by log2(hash index) is copied and
90 * expanded by the resize operation. This order table allows finding
91 * the "dummy node" tables.
92 * - There is one dummy node table per hash index order. The size of
93 * each dummy node table is half the number of hashes contained in
94 * this order.
95 * - call_rcu is used to garbage-collect the old order table.
96 * - The per-order dummy node tables contain a compact version of the
97 * hash table nodes. These tables are invariant after they are
98 * populated into the hash table.
99 *
100 * A bit of ascii art explanation:
101 *
102 * Order index is the off-by-one compare to the actual power of 2 because
103 * we use index 0 to deal with the 0 special-case.
104 *
105 * This shows the nodes for a small table ordered by reversed bits:
106 *
107 * bits reverse
108 * 0 000 000
109 * 4 100 001
110 * 2 010 010
111 * 6 110 011
112 * 1 001 100
113 * 5 101 101
114 * 3 011 110
115 * 7 111 111
116 *
117 * This shows the nodes in order of non-reversed bits, linked by
118 * reversed-bit order.
119 *
120 * order bits reverse
121 * 0 0 000 000
122 * |
123 * 1 | 1 001 100 <- <-
124 * | | | |
125 * 2 | | 2 010 010 | |
126 * | | | 3 011 110 | <- |
127 * | | | | | | |
128 * 3 -> | | | 4 100 001 | |
129 * -> | | 5 101 101 |
130 * -> | 6 110 011
131 * -> 7 111 111
132 */
133
134 #define _LGPL_SOURCE
135 #include <stdlib.h>
136 #include <errno.h>
137 #include <assert.h>
138 #include <stdio.h>
139 #include <stdint.h>
140 #include <string.h>
141
142 #include "config.h"
143 #include <urcu.h>
144 #include <urcu-call-rcu.h>
145 #include <urcu/arch.h>
146 #include <urcu/uatomic.h>
147 #include <urcu/compiler.h>
148 #include <urcu/rculfhash.h>
149 #include <stdio.h>
150 #include <pthread.h>
151
152 #ifdef DEBUG
153 #define dbg_printf(fmt, args...) printf("[debug rculfhash] " fmt, ## args)
154 #else
155 #define dbg_printf(fmt, args...)
156 #endif
157
158 /*
159 * Per-CPU split-counters lazily update the global counter each 1024
160 * addition/removal. It automatically keeps track of resize required.
161 * We use the bucket length as indicator for need to expand for small
162 * tables and machines lacking per-cpu data suppport.
163 */
164 #define COUNT_COMMIT_ORDER 10
165 #define CHAIN_LEN_TARGET 1
166 #define CHAIN_LEN_RESIZE_THRESHOLD 3
167
168 /*
169 * Define the minimum table size.
170 */
171 #define MIN_TABLE_SIZE 1
172
173 #if (CAA_BITS_PER_LONG == 32)
174 #define MAX_TABLE_ORDER 32
175 #else
176 #define MAX_TABLE_ORDER 64
177 #endif
178
179 /*
180 * Minimum number of dummy nodes to touch per thread to parallelize grow/shrink.
181 */
182 #define MIN_PARTITION_PER_THREAD_ORDER 12
183 #define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
184
185 #ifndef min
186 #define min(a, b) ((a) < (b) ? (a) : (b))
187 #endif
188
189 #ifndef max
190 #define max(a, b) ((a) > (b) ? (a) : (b))
191 #endif
192
193 /*
194 * The removed flag needs to be updated atomically with the pointer.
195 * It indicates that no node must attach to the node scheduled for
196 * removal, and that node garbage collection must be performed.
197 * The dummy flag does not require to be updated atomically with the
198 * pointer, but it is added as a pointer low bit flag to save space.
199 */
200 #define REMOVED_FLAG (1UL << 0)
201 #define DUMMY_FLAG (1UL << 1)
202 #define FLAGS_MASK ((1UL << 2) - 1)
203
204 /* Value of the end pointer. Should not interact with flags. */
205 #define END_VALUE NULL
206
207 struct ht_items_count {
208 unsigned long add, del;
209 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
210
211 struct rcu_level {
212 struct rcu_head head;
213 struct _cds_lfht_node nodes[0];
214 };
215
216 struct rcu_table {
217 unsigned long size; /* always a power of 2, shared (RCU) */
218 unsigned long resize_target;
219 int resize_initiated;
220 struct rcu_level *tbl[MAX_TABLE_ORDER];
221 };
222
223 struct cds_lfht {
224 struct rcu_table t;
225 cds_lfht_hash_fct hash_fct;
226 cds_lfht_compare_fct compare_fct;
227 unsigned long hash_seed;
228 int flags;
229 /*
230 * We need to put the work threads offline (QSBR) when taking this
231 * mutex, because we use synchronize_rcu within this mutex critical
232 * section, which waits on read-side critical sections, and could
233 * therefore cause grace-period deadlock if we hold off RCU G.P.
234 * completion.
235 */
236 pthread_mutex_t resize_mutex; /* resize mutex: add/del mutex */
237 unsigned int in_progress_resize, in_progress_destroy;
238 void (*cds_lfht_call_rcu)(struct rcu_head *head,
239 void (*func)(struct rcu_head *head));
240 void (*cds_lfht_synchronize_rcu)(void);
241 void (*cds_lfht_rcu_read_lock)(void);
242 void (*cds_lfht_rcu_read_unlock)(void);
243 void (*cds_lfht_rcu_thread_offline)(void);
244 void (*cds_lfht_rcu_thread_online)(void);
245 void (*cds_lfht_rcu_register_thread)(void);
246 void (*cds_lfht_rcu_unregister_thread)(void);
247 pthread_attr_t *resize_attr; /* Resize threads attributes */
248 long count; /* global approximate item count */
249 struct ht_items_count *percpu_count; /* per-cpu item count */
250 };
251
252 struct rcu_resize_work {
253 struct rcu_head head;
254 struct cds_lfht *ht;
255 };
256
257 struct partition_resize_work {
258 struct rcu_head head;
259 struct cds_lfht *ht;
260 unsigned long i, start, len;
261 void (*fct)(struct cds_lfht *ht, unsigned long i,
262 unsigned long start, unsigned long len);
263 };
264
265 enum add_mode {
266 ADD_DEFAULT = 0,
267 ADD_UNIQUE = 1,
268 ADD_REPLACE = 2,
269 };
270
271 static
272 struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
273 unsigned long size,
274 struct cds_lfht_node *node,
275 enum add_mode mode, int dummy);
276
277 /*
278 * Algorithm to reverse bits in a word by lookup table, extended to
279 * 64-bit words.
280 * Source:
281 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
282 * Originally from Public Domain.
