4 * Userspace RCU library - Lock-Free Resizable RCU Hash Table
6 * Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
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,
32 * Some specificities of this Lock-Free Resizable RCU Hash Table
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
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
54 * - The resize operation for larger tables (and available through an
55 * API) allows both expanding and shrinking the hash table.
56 * - 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
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
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 (except for order 0).
95 * - synchronzie_rcu is used to garbage-collect the old dummy node 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.
102 * hash table hash table the last all dummy node tables
103 * order size dummy node 0 1 2 3 4 5 6(index)
110 * 5 32 16 1 1 2 4 8 16
111 * 6 64 32 1 1 2 4 8 16 32
113 * When growing/shrinking, we only focus on the last dummy node table
114 * which size is (!order ? 1 : (1 << (order -1))).
116 * Example for growing/shrinking:
117 * grow hash table from order 5 to 6: init the index=6 dummy node table
118 * shrink hash table from order 6 to 5: fini the index=6 dummy node table
120 * A bit of ascii art explanation:
122 * Order index is the off-by-one compare to the actual power of 2 because
123 * we use index 0 to deal with the 0 special-case.
125 * This shows the nodes for a small table ordered by reversed bits:
137 * This shows the nodes in order of non-reversed bits, linked by
138 * reversed-bit order.
143 * 2 | | 2 010 010 <- |
144 * | | | 3 011 110 | <- |
145 * 3 -> | | | 4 100 001 | |
161 #include <urcu-call-rcu.h>
162 #include <urcu/arch.h>
163 #include <urcu/uatomic.h>
164 #include <urcu/compiler.h>
168 #include "rculfhash.h"
171 #define dbg_printf(fmt, args...) printf("[debug rculfhash] " fmt, ## args)
173 #define dbg_printf(fmt, args...)
177 * Split-counters lazily update the global counter each 1024
178 * addition/removal. It automatically keeps track of resize required.
179 * We use the bucket length as indicator for need to expand for small
180 * tables and machines lacking per-cpu data suppport.
182 #define COUNT_COMMIT_ORDER 10
183 #define DEFAULT_SPLIT_COUNT_MASK 0xFUL
184 #define CHAIN_LEN_TARGET 1
185 #define CHAIN_LEN_RESIZE_THRESHOLD 3
188 * Define the minimum table size.
190 #define MIN_TABLE_SIZE 1
192 #if (CAA_BITS_PER_LONG == 32)
193 #define MAX_TABLE_ORDER 32
195 #define MAX_TABLE_ORDER 64
199 * Minimum number of dummy nodes to touch per thread to parallelize grow/shrink.
201 #define MIN_PARTITION_PER_THREAD_ORDER 12
202 #define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
205 #define min(a, b) ((a) < (b) ? (a) : (b))
209 #define max(a, b) ((a) > (b) ? (a) : (b))
213 * The removed flag needs to be updated atomically with the pointer.
214 * It indicates that no node must attach to the node scheduled for
215 * removal, and that node garbage collection must be performed.
216 * The dummy flag does not require to be updated atomically with the
217 * pointer, but it is added as a pointer low bit flag to save space.
219 #define REMOVED_FLAG (1UL << 0)
220 #define DUMMY_FLAG (1UL << 1)
221 #define FLAGS_MASK ((1UL << 2) - 1)
223 /* Value of the end pointer. Should not interact with flags. */
224 #define END_VALUE NULL
227 * ht_items_count: Split-counters counting the number of node addition
228 * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
229 * is set at hash table creation.
231 * These are free-running counters, never reset to zero. They count the
232 * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
233 * operations to update the global counter. We choose a power-of-2 value
234 * for the trigger to deal with 32 or 64-bit overflow of the counter.
236 struct ht_items_count
{
237 unsigned long add
, del
;
238 } __attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
241 * rcu_level: Contains the per order-index-level dummy node table. The
242 * size of each dummy node table is half the number of hashes contained
243 * in this order (except for order 0). The minimum allocation size
244 * parameter allows combining the dummy node arrays of the lowermost
245 * levels to improve cache locality for small index orders.
248 /* Note: manually update allocation length when adding a field */
249 struct _cds_lfht_node nodes
[0];
253 * rcu_table: Contains the size and desired new size if a resize
254 * operation is in progress, as well as the statically-sized array of
255 * rcu_level pointers.
258 unsigned long size
; /* always a power of 2, shared (RCU) */
259 unsigned long resize_target
;
260 int resize_initiated
;
261 struct rcu_level
*tbl
[MAX_TABLE_ORDER
];
265 * cds_lfht: Top-level data structure representing a lock-free hash
266 * table. Defined in the implementation file to make it be an opaque
271 cds_lfht_hash_fct hash_fct
;
272 cds_lfht_compare_fct compare_fct
;
273 unsigned long min_alloc_order
;
274 unsigned long min_alloc_size
;
275 unsigned long hash_seed
;
278 * We need to put the work threads offline (QSBR) when taking this
279 * mutex, because we use synchronize_rcu within this mutex critical
280 * section, which waits on read-side critical sections, and could
281 * therefore cause grace-period deadlock if we hold off RCU G.P.
284 pthread_mutex_t resize_mutex
; /* resize mutex: add/del mutex */
285 unsigned int in_progress_resize
, in_progress_destroy
;
286 void (*cds_lfht_call_rcu
)(struct rcu_head
*head
,
287 void (*func
)(struct rcu_head
*head
));
288 void (*cds_lfht_synchronize_rcu
)(void);
289 void (*cds_lfht_rcu_read_lock
)(void);
290 void (*cds_lfht_rcu_read_unlock
)(void);
291 void (*cds_lfht_rcu_thread_offline
)(void);
292 void (*cds_lfht_rcu_thread_online
)(void);
293 void (*cds_lfht_rcu_register_thread
)(void);
294 void (*cds_lfht_rcu_unregister_thread
)(void);
295 pthread_attr_t
*resize_attr
; /* Resize threads attributes */
296 long count
; /* global approximate item count */
297 struct ht_items_count
*split_count
; /* split item count */
301 * rcu_resize_work: Contains arguments passed to RCU worker thread
302 * responsible for performing lazy resize.
304 struct rcu_resize_work
{
305 struct rcu_head head
;
310 * partition_resize_work: Contains arguments passed to worker threads
311 * executing the hash table resize on partitions of the hash table
312 * assigned to each processor's worker thread.
314 struct partition_resize_work
{
317 unsigned long i
, start
, len
;
318 void (*fct
)(struct cds_lfht
*ht
, unsigned long i
,
319 unsigned long start
, unsigned long len
);
323 void _cds_lfht_add(struct cds_lfht
*ht
,
325 struct cds_lfht_node
*node
,
326 struct cds_lfht_iter
*unique_ret
,
330 * Algorithm to reverse bits in a word by lookup table, extended to
333 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
334 * Originally from Public Domain.
