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