283 */
284
285 static const uint8_t BitReverseTable256[256] =
286 {
287 #define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
288 #define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
289 #define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
290 R6(0), R6(2), R6(1), R6(3)
291 };
292 #undef R2
293 #undef R4
294 #undef R6
295
296 static
297 uint8_t bit_reverse_u8(uint8_t v)
298 {
299 return BitReverseTable256[v];
300 }
301
302 static __attribute__((unused))
303 uint32_t bit_reverse_u32(uint32_t v)
304 {
305 return ((uint32_t) bit_reverse_u8(v) << 24) |
306 ((uint32_t) bit_reverse_u8(v >> 8) << 16) |
307 ((uint32_t) bit_reverse_u8(v >> 16) << 8) |
308 ((uint32_t) bit_reverse_u8(v >> 24));
309 }
310
311 static __attribute__((unused))
312 uint64_t bit_reverse_u64(uint64_t v)
313 {
314 return ((uint64_t) bit_reverse_u8(v) << 56) |
315 ((uint64_t) bit_reverse_u8(v >> 8) << 48) |
316 ((uint64_t) bit_reverse_u8(v >> 16) << 40) |
317 ((uint64_t) bit_reverse_u8(v >> 24) << 32) |
318 ((uint64_t) bit_reverse_u8(v >> 32) << 24) |
319 ((uint64_t) bit_reverse_u8(v >> 40) << 16) |
320 ((uint64_t) bit_reverse_u8(v >> 48) << 8) |
321 ((uint64_t) bit_reverse_u8(v >> 56));
322 }
323
324 static
325 unsigned long bit_reverse_ulong(unsigned long v)
326 {
327 #if (CAA_BITS_PER_LONG == 32)
328 return bit_reverse_u32(v);
329 #else
330 return bit_reverse_u64(v);
331 #endif
332 }
333
334 /*
335 * fls: returns the position of the most significant bit.
336 * Returns 0 if no bit is set, else returns the position of the most
337 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
338 */
339 #if defined(__i386) || defined(__x86_64)
340 static inline
341 unsigned int fls_u32(uint32_t x)
342 {
343 int r;
344
345 asm("bsrl %1,%0\n\t"
346 "jnz 1f\n\t"
347 "movl $-1,%0\n\t"
348 "1:\n\t"
349 : "=r" (r) : "rm" (x));
350 return r + 1;
351 }
352 #define HAS_FLS_U32
353 #endif
354
355 #if defined(__x86_64)
356 static inline
357 unsigned int fls_u64(uint64_t x)
358 {
359 long r;
360
361 asm("bsrq %1,%0\n\t"
362 "jnz 1f\n\t"
363 "movq $-1,%0\n\t"
364 "1:\n\t"
365 : "=r" (r) : "rm" (x));
366 return r + 1;
367 }
368 #define HAS_FLS_U64
369 #endif
370
371 #ifndef HAS_FLS_U64
372 static __attribute__((unused))
373 unsigned int fls_u64(uint64_t x)
374 {
375 unsigned int r = 64;
376
377 if (!x)
378 return 0;
379
380 if (!(x & 0xFFFFFFFF00000000ULL)) {
381 x <<= 32;
382 r -= 32;
383 }
384 if (!(x & 0xFFFF000000000000ULL)) {
385 x <<= 16;
386 r -= 16;
387 }
388 if (!(x & 0xFF00000000000000ULL)) {
389 x <<= 8;
390 r -= 8;
391 }
392 if (!(x & 0xF000000000000000ULL)) {
393 x <<= 4;
394 r -= 4;
395 }
396 if (!(x & 0xC000000000000000ULL)) {
397 x <<= 2;
398 r -= 2;
399 }
400 if (!(x & 0x8000000000000000ULL)) {
401 x <<= 1;
402 r -= 1;
403 }
404 return r;
405 }
406 #endif
407
408 #ifndef HAS_FLS_U32
409 static __attribute__((unused))
410 unsigned int fls_u32(uint32_t x)
411 {
412 unsigned int r = 32;
413
414 if (!x)
415 return 0;
416 if (!(x & 0xFFFF0000U)) {
417 x <<= 16;
418 r -= 16;
419 }
420 if (!(x & 0xFF000000U)) {
421 x <<= 8;
422 r -= 8;
423 }
424 if (!(x & 0xF0000000U)) {
425 x <<= 4;
426 r -= 4;
427 }
428 if (!(x & 0xC0000000U)) {
429 x <<= 2;
430 r -= 2;
431 }
432 if (!(x & 0x80000000U)) {
433 x <<= 1;
434 r -= 1;
435 }
436 return r;
437 }
438 #endif
439
440 unsigned int fls_ulong(unsigned long x)
441 {
442 #if (CAA_BITS_PER_lONG == 32)
443 return fls_u32(x);
444 #else
445 return fls_u64(x);
446 #endif
447 }
448
449 int get_count_order_u32(uint32_t x)
450 {
451 int order;
452
453 order = fls_u32(x) - 1;
454 if (x & (x - 1))
455 order++;
456 return order;
457 }
458
459 int get_count_order_ulong(unsigned long x)
460 {
461 int order;
462
463 order = fls_ulong(x) - 1;
464 if (x & (x - 1))
465 order++;
466 return order;
467 }
468
469 #ifdef POISON_FREE
470 #define poison_free(ptr) \
471 do { \
472 memset(ptr, 0x42, sizeof(*(ptr))); \
473 free(ptr); \
474 } while (0)
475 #else
476 #define poison_free(ptr) free(ptr)
477 #endif
478
479 static
480 void cds_lfht_resize_lazy(struct cds_lfht *ht, unsigned long size, int growth);
481
482 /*
483 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
484 * available, then we support hash table item accounting.
485 * In the unfortunate event the number of CPUs reported would be
486 * inaccurate, we use modulo arithmetic on the number of CPUs we got.
487 */
488 #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
489
490 static
491 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
492 unsigned long count);
493
494 static long nr_cpus_mask = -1;
495
496 static
497 struct ht_items_count *alloc_per_cpu_items_count(void)
498 {
499 struct ht_items_count *count;
500
501 switch (nr_cpus_mask) {
502 case -2:
503 return NULL;
504 case -1:
505 {
506 long maxcpus;
507
508 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
509 if (maxcpus <= 0) {
510 nr_cpus_mask = -2;
511 return NULL;
512 }
513 /*
514 * round up number of CPUs to next power of two, so we
515 * can use & for modulo.