337 static const uint8_t BitReverseTable256
[256] =
339 #define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
340 #define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
341 #define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
342 R6(0), R6(2), R6(1), R6(3)
349 uint8_t bit_reverse_u8(uint8_t v
)
351 return BitReverseTable256
[v
];
354 static __attribute__((unused
))
355 uint32_t bit_reverse_u32(uint32_t v
)
357 return ((uint32_t) bit_reverse_u8(v
) << 24) |
358 ((uint32_t) bit_reverse_u8(v
>> 8) << 16) |
359 ((uint32_t) bit_reverse_u8(v
>> 16) << 8) |
360 ((uint32_t) bit_reverse_u8(v
>> 24));
363 static __attribute__((unused
))
364 uint64_t bit_reverse_u64(uint64_t v
)
366 return ((uint64_t) bit_reverse_u8(v
) << 56) |
367 ((uint64_t) bit_reverse_u8(v
>> 8) << 48) |
368 ((uint64_t) bit_reverse_u8(v
>> 16) << 40) |
369 ((uint64_t) bit_reverse_u8(v
>> 24) << 32) |
370 ((uint64_t) bit_reverse_u8(v
>> 32) << 24) |
371 ((uint64_t) bit_reverse_u8(v
>> 40) << 16) |
372 ((uint64_t) bit_reverse_u8(v
>> 48) << 8) |
373 ((uint64_t) bit_reverse_u8(v
>> 56));
377 unsigned long bit_reverse_ulong(unsigned long v
)
379 #if (CAA_BITS_PER_LONG == 32)
380 return bit_reverse_u32(v
);
382 return bit_reverse_u64(v
);
387 * fls: returns the position of the most significant bit.
388 * Returns 0 if no bit is set, else returns the position of the most
389 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
391 #if defined(__i386) || defined(__x86_64)
393 unsigned int fls_u32(uint32_t x
)
401 : "=r" (r
) : "rm" (x
));
407 #if defined(__x86_64)
409 unsigned int fls_u64(uint64_t x
)
417 : "=r" (r
) : "rm" (x
));
424 static __attribute__((unused
))
425 unsigned int fls_u64(uint64_t x
)
432 if (!(x
& 0xFFFFFFFF00000000ULL
)) {
436 if (!(x
& 0xFFFF000000000000ULL
)) {
440 if (!(x
& 0xFF00000000000000ULL
)) {
444 if (!(x
& 0xF000000000000000ULL
)) {
448 if (!(x
& 0xC000000000000000ULL
)) {
452 if (!(x
& 0x8000000000000000ULL
)) {
461 static __attribute__((unused
))
462 unsigned int fls_u32(uint32_t x
)
468 if (!(x
& 0xFFFF0000U
)) {
472 if (!(x
& 0xFF000000U
)) {
476 if (!(x
& 0xF0000000U
)) {
480 if (!(x
& 0xC0000000U
)) {
484 if (!(x
& 0x80000000U
)) {
492 unsigned int fls_ulong(unsigned long x
)
494 #if (CAA_BITS_PER_LONG == 32)
502 * Return the minimum order for which x <= (1UL << order).
503 * Return -1 if x is 0.
505 int get_count_order_u32(uint32_t x
)
510 return fls_u32(x
- 1);
514 * Return the minimum order for which x <= (1UL << order).
515 * Return -1 if x is 0.
517 int get_count_order_ulong(unsigned long x
)
522 return fls_ulong(x
- 1);
526 #define poison_free(ptr) \
529 memset(ptr, 0x42, sizeof(*(ptr))); \
534 #define poison_free(ptr) free(ptr)
538 void cds_lfht_resize_lazy(struct cds_lfht
*ht
, unsigned long size
, int growth
);
541 void cds_lfht_resize_lazy_count(struct cds_lfht
*ht
, unsigned long size
,
542 unsigned long count
);
544 static long nr_cpus_mask
= -1;
545 static long split_count_mask
= -1;
547 #if defined(HAVE_SYSCONF)
548 static void ht_init_nr_cpus_mask(void)
552 maxcpus
= sysconf(_SC_NPROCESSORS_CONF
);
558 * round up number of CPUs to next power of two, so we
559 * can use & for modulo.
561 maxcpus
= 1UL << get_count_order_ulong(maxcpus
);
562 nr_cpus_mask
= maxcpus
- 1;
564 #else /* #if defined(HAVE_SYSCONF) */
565 static void ht_init_nr_cpus_mask(void)
569 #endif /* #else #if defined(HAVE_SYSCONF) */
572 void alloc_split_items_count(struct cds_lfht
*ht
)
574 struct ht_items_count
*count
;
576 if (nr_cpus_mask
== -1) {
577 ht_init_nr_cpus_mask();
578 if (nr_cpus_mask
< 0)
579 split_count_mask
= DEFAULT_SPLIT_COUNT_MASK
;
581 split_count_mask
= nr_cpus_mask
;
584 assert(split_count_mask
>= 0);
586 if (ht
->flags
& CDS_LFHT_ACCOUNTING
) {
587 ht
->split_count
= calloc(split_count_mask
+ 1, sizeof(*count
));
588 assert(ht
->split_count
);
590 ht
->split_count
= NULL
;
595 void free_split_items_count(struct cds_lfht
*ht
)
597 poison_free(ht
->split_count
);
600 #if defined(HAVE_SCHED_GETCPU)
602 int ht_get_split_count_index(unsigned long hash
)
606 assert(split_count_mask
>= 0);
607 cpu
= sched_getcpu();
608 if (caa_unlikely(cpu
< 0))
609 return hash
& split_count_mask
;
611 return cpu
& split_count_mask
;
613 #else /* #if defined(HAVE_SCHED_GETCPU) */
615 int ht_get_split_count_index(unsigned long hash
)
617 return hash
& split_count_mask
;
619 #endif /* #else #if defined(HAVE_SCHED_GETCPU) */
622 void ht_count_add(struct cds_lfht
*ht
, unsigned long size
, unsigned long hash
)
624 unsigned long split_count
;
627 if (caa_unlikely(!ht
->split_count
))
629 index
= ht_get_split_count_index(hash
);
630 split_count
= uatomic_add_return(&ht
->split_count
[index
].add
, 1);
631 if (caa_unlikely(!(split_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))) {
634 dbg_printf("add split count %lu\n", split_count
);
635 count
= uatomic_add_return(&ht
->count
,
636 1UL << COUNT_COMMIT_ORDER
);
638 if (!(count
& (count
- 1))) {
639 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) < size
)
641 dbg_printf("add set global %ld\n", count
);
642 cds_lfht_resize_lazy_count(ht
, size
,
643 count
>> (CHAIN_LEN_TARGET
- 1));
649 void ht_count_del(struct cds_lfht
*ht
, unsigned long size
, unsigned long hash
)
651 unsigned long split_count
;
654 if (caa_unlikely(!ht
->split_count
))
656 index
= ht_get_split_count_index(hash
);
657 split_count
= uatomic_add_return(&ht
->split_count
[index
].del
, 1);
658 if (caa_unlikely(!(split_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))) {
661 dbg_printf("del split count %lu\n", split_count
);
662 count
= uatomic_add_return(&ht
->count
,
663 -(1UL << COUNT_COMMIT_ORDER
));
665 if (!(count
& (count
- 1))) {
666 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) >= size
)
668 dbg_printf("del set global %ld\n", count
);
670 * Don't shrink table if the number of nodes is below a
673 if (count
< (1UL << COUNT_COMMIT_ORDER
) * (split_count_mask
+ 1))
675 cds_lfht_resize_lazy_count(ht
, size
,
676 count
>> (CHAIN_LEN_TARGET
- 1));
682 void check_resize(struct cds_lfht
*ht
, unsigned long size
, uint32_t chain_len
)
686 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
688 count
= uatomic_read(&ht
->count
);
690 * Use bucket-local length for small table expand and for
691 * environments lacking per-cpu data support.
693 if (count
>= (1UL << COUNT_COMMIT_ORDER
))
696 dbg_printf("WARNING: large chain length: %u.\n",
698 if (chain_len
>= CHAIN_LEN_RESIZE_THRESHOLD
)
699 cds_lfht_resize_lazy(ht
, size
,
700 get_count_order_u32(chain_len
- (CHAIN_LEN_TARGET
- 1)));
704 struct cds_lfht_node
*clear_flag(struct cds_lfht_node
*node
)
706 return (struct cds_lfht_node
*) (((unsigned long) node
) & ~FLAGS_MASK
);
710 int is_removed(struct cds_lfht_node
*node
)
712 return ((unsigned long) node
) & REMOVED_FLAG
;
716 struct cds_lfht_node
*flag_removed(struct cds_lfht_node
*node
)
718 return (struct cds_lfht_node
*) (((unsigned long) node
) | REMOVED_FLAG
);
722 int is_dummy(struct cds_lfht_node
*node
)
724 return ((unsigned long) node
) & DUMMY_FLAG
;
728 struct cds_lfht_node
*flag_dummy(struct cds_lfht_node
*node
)
730 return (struct cds_lfht_node
*) (((unsigned long) node
) | DUMMY_FLAG
);
734 struct cds_lfht_node
*get_end(void)
736 return (struct cds_lfht_node
*) END_VALUE
;
740 int is_end(struct cds_lfht_node
*node
)
742 return clear_flag(node
) == (struct cds_lfht_node
*) END_VALUE
;
746 unsigned long _uatomic_max(unsigned long *ptr
, unsigned long v
)
748 unsigned long old1
, old2
;
750 old1
= uatomic_read(ptr
);
755 } while ((old1
= uatomic_cmpxchg(ptr
, old2
, v
)) != old2
);
760 struct _cds_lfht_node
*lookup_bucket(struct cds_lfht
*ht
, unsigned long size
,
763 unsigned long index
, order
;
766 index
= hash
& (size
- 1);
768 if (index
< ht
->min_alloc_size
) {
769 dbg_printf("lookup hash %lu index %lu order 0 aridx 0\n",
771 return &ht
->t
.tbl
[0]->nodes
[index
];
774 * equivalent to get_count_order_ulong(index + 1), but optimizes
775 * away the non-existing 0 special-case for
776 * get_count_order_ulong.
778 order
= fls_ulong(index
);
779 dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
780 hash
, index
, order
, index
& ((1UL << (order
- 1)) - 1));
781 return &ht
->t
.tbl
[order
]->nodes
[index
& ((1UL << (order
- 1)) - 1)];
785 * Remove all logically deleted nodes from a bucket up to a certain node key.
788 void _cds_lfht_gc_bucket(struct cds_lfht_node
*dummy
, struct cds_lfht_node
*node
)
790 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_next
;
792 assert(!is_dummy(dummy
));
793 assert(!is_removed(dummy
));
794 assert(!is_dummy(node
));
795 assert(!is_removed(node
));
798 /* We can always skip the dummy node initially */
799 iter
= rcu_dereference(iter_prev
->p
.next
);
800 assert(!is_removed(iter
));
801 assert(iter_prev
->p
.reverse_hash
<= node
->p
.reverse_hash
);
803 * We should never be called with dummy (start of chain)
804 * and logically removed node (end of path compression
805 * marker) being the actual same node. This would be a
806 * bug in the algorithm implementation.
808 assert(dummy
!= node
);
810 if (caa_unlikely(is_end(iter
)))
812 if (caa_likely(clear_flag(iter
)->p
.reverse_hash
> node
->p
.reverse_hash
))
814 next
= rcu_dereference(clear_flag(iter
)->p
.next
);
815 if (caa_likely(is_removed(next
)))
817 iter_prev
= clear_flag(iter
);
820 assert(!is_removed(iter
));
822 new_next
= flag_dummy(clear_flag(next
));
824 new_next
= clear_flag(next
);
825 (void) uatomic_cmpxchg(&iter_prev
->p
.next
, iter
, new_next
);
831 int _cds_lfht_replace(struct cds_lfht
*ht
, unsigned long size
,
832 struct cds_lfht_node
*old_node
,
833 struct cds_lfht_node
*old_next
,
834 struct cds_lfht_node
*new_node
)
836 struct cds_lfht_node
*dummy
, *ret_next
;
837 struct _cds_lfht_node
*lookup
;
839 if (!old_node
) /* Return -ENOENT if asked to replace NULL node */
842 assert(!is_removed(old_node
));
843 assert(!is_dummy(old_node
));
844 assert(!is_removed(new_node
));
845 assert(!is_dummy(new_node
));
846 assert(new_node
!= old_node
);
848 /* Insert after node to be replaced */
849 if (is_removed(old_next
)) {
851 * Too late, the old node has been removed under us
852 * between lookup and replace. Fail.
856 assert(!is_dummy(old_next
));
857 assert(new_node
!= clear_flag(old_next
));
858 new_node
->p
.next
= clear_flag(old_next
);
860 * Here is the whole trick for lock-free replace: we add
861 * the replacement node _after_ the node we want to
862 * replace by atomically setting its next pointer at the
863 * same time we set its removal flag. Given that
864 * the lookups/get next use an iterator aware of the
865 * next pointer, they will either skip the old node due
866 * to the removal flag and see the new node, or use
867 * the old node, but will not see the new one.