516 */
517 maxcpus = 1UL << get_count_order_ulong(maxcpus);
518 nr_cpus_mask = maxcpus - 1;
519 }
520 /* Fall-through */
521 default:
522 return calloc(nr_cpus_mask + 1, sizeof(*count));
523 }
524 }
525
526 static
527 void free_per_cpu_items_count(struct ht_items_count *count)
528 {
529 poison_free(count);
530 }
531
532 static
533 int ht_get_cpu(void)
534 {
535 int cpu;
536
537 assert(nr_cpus_mask >= 0);
538 cpu = sched_getcpu();
539 if (unlikely(cpu < 0))
540 return cpu;
541 else
542 return cpu & nr_cpus_mask;
543 }
544
545 static
546 void ht_count_add(struct cds_lfht *ht, unsigned long size)
547 {
548 unsigned long percpu_count;
549 int cpu;
550
551 if (unlikely(!ht->percpu_count))
552 return;
553 cpu = ht_get_cpu();
554 if (unlikely(cpu < 0))
555 return;
556 percpu_count = uatomic_add_return(&ht->percpu_count[cpu].add, 1);
557 if (unlikely(!(percpu_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) {
558 long count;
559
560 dbg_printf("add percpu %lu\n", percpu_count);
561 count = uatomic_add_return(&ht->count,
562 1UL << COUNT_COMMIT_ORDER);
563 /* If power of 2 */
564 if (!(count & (count - 1))) {
565 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) < size)
566 return;
567 dbg_printf("add set global %ld\n", count);
568 cds_lfht_resize_lazy_count(ht, size,
569 count >> (CHAIN_LEN_TARGET - 1));
570 }
571 }
572 }
573
574 static
575 void ht_count_del(struct cds_lfht *ht, unsigned long size)
576 {
577 unsigned long percpu_count;
578 int cpu;
579
580 if (unlikely(!ht->percpu_count))
581 return;
582 cpu = ht_get_cpu();
583 if (unlikely(cpu < 0))
584 return;
585 percpu_count = uatomic_add_return(&ht->percpu_count[cpu].del, 1);
586 if (unlikely(!(percpu_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) {
587 long count;
588
589 dbg_printf("del percpu %lu\n", percpu_count);
590 count = uatomic_add_return(&ht->count,
591 -(1UL << COUNT_COMMIT_ORDER));
592 /* If power of 2 */
593 if (!(count & (count - 1))) {
594 if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) >= size)
595 return;
596 dbg_printf("del set global %ld\n", count);
597 /*
598 * Don't shrink table if the number of nodes is below a
599 * certain threshold.
600 */
601 if (count < (1UL << COUNT_COMMIT_ORDER) * (nr_cpus_mask + 1))
602 return;
603 cds_lfht_resize_lazy_count(ht, size,
604 count >> (CHAIN_LEN_TARGET - 1));
605 }
606 }
607 }
608
609 #else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
610
611 static const long nr_cpus_mask = -2;
612
613 static
614 struct ht_items_count *alloc_per_cpu_items_count(void)
615 {
616 return NULL;
617 }
618
619 static
620 void free_per_cpu_items_count(struct ht_items_count *count)
621 {
622 }
623
624 static
625 void ht_count_add(struct cds_lfht *ht, unsigned long size)
626 {
627 }
628
629 static
630 void ht_count_del(struct cds_lfht *ht, unsigned long size)
631 {
632 }
633
634 #endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
635
636
637 static
638 void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
639 {
640 unsigned long count;
641
642 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
643 return;
644 count = uatomic_read(&ht->count);
645 /*
646 * Use bucket-local length for small table expand and for
647 * environments lacking per-cpu data support.
648 */
649 if (count >= (1UL << COUNT_COMMIT_ORDER))
650 return;
651 if (chain_len > 100)
652 dbg_printf("WARNING: large chain length: %u.\n",
653 chain_len);
654 if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
655 cds_lfht_resize_lazy(ht, size,
656 get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1)));
657 }
658
659 static
660 struct cds_lfht_node *clear_flag(struct cds_lfht_node *node)
661 {
662 return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK);
663 }
664
665 static
666 int is_removed(struct cds_lfht_node *node)
667 {
668 return ((unsigned long) node) & REMOVED_FLAG;
669 }
670
671 static
672 struct cds_lfht_node *flag_removed(struct cds_lfht_node *node)
673 {
674 return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG);
675 }
676
677 static
678 int is_dummy(struct cds_lfht_node *node)
679 {
680 return ((unsigned long) node) & DUMMY_FLAG;
681 }
682
683 static
684 struct cds_lfht_node *flag_dummy(struct cds_lfht_node *node)
685 {
686 return (struct cds_lfht_node *) (((unsigned long) node) | DUMMY_FLAG);
687 }
688
689 static
690 struct cds_lfht_node *get_end(void)
691 {
692 return (struct cds_lfht_node *) END_VALUE;
693 }
694
695 static
696 int is_end(struct cds_lfht_node *node)
697 {
698 return clear_flag(node) == (struct cds_lfht_node *) END_VALUE;
699 }
700
701 static
702 unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
703 {
704 unsigned long old1, old2;
705
706 old1 = uatomic_read(ptr);
707 do {
708 old2 = old1;
709 if (old2 >= v)
710 return old2;
711 } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
712 return v;
713 }
714
715 static
716 void cds_lfht_free_level(struct rcu_head *head)
717 {
718 struct rcu_level *l =
719 caa_container_of(head, struct rcu_level, head);
720 poison_free(l);
721 }
722
723 /*
724 * Remove all logically deleted nodes from a bucket up to a certain node key.
725 */
726 static
727 void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node)
728 {
729 struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
730
731 assert(!is_dummy(dummy));
732 assert(!is_removed(dummy));
733 assert(!is_dummy(node));
734 assert(!is_removed(node));
735 for (;;) {
736 iter_prev = dummy;
737 /* We can always skip the dummy node initially */
738 iter = rcu_dereference(iter_prev->p.next);
739 assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
740 /*
741 * We should never be called with dummy (start of chain)
742 * and logically removed node (end of path compression
743 * marker) being the actual same node. This would be a
744 * bug in the algorithm implementation.
745 */
746 assert(dummy != node);
747 for (;;) {
748 if (unlikely(is_end(iter)))
749 return;
750 if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
751 return;
752 next = rcu_dereference(clear_flag(iter)->p.next);
753 if (likely(is_removed(next)))
754 break;
755 iter_prev = clear_flag(iter);
756 iter = next;
757 }
758 assert(!is_removed(iter));
759 if (is_dummy(iter))
760 new_next = flag_dummy(clear_flag(next));
761 else
762 new_next = clear_flag(next);
763 if (is_removed(iter))
764 new_next = flag_removed(new_next);
765 (void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next);
766 }
767 return;
768 }
769
770 static
771 int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
772 struct cds_lfht_node *old_node,
773 struct cds_lfht_node *ret_next,
774 struct cds_lfht_node *new_node)
775 {
776 struct cds_lfht_node *dummy, *old_next;
777 struct _cds_lfht_node *lookup;
778 int flagged = 0;
779 unsigned long hash, index, order;
780
781 if (!old_node) /* Return -ENOENT if asked to replace NULL node */
782 goto end;
783
784 assert(!is_removed(old_node));
785 assert(!is_dummy(old_node));
786 assert(!is_removed(new_node));
787 assert(!is_dummy(new_node));
788 assert(new_node != old_node);
789 do {
790 /* Insert after node to be replaced */
791 old_next = ret_next;
792 if (is_removed(old_next)) {
793 /*
794 * Too late, the old node has been removed under us
795 * between lookup and replace. Fail.