869 ret_next
= uatomic_cmpxchg(&old_node
->p
.next
,
870 old_next
, flag_removed(new_node
));
871 if (ret_next
== old_next
)
872 break; /* We performed the replacement. */
877 * Ensure that the old node is not visible to readers anymore:
878 * lookup for the node, and remove it (along with any other
879 * logically removed node) if found.
881 lookup
= lookup_bucket(ht
, size
, bit_reverse_ulong(old_node
->p
.reverse_hash
));
882 dummy
= (struct cds_lfht_node
*) lookup
;
883 _cds_lfht_gc_bucket(dummy
, new_node
);
885 assert(is_removed(rcu_dereference(old_node
->p
.next
)));
890 * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
891 * mode. A NULL unique_ret allows creation of duplicate keys.
894 void _cds_lfht_add(struct cds_lfht
*ht
,
896 struct cds_lfht_node
*node
,
897 struct cds_lfht_iter
*unique_ret
,
900 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_node
, *new_next
,
902 struct _cds_lfht_node
*lookup
;
904 assert(!is_dummy(node
));
905 assert(!is_removed(node
));
906 lookup
= lookup_bucket(ht
, size
, bit_reverse_ulong(node
->p
.reverse_hash
));
908 uint32_t chain_len
= 0;
911 * iter_prev points to the non-removed node prior to the
914 iter_prev
= (struct cds_lfht_node
*) lookup
;
915 /* We can always skip the dummy node initially */
916 iter
= rcu_dereference(iter_prev
->p
.next
);
917 assert(iter_prev
->p
.reverse_hash
<= node
->p
.reverse_hash
);
919 if (caa_unlikely(is_end(iter
)))
921 if (caa_likely(clear_flag(iter
)->p
.reverse_hash
> node
->p
.reverse_hash
))
924 /* dummy node is the first node of the identical-hash-value chain */
925 if (dummy
&& clear_flag(iter
)->p
.reverse_hash
== node
->p
.reverse_hash
)
928 next
= rcu_dereference(clear_flag(iter
)->p
.next
);
929 if (caa_unlikely(is_removed(next
)))
935 && clear_flag(iter
)->p
.reverse_hash
== node
->p
.reverse_hash
) {
936 struct cds_lfht_iter d_iter
= { .node
= node
, .next
= iter
, };
939 * uniquely adding inserts the node as the first
940 * node of the identical-hash-value node chain.
942 * This semantic ensures no duplicated keys
943 * should ever be observable in the table
944 * (including observe one node by one node
945 * by forward iterations)
947 cds_lfht_next_duplicate(ht
, &d_iter
);
951 *unique_ret
= d_iter
;
955 /* Only account for identical reverse hash once */
956 if (iter_prev
->p
.reverse_hash
!= clear_flag(iter
)->p
.reverse_hash
958 check_resize(ht
, size
, ++chain_len
);
959 iter_prev
= clear_flag(iter
);
964 assert(node
!= clear_flag(iter
));
965 assert(!is_removed(iter_prev
));
966 assert(!is_removed(iter
));
967 assert(iter_prev
!= node
);
969 node
->p
.next
= clear_flag(iter
);
971 node
->p
.next
= flag_dummy(clear_flag(iter
));
973 new_node
= flag_dummy(node
);
976 if (uatomic_cmpxchg(&iter_prev
->p
.next
, iter
,
978 continue; /* retry */
985 assert(!is_removed(iter
));
987 new_next
= flag_dummy(clear_flag(next
));
989 new_next
= clear_flag(next
);
990 (void) uatomic_cmpxchg(&iter_prev
->p
.next
, iter
, new_next
);
995 unique_ret
->node
= return_node
;
996 /* unique_ret->next left unset, never used. */
1001 int _cds_lfht_del(struct cds_lfht
*ht
, unsigned long size
,
1002 struct cds_lfht_node
*node
,
1005 struct cds_lfht_node
*dummy
, *next
, *old
;
1006 struct _cds_lfht_node
*lookup
;
1008 if (!node
) /* Return -ENOENT if asked to delete NULL node */
1011 /* logically delete the node */
1012 assert(!is_dummy(node
));
1013 assert(!is_removed(node
));
1014 old
= rcu_dereference(node
->p
.next
);
1016 struct cds_lfht_node
*new_next
;
1019 if (caa_unlikely(is_removed(next
)))
1022 assert(is_dummy(next
));
1024 assert(!is_dummy(next
));
1025 new_next
= flag_removed(next
);
1026 old
= uatomic_cmpxchg(&node
->p
.next
, next
, new_next
);
1027 } while (old
!= next
);
1028 /* We performed the (logical) deletion. */
1031 * Ensure that the node is not visible to readers anymore: lookup for
1032 * the node, and remove it (along with any other logically removed node)
1035 lookup
= lookup_bucket(ht
, size
, bit_reverse_ulong(node
->p
.reverse_hash
));
1036 dummy
= (struct cds_lfht_node
*) lookup
;
1037 _cds_lfht_gc_bucket(dummy
, node
);
1039 assert(is_removed(rcu_dereference(node
->p
.next
)));
1044 void *partition_resize_thread(void *arg
)
1046 struct partition_resize_work
*work
= arg
;
1048 work
->ht
->cds_lfht_rcu_register_thread();
1049 work
->fct(work
->ht
, work
->i
, work
->start
, work
->len
);
1050 work
->ht
->cds_lfht_rcu_unregister_thread();
1055 void partition_resize_helper(struct cds_lfht
*ht
, unsigned long i
,
1057 void (*fct
)(struct cds_lfht
*ht
, unsigned long i
,
1058 unsigned long start
, unsigned long len
))
1060 unsigned long partition_len
;
1061 struct partition_resize_work
*work
;
1063 unsigned long nr_threads
;
1066 * Note: nr_cpus_mask + 1 is always power of 2.
1067 * We spawn just the number of threads we need to satisfy the minimum
1068 * partition size, up to the number of CPUs in the system.
1070 if (nr_cpus_mask
> 0) {
1071 nr_threads
= min(nr_cpus_mask
+ 1,
1072 len
>> MIN_PARTITION_PER_THREAD_ORDER
);
1076 partition_len
= len
>> get_count_order_ulong(nr_threads
);
1077 work
= calloc(nr_threads
, sizeof(*work
));
1079 for (thread
= 0; thread
< nr_threads
; thread
++) {
1080 work
[thread
].ht
= ht
;
1082 work
[thread
].len
= partition_len
;
1083 work
[thread
].start
= thread
* partition_len
;
1084 work
[thread
].fct
= fct
;
1085 ret
= pthread_create(&(work
[thread
].thread_id
), ht
->resize_attr
,
1086 partition_resize_thread
, &work
[thread
]);
1089 for (thread
= 0; thread
< nr_threads
; thread
++) {
1090 ret
= pthread_join(work
[thread
].thread_id
, NULL
);
1097 * Holding RCU read lock to protect _cds_lfht_add against memory
1098 * reclaim that could be performed by other call_rcu worker threads (ABA
1101 * When we reach a certain length, we can split this population phase over
1102 * many worker threads, based on the number of CPUs available in the system.
1103 * This should therefore take care of not having the expand lagging behind too
1104 * many concurrent insertion threads by using the scheduler's ability to
1105 * schedule dummy node population fairly with insertions.
1108 void init_table_populate_partition(struct cds_lfht
*ht
, unsigned long i
,
1109 unsigned long start
, unsigned long len
)
1113 assert(i
> ht
->min_alloc_order
);
1114 ht
->cds_lfht_rcu_read_lock();
1115 for (j
= start
; j
< start
+ len
; j
++) {
1116 struct cds_lfht_node
*new_node
=
1117 (struct cds_lfht_node
*) &ht
->t
.tbl
[i
]->nodes
[j
];
1119 dbg_printf("init populate: i %lu j %lu hash %lu\n",
1120 i
, j
, (1UL << (i
- 1)) + j
);
1121 new_node
->p
.reverse_hash
=
1122 bit_reverse_ulong((1UL << (i
- 1)) + j
);
1123 _cds_lfht_add(ht
, 1UL << (i
- 1),
1126 ht
->cds_lfht_rcu_read_unlock();
1130 void init_table_populate(struct cds_lfht
*ht
, unsigned long i
,
1133 assert(nr_cpus_mask
!= -1);
1134 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1135 ht
->cds_lfht_rcu_thread_online();
1136 init_table_populate_partition(ht
, i
, 0, len
);
1137 ht
->cds_lfht_rcu_thread_offline();
1140 partition_resize_helper(ht
, i
, len
, init_table_populate_partition
);
1144 void init_table(struct cds_lfht
*ht
,
1145 unsigned long first_order
, unsigned long last_order
)
1149 dbg_printf("init table: first_order %lu last_order %lu\n",
1150 first_order
, last_order
);
1151 assert(first_order
> ht
->min_alloc_order
);
1152 for (i
= first_order
; i
<= last_order
; i
++) {
1155 len
= 1UL << (i
- 1);
1156 dbg_printf("init order %lu len: %lu\n", i
, len
);
1158 /* Stop expand if the resize target changes under us */
1159 if (CMM_LOAD_SHARED(ht
->t
.resize_target
) < (1UL << i
))
1162 ht
->t
.tbl
[i
] = calloc(1, len
* sizeof(struct _cds_lfht_node
));
1163 assert(ht
->t
.tbl
[i
]);
1166 * Set all dummy nodes reverse hash values for a level and
1167 * link all dummy nodes into the table.
1169 init_table_populate(ht
, i
, len
);
1172 * Update table size.
1174 cmm_smp_wmb(); /* populate data before RCU size */
1175 CMM_STORE_SHARED(ht
->t
.size
, 1UL << i
);
1177 dbg_printf("init new size: %lu\n", 1UL << i
);
1178 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1184 * Holding RCU read lock to protect _cds_lfht_remove against memory
1185 * reclaim that could be performed by other call_rcu worker threads (ABA
1187 * For a single level, we logically remove and garbage collect each node.
1189 * As a design choice, we perform logical removal and garbage collection on a
1190 * node-per-node basis to simplify this algorithm. We also assume keeping good
1191 * cache locality of the operation would overweight possible performance gain
1192 * that could be achieved by batching garbage collection for multiple levels.
1193 * However, this would have to be justified by benchmarks.
1195 * Concurrent removal and add operations are helping us perform garbage
1196 * collection of logically removed nodes. We guarantee that all logically
1197 * removed nodes have been garbage-collected (unlinked) before call_rcu is
1198 * invoked to free a hole level of dummy nodes (after a grace period).
1200 * Logical removal and garbage collection can therefore be done in batch or on a
1201 * node-per-node basis, as long as the guarantee above holds.
1203 * When we reach a certain length, we can split this removal over many worker
1204 * threads, based on the number of CPUs available in the system. This should
1205 * take care of not letting resize process lag behind too many concurrent
1206 * updater threads actively inserting into the hash table.
1209 void remove_table_partition(struct cds_lfht
*ht
, unsigned long i
,
1210 unsigned long start
, unsigned long len
)
1214 assert(i
> ht
->min_alloc_order
);
1215 ht
->cds_lfht_rcu_read_lock();
1216 for (j
= start
; j
< start
+ len
; j
++) {
1217 struct cds_lfht_node
*fini_node
=
1218 (struct cds_lfht_node
*) &ht
->t
.tbl
[i
]->nodes
[j
];
1220 dbg_printf("remove entry: i %lu j %lu hash %lu\n",
1221 i
, j
, (1UL << (i
- 1)) + j
);
1222 fini_node
->p
.reverse_hash
=
1223 bit_reverse_ulong((1UL << (i
- 1)) + j
);
1224 (void) _cds_lfht_del(ht
, 1UL << (i
- 1), fini_node
, 1);
1226 ht
->cds_lfht_rcu_read_unlock();
1230 void remove_table(struct cds_lfht
*ht
, unsigned long i
, unsigned long len
)
1233 assert(nr_cpus_mask
!= -1);
1234 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1235 ht
->cds_lfht_rcu_thread_online();
1236 remove_table_partition(ht
, i
, 0, len
);
1237 ht
->cds_lfht_rcu_thread_offline();
1240 partition_resize_helper(ht
, i
, len
, remove_table_partition
);
1244 void fini_table(struct cds_lfht
*ht
,
1245 unsigned long first_order
, unsigned long last_order
)
1248 void *free_by_rcu
= NULL
;
1250 dbg_printf("fini table: first_order %lu last_order %lu\n",
1251 first_order
, last_order
);
1252 assert(first_order
> ht
->min_alloc_order
);
1253 for (i
= last_order
; i
>= first_order
; i
--) {
1256 len
= 1UL << (i
- 1);
1257 dbg_printf("fini order %lu len: %lu\n", i
, len
);
1259 /* Stop shrink if the resize target changes under us */
1260 if (CMM_LOAD_SHARED(ht
->t
.resize_target
) > (1UL << (i
- 1)))
1263 cmm_smp_wmb(); /* populate data before RCU size */
1264 CMM_STORE_SHARED(ht
->t
.size
, 1UL << (i
- 1));
1267 * We need to wait for all add operations to reach Q.S. (and
1268 * thus use the new table for lookups) before we can start
1269 * releasing the old dummy nodes. Otherwise their lookup will
1270 * return a logically removed node as insert position.