796 */
797 goto end;
798 }
799 assert(!is_dummy(old_next));
800 assert(new_node != clear_flag(old_next));
801 new_node->p.next = clear_flag(old_next);
802 /*
803 * Here is the whole trick for lock-free replace: we add
804 * the replacement node _after_ the node we want to
805 * replace by atomically setting its next pointer at the
806 * same time we set its removal flag. Given that
807 * the lookups/get next use an iterator aware of the
808 * next pointer, they will either skip the old node due
809 * to the removal flag and see the new node, or use
810 * the old node, but will not see the new one.
811 */
812 ret_next = uatomic_cmpxchg(&old_node->p.next,
813 old_next, flag_removed(new_node));
814 } while (ret_next != old_next);
815
816 /* We performed the replacement. */
817 flagged = 1;
818
819 /*
820 * Ensure that the old node is not visible to readers anymore:
821 * lookup for the node, and remove it (along with any other
822 * logically removed node) if found.
823 */
824 hash = bit_reverse_ulong(old_node->p.reverse_hash);
825 assert(size > 0);
826 index = hash & (size - 1);
827 order = get_count_order_ulong(index + 1);
828 lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
829 dummy = (struct cds_lfht_node *) lookup;
830 _cds_lfht_gc_bucket(dummy, new_node);
831 end:
832 /*
833 * Only the flagging action indicated that we (and no other)
834 * replaced the node from the hash table.
835 */
836 if (flagged) {
837 assert(is_removed(rcu_dereference(old_node->p.next)));
838 return 0;
839 } else {
840 return -ENOENT;
841 }
842 }
843
844 static
845 struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
846 unsigned long size,
847 struct cds_lfht_node *node,
848 enum add_mode mode, int dummy)
849 {
850 struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
851 *dummy_node, *return_node;
852 struct _cds_lfht_node *lookup;
853 unsigned long hash, index, order;
854
855 assert(!is_dummy(node));
856 assert(!is_removed(node));
857 if (!size) {
858 assert(dummy);
859 node->p.next = flag_dummy(get_end());
860 return node; /* Initial first add (head) */
861 }
862 hash = bit_reverse_ulong(node->p.reverse_hash);
863 for (;;) {
864 uint32_t chain_len = 0;
865
866 /*
867 * iter_prev points to the non-removed node prior to the
868 * insert location.
869 */
870 index = hash & (size - 1);
871 order = get_count_order_ulong(index + 1);
872 lookup = &ht->t.tbl[order]->nodes[index & ((!order ? 0 : (1UL << (order - 1))) - 1)];
873 iter_prev = (struct cds_lfht_node *) lookup;
874 /* We can always skip the dummy node initially */
875 iter = rcu_dereference(iter_prev->p.next);
876 assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
877 for (;;) {
878 if (unlikely(is_end(iter)))
879 goto insert;
880 if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
881 goto insert;
882 next = rcu_dereference(clear_flag(iter)->p.next);
883 if (unlikely(is_removed(next)))
884 goto gc_node;
885 if ((mode == ADD_UNIQUE || mode == ADD_REPLACE)
886 && !is_dummy(next)
887 && !ht->compare_fct(node->key, node->key_len,
888 clear_flag(iter)->key,
889 clear_flag(iter)->key_len)) {
890 if (mode == ADD_UNIQUE)
891 return clear_flag(iter);
892 else /* mode == ADD_REPLACE */
893 goto replace;
894 }
895 /* Only account for identical reverse hash once */
896 if (iter_prev->p.reverse_hash != clear_flag(iter)->p.reverse_hash
897 && !is_dummy(next))
898 check_resize(ht, size, ++chain_len);
899 iter_prev = clear_flag(iter);
900 iter = next;
901 }
902
903 insert:
904 assert(node != clear_flag(iter));
905 assert(!is_removed(iter_prev));
906 assert(!is_removed(iter));
907 assert(iter_prev != node);
908 if (!dummy)
909 node->p.next = clear_flag(iter);
910 else
911 node->p.next = flag_dummy(clear_flag(iter));
912 if (is_dummy(iter))
913 new_node = flag_dummy(node);
914 else
915 new_node = node;
916 if (uatomic_cmpxchg(&iter_prev->p.next, iter,
917 new_node) != iter) {
918 continue; /* retry */
919 } else {
920 if (mode == ADD_REPLACE)
921 return_node = NULL;
922 else /* ADD_DEFAULT and ADD_UNIQUE */
923 return_node = node;
924 goto gc_end;
925 }
926
927 replace:
928
929 if (!_cds_lfht_replace(ht, size, clear_flag(iter), next,
930 node)) {
931 return_node = clear_flag(iter);
932 goto end; /* gc already done */
933 } else {
934 continue; /* retry */
935 }
936
937 gc_node:
938 assert(!is_removed(iter));
939 if (is_dummy(iter))
940 new_next = flag_dummy(clear_flag(next));
941 else
942 new_next = clear_flag(next);
943 (void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next);
944 /* retry */
945 }
946 gc_end:
947 /* Garbage collect logically removed nodes in the bucket */
948 index = hash & (size - 1);
949 order = get_count_order_ulong(index + 1);
950 lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
951 dummy_node = (struct cds_lfht_node *) lookup;
952 _cds_lfht_gc_bucket(dummy_node, node);
953 end:
954 return return_node;
955 }
956
957 static
958 int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
959 struct cds_lfht_node *node,
960 int dummy_removal)
961 {
962 struct cds_lfht_node *dummy, *next, *old;
963 struct _cds_lfht_node *lookup;
964 int flagged = 0;
965 unsigned long hash, index, order;
966
967 if (!node) /* Return -ENOENT if asked to delete NULL node */
968 goto end;
969
970 /* logically delete the node */
971 assert(!is_dummy(node));
972 assert(!is_removed(node));
973 old = rcu_dereference(node->p.next);
974 do {
975 struct cds_lfht_node *new_next;
976
977 next = old;
978 if (unlikely(is_removed(next)))
979 goto end;
980 if (dummy_removal)
981 assert(is_dummy(next));
982 else
983 assert(!is_dummy(next));
984 new_next = flag_removed(next);
985 old = uatomic_cmpxchg(&node->p.next, next, new_next);
986 } while (old != next);
987
988 /* We performed the (logical) deletion. */
989 flagged = 1;
990
991 /*
992 * Ensure that the node is not visible to readers anymore: lookup for
993 * the node, and remove it (along with any other logically removed node)
994 * if found.
995 */
996 hash = bit_reverse_ulong(node->p.reverse_hash);
997 assert(size > 0);
998 index = hash & (size - 1);
999 order = get_count_order_ulong(index + 1);
1000 lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
1001 dummy = (struct cds_lfht_node *) lookup;
1002 _cds_lfht_gc_bucket(dummy, node);
1003 end:
1004 /*
1005 * Only the flagging action indicated that we (and no other)
1006 * removed the node from the hash.