1272 ht
->cds_lfht_synchronize_rcu();
1277 * Set "removed" flag in dummy nodes about to be removed.
1278 * Unlink all now-logically-removed dummy node pointers.
1279 * Concurrent add/remove operation are helping us doing
1282 remove_table(ht
, i
, len
);
1284 free_by_rcu
= ht
->t
.tbl
[i
];
1286 dbg_printf("fini new size: %lu\n", 1UL << i
);
1287 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1292 ht
->cds_lfht_synchronize_rcu();
1298 void cds_lfht_create_dummy(struct cds_lfht
*ht
, unsigned long size
)
1300 struct _cds_lfht_node
*prev
, *node
;
1301 unsigned long order
, len
, i
, j
;
1303 ht
->t
.tbl
[0] = calloc(1, ht
->min_alloc_size
* sizeof(struct _cds_lfht_node
));
1304 assert(ht
->t
.tbl
[0]);
1306 dbg_printf("create dummy: order %lu index %lu hash %lu\n", 0, 0, 0);
1307 ht
->t
.tbl
[0]->nodes
[0].next
= flag_dummy(get_end());
1308 ht
->t
.tbl
[0]->nodes
[0].reverse_hash
= 0;
1310 for (order
= 1; order
< get_count_order_ulong(size
) + 1; order
++) {
1311 len
= 1UL << (order
- 1);
1312 if (order
<= ht
->min_alloc_order
) {
1313 ht
->t
.tbl
[order
] = (struct rcu_level
*) (ht
->t
.tbl
[0]->nodes
+ len
);
1315 ht
->t
.tbl
[order
] = calloc(1, len
* sizeof(struct _cds_lfht_node
));
1316 assert(ht
->t
.tbl
[order
]);
1320 prev
= ht
->t
.tbl
[i
]->nodes
;
1321 for (j
= 0; j
< len
; j
++) {
1322 if (j
& (j
- 1)) { /* Between power of 2 */
1324 } else if (j
) { /* At each power of 2 */
1326 prev
= ht
->t
.tbl
[i
]->nodes
;
1329 node
= &ht
->t
.tbl
[order
]->nodes
[j
];
1330 dbg_printf("create dummy: order %lu index %lu hash %lu\n",
1332 node
->next
= prev
->next
;
1333 assert(is_dummy(node
->next
));
1334 node
->reverse_hash
= bit_reverse_ulong(j
+ len
);
1335 prev
->next
= flag_dummy((struct cds_lfht_node
*)node
);
1340 struct cds_lfht
*_cds_lfht_new(cds_lfht_hash_fct hash_fct
,
1341 cds_lfht_compare_fct compare_fct
,
1342 unsigned long hash_seed
,
1343 unsigned long init_size
,
1344 unsigned long min_alloc_size
,
1346 void (*cds_lfht_call_rcu
)(struct rcu_head
*head
,
1347 void (*func
)(struct rcu_head
*head
)),
1348 void (*cds_lfht_synchronize_rcu
)(void),
1349 void (*cds_lfht_rcu_read_lock
)(void),
1350 void (*cds_lfht_rcu_read_unlock
)(void),
1351 void (*cds_lfht_rcu_thread_offline
)(void),
1352 void (*cds_lfht_rcu_thread_online
)(void),
1353 void (*cds_lfht_rcu_register_thread
)(void),
1354 void (*cds_lfht_rcu_unregister_thread
)(void),
1355 pthread_attr_t
*attr
)
1357 struct cds_lfht
*ht
;
1358 unsigned long order
;
1360 /* min_alloc_size must be power of two */
1361 if (!min_alloc_size
|| (min_alloc_size
& (min_alloc_size
- 1)))
1363 /* init_size must be power of two */
1364 if (!init_size
|| (init_size
& (init_size
- 1)))
1366 min_alloc_size
= max(min_alloc_size
, MIN_TABLE_SIZE
);
1367 init_size
= max(init_size
, min_alloc_size
);
1368 ht
= calloc(1, sizeof(struct cds_lfht
));
1371 ht
->hash_fct
= hash_fct
;
1372 ht
->compare_fct
= compare_fct
;
1373 ht
->hash_seed
= hash_seed
;
1374 ht
->cds_lfht_call_rcu
= cds_lfht_call_rcu
;
1375 ht
->cds_lfht_synchronize_rcu
= cds_lfht_synchronize_rcu
;
1376 ht
->cds_lfht_rcu_read_lock
= cds_lfht_rcu_read_lock
;
1377 ht
->cds_lfht_rcu_read_unlock
= cds_lfht_rcu_read_unlock
;
1378 ht
->cds_lfht_rcu_thread_offline
= cds_lfht_rcu_thread_offline
;
1379 ht
->cds_lfht_rcu_thread_online
= cds_lfht_rcu_thread_online
;
1380 ht
->cds_lfht_rcu_register_thread
= cds_lfht_rcu_register_thread
;
1381 ht
->cds_lfht_rcu_unregister_thread
= cds_lfht_rcu_unregister_thread
;
1382 ht
->resize_attr
= attr
;
1383 alloc_split_items_count(ht
);
1384 /* this mutex should not nest in read-side C.S. */
1385 pthread_mutex_init(&ht
->resize_mutex
, NULL
);
1386 order
= get_count_order_ulong(init_size
);
1387 ht
->t
.resize_target
= 1UL << order
;
1388 ht
->min_alloc_size
= min_alloc_size
;
1389 ht
->min_alloc_order
= get_count_order_ulong(min_alloc_size
);
1390 cds_lfht_create_dummy(ht
, 1UL << order
);
1391 ht
->t
.size
= 1UL << order
;
1395 void cds_lfht_lookup(struct cds_lfht
*ht
, void *key
, size_t key_len
,
1396 struct cds_lfht_iter
*iter
)
1398 struct cds_lfht_node
*node
, *next
, *dummy_node
;
1399 struct _cds_lfht_node
*lookup
;
1400 unsigned long hash
, reverse_hash
, size
;
1402 hash
= ht
->hash_fct(key
, key_len
, ht
->hash_seed
);
1403 reverse_hash
= bit_reverse_ulong(hash
);
1405 size
= rcu_dereference(ht
->t
.size
);
1406 lookup
= lookup_bucket(ht
, size
, hash
);
1407 dummy_node
= (struct cds_lfht_node
*) lookup
;
1408 /* We can always skip the dummy node initially */
1409 node
= rcu_dereference(dummy_node
->p
.next
);
1410 node
= clear_flag(node
);
1412 if (caa_unlikely(is_end(node
))) {
1416 if (caa_unlikely(node
->p
.reverse_hash
> reverse_hash
)) {
1420 next
= rcu_dereference(node
->p
.next
);
1421 assert(node
== clear_flag(node
));
1422 if (caa_likely(!is_removed(next
))
1424 && node
->p
.reverse_hash
== reverse_hash
1425 && caa_likely(!ht
->compare_fct(node
->key
, node
->key_len
, key
, key_len
))) {
1428 node
= clear_flag(next
);
1430 assert(!node
|| !is_dummy(rcu_dereference(node
->p
.next
)));
1435 void cds_lfht_next_duplicate(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1437 struct cds_lfht_node
*node
, *next
;
1438 unsigned long reverse_hash
;
1443 reverse_hash
= node
->p
.reverse_hash
;
1445 key_len
= node
->key_len
;
1447 node
= clear_flag(next
);
1450 if (caa_unlikely(is_end(node
))) {
1454 if (caa_unlikely(node
->p
.reverse_hash
> reverse_hash
)) {
1458 next
= rcu_dereference(node
->p
.next
);
1459 if (caa_likely(!is_removed(next
))
1461 && caa_likely(!ht
->compare_fct(node
->key
, node
->key_len
, key
, key_len
))) {
1464 node
= clear_flag(next
);
1466 assert(!node
|| !is_dummy(rcu_dereference(node
->p
.next
)));
1471 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1473 struct cds_lfht_node
*node
, *next
;
1475 node
= clear_flag(iter
->next
);
1477 if (caa_unlikely(is_end(node
))) {
1481 next
= rcu_dereference(node
->p
.next
);
1482 if (caa_likely(!is_removed(next
))
1483 && !is_dummy(next
)) {
1486 node
= clear_flag(next
);
1488 assert(!node
|| !is_dummy(rcu_dereference(node
->p
.next
)));
1493 void cds_lfht_first(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1495 struct _cds_lfht_node
*lookup
;
1498 * Get next after first dummy node. The first dummy node is the
1499 * first node of the linked list.
1501 lookup
= &ht
->t
.tbl
[0]->nodes
[0];
1502 iter
->next
= lookup
->next
;
1503 cds_lfht_next(ht
, iter
);
1506 void cds_lfht_add(struct cds_lfht
*ht
, struct cds_lfht_node
*node
)
1508 unsigned long hash
, size
;
1510 hash
= ht
->hash_fct(node
->key
, node
->key_len
, ht
->hash_seed
);
1511 node
->p
.reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1513 size
= rcu_dereference(ht
->t
.size
);
1514 _cds_lfht_add(ht
, size
, node
, NULL
, 0);
1515 ht_count_add(ht
, size
, hash
);
1518 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
1519 struct cds_lfht_node
*node
)
1521 unsigned long hash
, size
;
1522 struct cds_lfht_iter iter
;
1524 hash
= ht
->hash_fct(node
->key
, node
->key_len
, ht
->hash_seed
);
1525 node
->p
.reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1527 size
= rcu_dereference(ht
->t
.size
);
1528 _cds_lfht_add(ht
, size
, node
, &iter
, 0);
1529 if (iter
.node
== node
)
1530 ht_count_add(ht
, size
, hash
);
1534 struct cds_lfht_node
*cds_lfht_add_replace(struct cds_lfht
*ht
,
1535 struct cds_lfht_node
*node
)
1537 unsigned long hash
, size
;
1538 struct cds_lfht_iter iter
;
1540 hash
= ht
->hash_fct(node
->key
, node
->key_len
, ht
->hash_seed
);
1541 node
->p
.reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1543 size
= rcu_dereference(ht
->t
.size
);
1545 _cds_lfht_add(ht
, size
, node
, &iter
, 0);
1546 if (iter
.node
== node
) {
1547 ht_count_add(ht
, size
, hash
);
1551 if (!_cds_lfht_replace(ht
, size
, iter
.node
, iter
.next
, node
))
1556 int cds_lfht_replace(struct cds_lfht
*ht
, struct cds_lfht_iter
*old_iter
,
1557 struct cds_lfht_node
*new_node
)
1561 size
= rcu_dereference(ht
->t
.size
);
1562 return _cds_lfht_replace(ht
, size
, old_iter
->node
, old_iter
->next
,
1566 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1568 unsigned long size
, hash
;
1571 size
= rcu_dereference(ht
->t
.size
);
1572 ret
= _cds_lfht_del(ht
, size
, iter
->node
, 0);
1574 hash
= bit_reverse_ulong(iter
->node
->p
.reverse_hash
);
1575 ht_count_del(ht
, size
, hash
);
1581 int cds_lfht_delete_dummy(struct cds_lfht
*ht
)
1583 struct cds_lfht_node
*node
;
1584 struct _cds_lfht_node
*lookup
;
1585 unsigned long order
, i
, size
;
1587 /* Check that the table is empty */
1588 lookup
= &ht
->t
.tbl
[0]->nodes
[0];
1589 node
= (struct cds_lfht_node
*) lookup
;
1591 node
= clear_flag(node
)->p
.next
;
1592 if (!is_dummy(node
))
1594 assert(!is_removed(node
));
1595 } while (!is_end(node
));
1597 * size accessed without rcu_dereference because hash table is
1601 /* Internal sanity check: all nodes left should be dummy */
1602 for (order
= 0; order
< get_count_order_ulong(size
) + 1; order
++) {
1605 len
= !order
? 1 : 1UL << (order
- 1);
1606 for (i
= 0; i
< len
; i
++) {
1607 dbg_printf("delete order %lu i %lu hash %lu\n",
1609 bit_reverse_ulong(ht
->t
.tbl
[order
]->nodes
[i
].reverse_hash
));
1610 assert(is_dummy(ht
->t
.tbl
[order
]->nodes
[i
].next
));
1613 if (order
== ht
->min_alloc_order
)
1614 poison_free(ht
->t
.tbl
[0]);
1615 else if (order
> ht
->min_alloc_order
)
1616 poison_free(ht
->t
.tbl
[order
]);
1617 /* Nothing to delete for order < ht->min_alloc_order */
1623 * Should only be called when no more concurrent readers nor writers can
1624 * possibly access the table.