1007 */
1008 if (flagged) {
1009 assert(is_removed(rcu_dereference(node->p.next)));
1010 return 0;
1011 } else {
1012 return -ENOENT;
1013 }
1014 }
1015
1016 static
1017 void *partition_resize_thread(void *arg)
1018 {
1019 struct partition_resize_work *work = arg;
1020
1021 work->ht->cds_lfht_rcu_register_thread();
1022 work->fct(work->ht, work->i, work->start, work->len);
1023 work->ht->cds_lfht_rcu_unregister_thread();
1024 return NULL;
1025 }
1026
1027 static
1028 void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
1029 unsigned long len,
1030 void (*fct)(struct cds_lfht *ht, unsigned long i,
1031 unsigned long start, unsigned long len))
1032 {
1033 unsigned long partition_len;
1034 struct partition_resize_work *work;
1035 int thread, ret;
1036 unsigned long nr_threads;
1037 pthread_t *thread_id;
1038
1039 /*
1040 * Note: nr_cpus_mask + 1 is always power of 2.
1041 * We spawn just the number of threads we need to satisfy the minimum
1042 * partition size, up to the number of CPUs in the system.
1043 */
1044 if (nr_cpus_mask > 0) {
1045 nr_threads = min(nr_cpus_mask + 1,
1046 len >> MIN_PARTITION_PER_THREAD_ORDER);
1047 } else {
1048 nr_threads = 1;
1049 }
1050 partition_len = len >> get_count_order_ulong(nr_threads);
1051 work = calloc(nr_threads, sizeof(*work));
1052 thread_id = calloc(nr_threads, sizeof(*thread_id));
1053 assert(work);
1054 for (thread = 0; thread < nr_threads; thread++) {
1055 work[thread].ht = ht;
1056 work[thread].i = i;
1057 work[thread].len = partition_len;
1058 work[thread].start = thread * partition_len;
1059 work[thread].fct = fct;
1060 ret = pthread_create(&thread_id[thread], ht->resize_attr,
1061 partition_resize_thread, &work[thread]);
1062 assert(!ret);
1063 }
1064 for (thread = 0; thread < nr_threads; thread++) {
1065 ret = pthread_join(thread_id[thread], NULL);
1066 assert(!ret);
1067 }
1068 free(work);
1069 free(thread_id);
1070 }
1071
1072 /*
1073 * Holding RCU read lock to protect _cds_lfht_add against memory
1074 * reclaim that could be performed by other call_rcu worker threads (ABA
1075 * problem).
1076 *
1077 * When we reach a certain length, we can split this population phase over
1078 * many worker threads, based on the number of CPUs available in the system.
1079 * This should therefore take care of not having the expand lagging behind too
1080 * many concurrent insertion threads by using the scheduler's ability to
1081 * schedule dummy node population fairly with insertions.
1082 */
1083 static
1084 void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
1085 unsigned long start, unsigned long len)
1086 {
1087 unsigned long j;
1088
1089 ht->cds_lfht_rcu_read_lock();
1090 for (j = start; j < start + len; j++) {
1091 struct cds_lfht_node *new_node =
1092 (struct cds_lfht_node *) &ht->t.tbl[i]->nodes[j];
1093
1094 dbg_printf("init populate: i %lu j %lu hash %lu\n",
1095 i, j, !i ? 0 : (1UL << (i - 1)) + j);
1096 new_node->p.reverse_hash =
1097 bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
1098 (void) _cds_lfht_add(ht, !i ? 0 : (1UL << (i - 1)),
1099 new_node, ADD_DEFAULT, 1);
1100 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1101 break;
1102 }
1103 ht->cds_lfht_rcu_read_unlock();
1104 }
1105
1106 static
1107 void init_table_populate(struct cds_lfht *ht, unsigned long i,
1108 unsigned long len)
1109 {
1110 assert(nr_cpus_mask != -1);
1111 if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) {
1112 ht->cds_lfht_rcu_thread_online();
1113 init_table_populate_partition(ht, i, 0, len);
1114 ht->cds_lfht_rcu_thread_offline();
1115 return;
1116 }
1117 partition_resize_helper(ht, i, len, init_table_populate_partition);
1118 }
1119
1120 static
1121 void init_table(struct cds_lfht *ht,
1122 unsigned long first_order, unsigned long len_order)
1123 {
1124 unsigned long i, end_order;
1125
1126 dbg_printf("init table: first_order %lu end_order %lu\n",
1127 first_order, first_order + len_order);
1128 end_order = first_order + len_order;
1129 for (i = first_order; i < end_order; i++) {
1130 unsigned long len;
1131
1132 len = !i ? 1 : 1UL << (i - 1);
1133 dbg_printf("init order %lu len: %lu\n", i, len);
1134
1135 /* Stop expand if the resize target changes under us */
1136 if (CMM_LOAD_SHARED(ht->t.resize_target) < (!i ? 1 : (1UL << i)))
1137 break;
1138
1139 ht->t.tbl[i] = calloc(1, sizeof(struct rcu_level)
1140 + (len * sizeof(struct _cds_lfht_node)));
1141 assert(ht->t.tbl[i]);
1142
1143 /*
1144 * Set all dummy nodes reverse hash values for a level and
1145 * link all dummy nodes into the table.
1146 */
1147 init_table_populate(ht, i, len);
1148
1149 /*
1150 * Update table size.
1151 */
1152 cmm_smp_wmb(); /* populate data before RCU size */
1153 CMM_STORE_SHARED(ht->t.size, !i ? 1 : (1UL << i));
1154
1155 dbg_printf("init new size: %lu\n", !i ? 1 : (1UL << i));
1156 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1157 break;
1158 }
1159 }
1160
1161 /*
1162 * Holding RCU read lock to protect _cds_lfht_remove against memory
1163 * reclaim that could be performed by other call_rcu worker threads (ABA
1164 * problem).
1165 * For a single level, we logically remove and garbage collect each node.
1166 *
1167 * As a design choice, we perform logical removal and garbage collection on a
1168 * node-per-node basis to simplify this algorithm. We also assume keeping good
1169 * cache locality of the operation would overweight possible performance gain
1170 * that could be achieved by batching garbage collection for multiple levels.
1171 * However, this would have to be justified by benchmarks.
1172 *
1173 * Concurrent removal and add operations are helping us perform garbage
1174 * collection of logically removed nodes. We guarantee that all logically
1175 * removed nodes have been garbage-collected (unlinked) before call_rcu is
1176 * invoked to free a hole level of dummy nodes (after a grace period).
1177 *
1178 * Logical removal and garbage collection can therefore be done in batch or on a
1179 * node-per-node basis, as long as the guarantee above holds.
1180 *
1181 * When we reach a certain length, we can split this removal over many worker
1182 * threads, based on the number of CPUs available in the system. This should
1183 * take care of not letting resize process lag behind too many concurrent
1184 * updater threads actively inserting into the hash table.
1185 */
1186 static
1187 void remove_table_partition(struct cds_lfht *ht, unsigned long i,
1188 unsigned long start, unsigned long len)
1189 {
1190 unsigned long j;
1191
1192 ht->cds_lfht_rcu_read_lock();
1193 for (j = start; j < start + len; j++) {
1194 struct cds_lfht_node *fini_node =
1195 (struct cds_lfht_node *) &ht->t.tbl[i]->nodes[j];
1196
1197 dbg_printf("remove entry: i %lu j %lu hash %lu\n",
1198 i, j, !i ? 0 : (1UL << (i - 1)) + j);
1199 fini_node->p.reverse_hash =
1200 bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
1201 (void) _cds_lfht_del(ht, !i ? 0 : (1UL << (i - 1)),
1202 fini_node, 1);
1203 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1204 break;
1205 }
1206 ht->cds_lfht_rcu_read_unlock();
1207 }
1208
1209 static
1210 void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
1211 {
1212
1213 assert(nr_cpus_mask != -1);
1214 if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) {
1215 ht->cds_lfht_rcu_thread_online();
1216 remove_table_partition(ht, i, 0, len);
1217 ht->cds_lfht_rcu_thread_offline();
1218 return;
1219 }
1220 partition_resize_helper(ht, i, len, remove_table_partition);
1221 }
1222
1223 static
1224 void fini_table(struct cds_lfht *ht,
1225 unsigned long first_order, unsigned long len_order)
1226 {
1227 long i, end_order;
1228
1229 dbg_printf("fini table: first_order %lu end_order %lu\n",
1230 first_order, first_order + len_order);
1231 end_order = first_order + len_order;
1232 assert(first_order > 0);
1233 for (i = end_order - 1; i >= first_order; i--) {
1234 unsigned long len;
1235
1236 len = !i ? 1 : 1UL << (i - 1);
1237 dbg_printf("fini order %lu len: %lu\n", i, len);
1238
1239 /* Stop shrink if the resize target changes under us */
1240 if (CMM_LOAD_SHARED(ht->t.resize_target) > (1UL << (i - 1)))
1241 break;
1242
1243 cmm_smp_wmb(); /* populate data before RCU size */
1244 CMM_STORE_SHARED(ht->t.size, 1UL << (i - 1));
1245
1246 /*
1247 * We need to wait for all add operations to reach Q.S. (and
1248 * thus use the new table for lookups) before we can start
1249 * releasing the old dummy nodes. Otherwise their lookup will
1250 * return a logically removed node as insert position.
1251 */
1252 ht->cds_lfht_synchronize_rcu();
1253
1254 /*
1255 * Set "removed" flag in dummy nodes about to be removed.
1256 * Unlink all now-logically-removed dummy node pointers.
1257 * Concurrent add/remove operation are helping us doing
1258 * the gc.
1259 */
1260 remove_table(ht, i, len);
1261
1262 ht->cds_lfht_call_rcu(&ht->t.tbl[i]->head, cds_lfht_free_level);
1263
1264 dbg_printf("fini new size: %lu\n", 1UL << i);
1265 if (CMM_LOAD_SHARED(ht->in_progress_destroy))
1266 break;
1267 }
1268 }
1269
1270 struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
1271 cds_lfht_compare_fct compare_fct,
1272 unsigned long hash_seed,
1273 unsigned long init_size,
1274 int flags,
1275 void (*cds_lfht_call_rcu)(struct rcu_head *head,
1276 void (*func)(struct rcu_head *head)),
1277 void (*cds_lfht_synchronize_rcu)(void),
1278 void (*cds_lfht_rcu_read_lock)(void),
1279 void (*cds_lfht_rcu_read_unlock)(void),
1280 void (*cds_lfht_rcu_thread_offline)(void),
1281 void (*cds_lfht_rcu_thread_online)(void),
1282 void (*cds_lfht_rcu_register_thread)(void),
1283 void (*cds_lfht_rcu_unregister_thread)(void),
1284 pthread_attr_t *attr)
1285 {
1286 struct cds_lfht *ht;
1287 unsigned long order;
1288
1289 /* init_size must be power of two */
1290 if (init_size && (init_size & (init_size - 1)))
1291 return NULL;
1292 ht = calloc(1, sizeof(struct cds_lfht));
1293 assert(ht);
1294 ht->hash_fct = hash_fct;
1295 ht->compare_fct = compare_fct;
1296 ht->hash_seed = hash_seed;
1297 ht->cds_lfht_call_rcu = cds_lfht_call_rcu;
1298 ht->cds_lfht_synchronize_rcu = cds_lfht_synchronize_rcu;
1299 ht->cds_lfht_rcu_read_lock = cds_lfht_rcu_read_lock;
1300 ht->cds_lfht_rcu_read_unlock = cds_lfht_rcu_read_unlock;
1301 ht->cds_lfht_rcu_thread_offline = cds_lfht_rcu_thread_offline;
1302 ht->cds_lfht_rcu_thread_online = cds_lfht_rcu_thread_online;
1303 ht->cds_lfht_rcu_register_thread = cds_lfht_rcu_register_thread;
1304 ht->cds_lfht_rcu_unregister_thread = cds_lfht_rcu_unregister_thread;
1305 ht->resize_attr = attr;
1306 ht->percpu_count = alloc_per_cpu_items_count();
1307 /* this mutex should not nest in read-side C.S. */
1308 pthread_mutex_init(&ht->resize_mutex, NULL);
1309 order = get_count_order_ulong(max(init_size, MIN_TABLE_SIZE)) + 1;
1310 ht->flags = flags;
1311 ht->cds_lfht_rcu_thread_offline();
1312 pthread_mutex_lock(&ht->resize_mutex);
1313 ht->t.resize_target = 1UL << (order - 1);
1314 init_table(ht, 0, order);
1315 pthread_mutex_unlock(&ht->resize_mutex);
1316 ht->cds_lfht_rcu_thread_online();
1317 return ht;
1318 }
1319
1320 void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
1321 struct cds_lfht_iter *iter)
1322 {
1323 struct cds_lfht_node *node, *next, *dummy_node;
1324 struct _cds_lfht_node *lookup;
1325 unsigned long hash, reverse_hash, index, order, size;
1326
1327 hash = ht->hash_fct(key, key_len, ht->hash_seed);
1328 reverse_hash = bit_reverse_ulong(hash);
1329
1330 size = rcu_dereference(ht->t.size);
1331 index = hash & (size - 1);
1332 order = get_count_order_ulong(index + 1);
1333 lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1))) - 1)];
1334 dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
1335 hash, index, order, index & (!order ? 0 : ((1UL << (order - 1)) - 1)));
1336 dummy_node = (struct cds_lfht_node *) lookup;
1337 /* We can always skip the dummy node initially */
1338 node = rcu_dereference(dummy_node->p.next);