1626 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
)
1630 /* Wait for in-flight resize operations to complete */
1631 _CMM_STORE_SHARED(ht
->in_progress_destroy
, 1);
1632 cmm_smp_mb(); /* Store destroy before load resize */
1633 while (uatomic_read(&ht
->in_progress_resize
))
1634 poll(NULL
, 0, 100); /* wait for 100ms */
1635 ret
= cds_lfht_delete_dummy(ht
);
1638 free_split_items_count(ht
);
1640 *attr
= ht
->resize_attr
;
1645 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
1646 long *approx_before
,
1647 unsigned long *count
,
1648 unsigned long *removed
,
1651 struct cds_lfht_node
*node
, *next
;
1652 struct _cds_lfht_node
*lookup
;
1653 unsigned long nr_dummy
= 0;
1656 if (ht
->split_count
) {
1659 for (i
= 0; i
< split_count_mask
+ 1; i
++) {
1660 *approx_before
+= uatomic_read(&ht
->split_count
[i
].add
);
1661 *approx_before
-= uatomic_read(&ht
->split_count
[i
].del
);
1668 /* Count non-dummy nodes in the table */
1669 lookup
= &ht
->t
.tbl
[0]->nodes
[0];
1670 node
= (struct cds_lfht_node
*) lookup
;
1672 next
= rcu_dereference(node
->p
.next
);
1673 if (is_removed(next
)) {
1674 if (!is_dummy(next
))
1678 } else if (!is_dummy(next
))
1682 node
= clear_flag(next
);
1683 } while (!is_end(node
));
1684 dbg_printf("number of dummy nodes: %lu\n", nr_dummy
);
1686 if (ht
->split_count
) {
1689 for (i
= 0; i
< split_count_mask
+ 1; i
++) {
1690 *approx_after
+= uatomic_read(&ht
->split_count
[i
].add
);
1691 *approx_after
-= uatomic_read(&ht
->split_count
[i
].del
);
1696 /* called with resize mutex held */
1698 void _do_cds_lfht_grow(struct cds_lfht
*ht
,
1699 unsigned long old_size
, unsigned long new_size
)
1701 unsigned long old_order
, new_order
;
1703 old_order
= get_count_order_ulong(old_size
);
1704 new_order
= get_count_order_ulong(new_size
);
1705 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1706 old_size
, old_order
, new_size
, new_order
);
1707 assert(new_size
> old_size
);
1708 init_table(ht
, old_order
+ 1, new_order
);
1711 /* called with resize mutex held */
1713 void _do_cds_lfht_shrink(struct cds_lfht
*ht
,
1714 unsigned long old_size
, unsigned long new_size
)
1716 unsigned long old_order
, new_order
;
1718 new_size
= max(new_size
, ht
->min_alloc_size
);
1719 old_order
= get_count_order_ulong(old_size
);
1720 new_order
= get_count_order_ulong(new_size
);
1721 dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1722 old_size
, old_order
, new_size
, new_order
);
1723 assert(new_size
< old_size
);
1725 /* Remove and unlink all dummy nodes to remove. */
1726 fini_table(ht
, new_order
+ 1, old_order
);
1730 /* called with resize mutex held */
1732 void _do_cds_lfht_resize(struct cds_lfht
*ht
)
1734 unsigned long new_size
, old_size
;
1737 * Resize table, re-do if the target size has changed under us.
1740 assert(uatomic_read(&ht
->in_progress_resize
));
1741 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1743 ht
->t
.resize_initiated
= 1;
1744 old_size
= ht
->t
.size
;
1745 new_size
= CMM_LOAD_SHARED(ht
->t
.resize_target
);
1746 if (old_size
< new_size
)
1747 _do_cds_lfht_grow(ht
, old_size
, new_size
);
1748 else if (old_size
> new_size
)
1749 _do_cds_lfht_shrink(ht
, old_size
, new_size
);
1750 ht
->t
.resize_initiated
= 0;
1751 /* write resize_initiated before read resize_target */
1753 } while (ht
->t
.size
!= CMM_LOAD_SHARED(ht
->t
.resize_target
));
1757 unsigned long resize_target_update(struct cds_lfht
*ht
, unsigned long size
,
1760 return _uatomic_max(&ht
->t
.resize_target
,
1761 size
<< growth_order
);
1765 void resize_target_update_count(struct cds_lfht
*ht
,
1766 unsigned long count
)
1768 count
= max(count
, ht
->min_alloc_size
);
1769 uatomic_set(&ht
->t
.resize_target
, count
);
1772 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
)
1774 resize_target_update_count(ht
, new_size
);
1775 CMM_STORE_SHARED(ht
->t
.resize_initiated
, 1);
1776 ht
->cds_lfht_rcu_thread_offline();
1777 pthread_mutex_lock(&ht
->resize_mutex
);
1778 _do_cds_lfht_resize(ht
);
1779 pthread_mutex_unlock(&ht
->resize_mutex
);
1780 ht
->cds_lfht_rcu_thread_online();
1784 void do_resize_cb(struct rcu_head
*head
)
1786 struct rcu_resize_work
*work
=
1787 caa_container_of(head
, struct rcu_resize_work
, head
);
1788 struct cds_lfht
*ht
= work
->ht
;
1790 ht
->cds_lfht_rcu_thread_offline();
1791 pthread_mutex_lock(&ht
->resize_mutex
);
1792 _do_cds_lfht_resize(ht
);
1793 pthread_mutex_unlock(&ht
->resize_mutex
);
1794 ht
->cds_lfht_rcu_thread_online();
1796 cmm_smp_mb(); /* finish resize before decrement */
1797 uatomic_dec(&ht
->in_progress_resize
);
1801 void cds_lfht_resize_lazy(struct cds_lfht
*ht
, unsigned long size
, int growth
)
1803 struct rcu_resize_work
*work
;
1804 unsigned long target_size
;
1806 target_size
= resize_target_update(ht
, size
, growth
);
1807 /* Store resize_target before read resize_initiated */
1809 if (!CMM_LOAD_SHARED(ht
->t
.resize_initiated
) && size
< target_size
) {
1810 uatomic_inc(&ht
->in_progress_resize
);
1811 cmm_smp_mb(); /* increment resize count before load destroy */
1812 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
)) {
1813 uatomic_dec(&ht
->in_progress_resize
);
1816 work
= malloc(sizeof(*work
));
1818 ht
->cds_lfht_call_rcu(&work
->head
, do_resize_cb
);
1819 CMM_STORE_SHARED(ht
->t
.resize_initiated
, 1);
1824 void cds_lfht_resize_lazy_count(struct cds_lfht
*ht
, unsigned long size
,
1825 unsigned long count
)
1827 struct rcu_resize_work
*work
;
1829 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
1831 resize_target_update_count(ht
, count
);
1832 /* Store resize_target before read resize_initiated */
1834 if (!CMM_LOAD_SHARED(ht
->t
.resize_initiated
)) {
1835 uatomic_inc(&ht
->in_progress_resize
);
1836 cmm_smp_mb(); /* increment resize count before load destroy */
1837 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
)) {
1838 uatomic_dec(&ht
->in_progress_resize
);
1841 work
= malloc(sizeof(*work
));
1843 ht
->cds_lfht_call_rcu(&work
->head
, do_resize_cb
);
1844 CMM_STORE_SHARED(ht
->t
.resize_initiated
, 1);