1339 node = clear_flag(node);
1340 for (;;) {
1341 if (unlikely(is_end(node))) {
1342 node = next = NULL;
1343 break;
1344 }
1345 if (unlikely(node->p.reverse_hash > reverse_hash)) {
1346 node = next = NULL;
1347 break;
1348 }
1349 next = rcu_dereference(node->p.next);
1350 if (likely(!is_removed(next))
1351 && !is_dummy(next)
1352 && likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
1353 break;
1354 }
1355 node = clear_flag(next);
1356 }
1357 assert(!node || !is_dummy(rcu_dereference(node->p.next)));
1358 iter->node = node;
1359 iter->next = next;
1360 }
1361
1362 void cds_lfht_next_duplicate(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1363 {
1364 struct cds_lfht_node *node, *next;
1365 unsigned long reverse_hash;
1366 void *key;
1367 size_t key_len;
1368
1369 node = iter->node;
1370 reverse_hash = node->p.reverse_hash;
1371 key = node->key;
1372 key_len = node->key_len;
1373 next = iter->next;
1374 node = clear_flag(next);
1375
1376 for (;;) {
1377 if (unlikely(is_end(node))) {
1378 node = next = NULL;
1379 break;
1380 }
1381 if (unlikely(node->p.reverse_hash > reverse_hash)) {
1382 node = next = NULL;
1383 break;
1384 }
1385 next = rcu_dereference(node->p.next);
1386 if (likely(!is_removed(next))
1387 && !is_dummy(next)
1388 && likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
1389 break;
1390 }
1391 node = clear_flag(next);
1392 }
1393 assert(!node || !is_dummy(rcu_dereference(node->p.next)));
1394 iter->node = node;
1395 iter->next = next;
1396 }
1397
1398 void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1399 {
1400 struct cds_lfht_node *node, *next;
1401
1402 node = iter->node;
1403 next = iter->next;
1404 node = clear_flag(next);
1405
1406 for (;;) {
1407 if (unlikely(is_end(node))) {
1408 node = next = NULL;
1409 break;
1410 }
1411 next = rcu_dereference(node->p.next);
1412 if (likely(!is_removed(next))
1413 && !is_dummy(next)) {
1414 break;
1415 }
1416 node = clear_flag(next);
1417 }
1418 assert(!node || !is_dummy(rcu_dereference(node->p.next)));
1419 iter->node = node;
1420 iter->next = next;
1421 }
1422
1423 void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1424 {
1425 struct _cds_lfht_node *lookup;
1426
1427 /*
1428 * Get next after first dummy node. The first dummy node is the
1429 * first node of the linked list.
1430 */
1431 lookup = &ht->t.tbl[0]->nodes[0];
1432 iter->node = (struct cds_lfht_node *) lookup;
1433 cds_lfht_next(ht, iter);
1434 }
1435
1436 void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node)
1437 {
1438 unsigned long hash, size;
1439
1440 hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
1441 node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
1442
1443 size = rcu_dereference(ht->t.size);
1444 (void) _cds_lfht_add(ht, size, node, ADD_DEFAULT, 0);
1445 ht_count_add(ht, size);
1446 }
1447
1448 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
1449 struct cds_lfht_node *node)
1450 {
1451 unsigned long hash, size;
1452 struct cds_lfht_node *ret;
1453
1454 hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
1455 node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
1456
1457 size = rcu_dereference(ht->t.size);
1458 ret = _cds_lfht_add(ht, size, node, ADD_UNIQUE, 0);
1459 if (ret == node)
1460 ht_count_add(ht, size);
1461 return ret;
1462 }
1463
1464 struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
1465 struct cds_lfht_node *node)
1466 {
1467 unsigned long hash, size;
1468 struct cds_lfht_node *ret;
1469
1470 hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
1471 node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
1472
1473 size = rcu_dereference(ht->t.size);
1474 ret = _cds_lfht_add(ht, size, node, ADD_REPLACE, 0);
1475 if (ret == NULL)
1476 ht_count_add(ht, size);
1477 return ret;
1478 }
1479
1480 int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
1481 struct cds_lfht_node *new_node)
1482 {
1483 unsigned long size;
1484
1485 size = rcu_dereference(ht->t.size);
1486 return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next,
1487 new_node);
1488 }
1489
1490 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter)
1491 {
1492 unsigned long size;
1493 int ret;
1494
1495 size = rcu_dereference(ht->t.size);
1496 ret = _cds_lfht_del(ht, size, iter->node, 0);
1497 if (!ret)
1498 ht_count_del(ht, size);
1499 return ret;
1500 }
1501
1502 static
1503 int cds_lfht_delete_dummy(struct cds_lfht *ht)
1504 {
1505 struct cds_lfht_node *node;
1506 struct _cds_lfht_node *lookup;
1507 unsigned long order, i, size;
1508
1509 /* Check that the table is empty */
1510 lookup = &ht->t.tbl[0]->nodes[0];
1511 node = (struct cds_lfht_node *) lookup;
1512 do {
1513 node = clear_flag(node)->p.next;
1514 if (!is_dummy(node))
1515 return -EPERM;
1516 assert(!is_removed(node));
1517 } while (!is_end(node));
1518 /*
1519 * size accessed without rcu_dereference because hash table is
1520 * being destroyed.
1521 */
1522 size = ht->t.size;
1523 /* Internal sanity check: all nodes left should be dummy */
1524 for (order = 0; order < get_count_order_ulong(size) + 1; order++) {
1525 unsigned long len;
1526
1527 len = !order ? 1 : 1UL << (order - 1);
1528 for (i = 0; i < len; i++) {
1529 dbg_printf("delete order %lu i %lu hash %lu\n",
1530 order, i,
1531 bit_reverse_ulong(ht->t.tbl[order]->nodes[i].reverse_hash));
1532 assert(is_dummy(ht->t.tbl[order]->nodes[i].next));
1533 }
1534 poison_free(ht->t.tbl[order]);
1535 }
1536 return 0;
1537 }
1538
1539 /*
1540 * Should only be called when no more concurrent readers nor writers can
1541 * possibly access the table.
1542 */
1543 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
1544 {
1545 int ret;
1546
1547 /* Wait for in-flight resize operations to complete */
1548 CMM_STORE_SHARED(ht->in_progress_destroy, 1);
1549 while (uatomic_read(&ht->in_progress_resize))
1550 poll(NULL, 0, 100); /* wait for 100ms */
1551 ret = cds_lfht_delete_dummy(ht);
1552 if (ret)
1553 return ret;
1554 free_per_cpu_items_count(ht->percpu_count);
1555 if (attr)
1556 *attr = ht->resize_attr;
1557 poison_free(ht);
1558 return ret;
1559 }
1560
1561 void cds_lfht_count_nodes(struct cds_lfht *ht,
1562 long *approx_before,
1563 unsigned long *count,
1564 unsigned long *removed,
1565 long *approx_after)
1566 {
1567 struct cds_lfht_node *node, *next;
1568 struct _cds_lfht_node *lookup;
1569 unsigned long nr_dummy = 0;
1570
1571 *approx_before = 0;
1572 if (nr_cpus_mask >= 0) {
1573 int i;
1574
1575 for (i = 0; i < nr_cpus_mask + 1; i++) {
1576 *approx_before += uatomic_read(&ht->percpu_count[i].add);
1577 *approx_before -= uatomic_read(&ht->percpu_count[i].del);
1578 }
1579 }
1580
1581 *count = 0;
1582 *removed = 0;
1583
1584 /* Count non-dummy nodes in the table */
1585 lookup = &ht->t.tbl[0]->nodes[0];
1586 node = (struct cds_lfht_node *) lookup;
1587 do {
1588 next = rcu_dereference(node->p.next);
1589 if (is_removed(next)) {
1590 if (!is_dummy(next))
1591 (*removed)++;
1592 else
1593 (nr_dummy)++;
1594 } else if (!is_dummy(next))
1595 (*count)++;
1596 else
1597 (nr_dummy)++;
1598 node = clear_flag(next);
1599 } while (!is_end(node));
1600 dbg_printf("number of dummy nodes: %lu\n", nr_dummy);
1601 *approx_after = 0;
1602 if (nr_cpus_mask >= 0) {
1603 int i;
1604
1605 for (i = 0; i < nr_cpus_mask + 1; i++) {
1606 *approx_after += uatomic_read(&ht->percpu_count[i].add);
1607 *approx_after -= uatomic_read(&ht->percpu_count[i].del);
1608 }
1609 }
1610 }
1611
1612 /* called with resize mutex held */
1613 static
1614 void _do_cds_lfht_grow(struct cds_lfht *ht,
1615 unsigned long old_size, unsigned long new_size)
1616 {
1617 unsigned long old_order, new_order;
1618
1619 old_order = get_count_order_ulong(old_size) + 1;
1620 new_order = get_count_order_ulong(new_size) + 1;
1621 printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1622 old_size, old_order, new_size, new_order);
1623 assert(new_size > old_size);
1624 init_table(ht, old_order, new_order - old_order);
1625 }
1626
1627 /* called with resize mutex held */
1628 static
1629 void _do_cds_lfht_shrink(struct cds_lfht *ht,
1630 unsigned long old_size, unsigned long new_size)
1631 {
1632 unsigned long old_order, new_order;
1633
1634 new_size = max(new_size, MIN_TABLE_SIZE);
1635 old_order = get_count_order_ulong(old_size) + 1;
1636 new_order = get_count_order_ulong(new_size) + 1;
1637 printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1638 old_size, old_order, new_size, new_order);
1639 assert(new_size < old_size);
1640
1641 /* Remove and unlink all dummy nodes to remove. */
1642 fini_table(ht, new_order, old_order - new_order);
1643 }
1644
1645
1646 /* called with resize mutex held */
1647 static
1648 void _do_cds_lfht_resize(struct cds_lfht *ht)
1649 {
1650 unsigned long new_size, old_size;
1651
1652 /*
1653 * Resize table, re-do if the target size has changed under us.
1654 */
1655 do {
1656 ht->t.resize_initiated = 1;
1657 old_size = ht->t.size;
1658 new_size = CMM_LOAD_SHARED(ht->t.resize_target);
1659 if (old_size < new_size)
1660 _do_cds_lfht_grow(ht, old_size, new_size);
1661 else if (old_size > new_size)
1662 _do_cds_lfht_shrink(ht, old_size, new_size);
1663 ht->t.resize_initiated = 0;
1664 /* write resize_initiated before read resize_target */
1665 cmm_smp_mb();
1666 } while (ht->t.size != CMM_LOAD_SHARED(ht->t.resize_target));
1667 }
1668
1669 static
1670 unsigned long resize_target_update(struct cds_lfht *ht, unsigned long size,
1671 int growth_order)
1672 {
1673 return _uatomic_max(&ht->t.resize_target,
1674 size << growth_order);
1675 }
1676
1677 static
1678 void resize_target_update_count(struct cds_lfht *ht,
1679 unsigned long count)
1680 {
1681 count = max(count, MIN_TABLE_SIZE);
1682 uatomic_set(&ht->t.resize_target, count);
1683 }
1684
1685 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
1686 {
1687 resize_target_update_count(ht, new_size);
1688 CMM_STORE_SHARED(ht->t.resize_initiated, 1);
1689 ht->cds_lfht_rcu_thread_offline();
1690 pthread_mutex_lock(&ht->resize_mutex);
1691 _do_cds_lfht_resize(ht);
1692 pthread_mutex_unlock(&ht->resize_mutex);
1693 ht->cds_lfht_rcu_thread_online();
1694 }
1695
1696 static
1697 void do_resize_cb(struct rcu_head *head)
1698 {
1699 struct rcu_resize_work *work =
1700 caa_container_of(head, struct rcu_resize_work, head);
1701 struct cds_lfht *ht = work->ht;
1702
1703 ht->cds_lfht_rcu_thread_offline();
1704 pthread_mutex_lock(&ht->resize_mutex);
1705 _do_cds_lfht_resize(ht);
1706 pthread_mutex_unlock(&ht->resize_mutex);
1707 ht->cds_lfht_rcu_thread_online();
1708 poison_free(work);
1709 cmm_smp_mb(); /* finish resize before decrement */
1710 uatomic_dec(&ht->in_progress_resize);
1711 }
1712
1713 static
1714 void cds_lfht_resize_lazy(struct cds_lfht *ht, unsigned long size, int growth)
1715 {
1716 struct rcu_resize_work *work;
1717 unsigned long target_size;
1718
1719 target_size = resize_target_update(ht, size, growth);
1720 /* Store resize_target before read resize_initiated */
1721 cmm_smp_mb();
1722 if (!CMM_LOAD_SHARED(ht->t.resize_initiated) && size < target_size) {
1723 uatomic_inc(&ht->in_progress_resize);
1724 cmm_smp_mb(); /* increment resize count before calling it */
1725 work = malloc(sizeof(*work));
1726 work->ht = ht;
1727 ht->cds_lfht_call_rcu(&work->head, do_resize_cb);
1728 CMM_STORE_SHARED(ht->t.resize_initiated, 1);
1729 }
1730 }
1731
1732 #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
1733
1734 static
1735 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
1736 unsigned long count)
1737 {
1738 struct rcu_resize_work *work;
1739
1740 if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
1741 return;
1742 resize_target_update_count(ht, count);
1743 /* Store resize_target before read resize_initiated */
1744 cmm_smp_mb();
1745 if (!CMM_LOAD_SHARED(ht->t.resize_initiated)) {
1746 uatomic_inc(&ht->in_progress_resize);
1747 cmm_smp_mb(); /* increment resize count before calling it */
1748 work = malloc(sizeof(*work));
1749 work->ht = ht;
1750 ht->cds_lfht_call_rcu(&work->head, do_resize_cb);
1751 CMM_STORE_SHARED(ht->t.resize_initiated, 1);
1752 }
1753 }
1754
1755 #endif
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