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 * - Per-CPU Split-counters are used to keep track of the number of
57 * nodes within the hash table for automatic resize triggering.
58 * - Resize operation initiated by long chain detection is executed by a
59 * call_rcu thread, which keeps lock-freedom of add and remove.
60 * - Resize operations are protected by a mutex.
61 * - The removal operation is split in two parts: first, a "removed"
62 * flag is set in the next pointer within the node to remove. Then,
63 * a "garbage collection" is performed in the bucket containing the
64 * removed node (from the start of the bucket up to the removed node).
65 * All encountered nodes with "removed" flag set in their next
66 * pointers are removed from the linked-list. If the cmpxchg used for
67 * removal fails (due to concurrent garbage-collection or concurrent
68 * add), we retry from the beginning of the bucket. This ensures that
69 * the node with "removed" flag set is removed from the hash table
70 * (not visible to lookups anymore) before the RCU read-side critical
71 * section held across removal ends. Furthermore, this ensures that
72 * the node with "removed" flag set is removed from the linked-list
73 * before its memory is reclaimed. Only the thread which removal
74 * successfully set the "removed" flag (with a cmpxchg) into a node's
75 * next pointer is considered to have succeeded its removal (and thus
76 * owns the node to reclaim). Because we garbage-collect starting from
77 * an invariant node (the start-of-bucket dummy node) up to the
78 * "removed" node (or find a reverse-hash that is higher), we are sure
79 * that a successful traversal of the chain leads to a chain that is
80 * present in the linked-list (the start node is never removed) and
81 * that is does not contain the "removed" node anymore, even if
82 * concurrent delete/add operations are changing the structure of the
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
95 * - call_rcu is used to garbage-collect the old order table.
96 * - The per-order dummy node tables contain a compact version of the
97 * hash table nodes. These tables are invariant after they are
98 * populated into the hash table.
100 * A bit of ascii art explanation:
102 * Order index is the off-by-one compare to the actual power of 2 because
103 * we use index 0 to deal with the 0 special-case.
105 * This shows the nodes for a small table ordered by reversed bits:
117 * This shows the nodes in order of non-reversed bits, linked by
118 * reversed-bit order.
123 * 1 | 1 001 100 <- <-
125 * 2 | | 2 010 010 | |
126 * | | | 3 011 110 | <- |
128 * 3 -> | | | 4 100 001 | |
144 #include <urcu-call-rcu.h>
145 #include <urcu/arch.h>
146 #include <urcu/uatomic.h>
147 #include <urcu/jhash.h>
148 #include <urcu/compiler.h>
149 #include <urcu/rculfhash.h>
154 #define dbg_printf(fmt, args...) printf("[debug rculfhash] " fmt, ## args)
156 #define dbg_printf(fmt, args...)
160 * Per-CPU split-counters lazily update the global counter each 1024
161 * addition/removal. It automatically keeps track of resize required.
162 * We use the bucket length as indicator for need to expand for small
163 * tables and machines lacking per-cpu data suppport.
165 #define COUNT_COMMIT_ORDER 10
166 #define CHAIN_LEN_TARGET 1
167 #define CHAIN_LEN_RESIZE_THRESHOLD 3
170 * Define the minimum table size.
172 #define MIN_TABLE_SIZE 1
174 #if (CAA_BITS_PER_LONG == 32)
175 #define MAX_TABLE_ORDER 32
177 #define MAX_TABLE_ORDER 64
181 * Minimum number of dummy nodes to touch per thread to parallelize grow/shrink.
183 #define MIN_PARTITION_PER_THREAD_ORDER 12
184 #define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
187 #define min(a, b) ((a) < (b) ? (a) : (b))
191 #define max(a, b) ((a) > (b) ? (a) : (b))
195 * The removed flag needs to be updated atomically with the pointer.
196 * It indicates that no node must attach to the node scheduled for
197 * removal. The gc flag also needs to be updated atomically with the
198 * pointer. It indicates that node garbage collection must be performed.
199 * The dummy flag does not require to be updated atomically with the
200 * pointer, but it is added as a pointer low bit flag to save space.
202 #define REMOVED_FLAG (1UL << 0)
203 #define GC_FLAG (1UL << 1)
204 #define DUMMY_FLAG (1UL << 2)
205 #define FLAGS_MASK ((1UL << 3) - 1)
207 /* Value of the end pointer. Should not interact with flags. */
208 #define END_VALUE NULL
210 struct ht_items_count
{
211 unsigned long add
, del
;
212 } __attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
215 struct rcu_head head
;
216 struct _cds_lfht_node nodes
[0];
220 unsigned long size
; /* always a power of 2, shared (RCU) */
221 unsigned long resize_target
;
222 int resize_initiated
;
223 struct rcu_level
*tbl
[MAX_TABLE_ORDER
];
228 cds_lfht_hash_fct hash_fct
;
229 cds_lfht_compare_fct compare_fct
;
230 unsigned long hash_seed
;
233 * We need to put the work threads offline (QSBR) when taking this
234 * mutex, because we use synchronize_rcu within this mutex critical
235 * section, which waits on read-side critical sections, and could
236 * therefore cause grace-period deadlock if we hold off RCU G.P.
239 pthread_mutex_t resize_mutex
; /* resize mutex: add/del mutex */
240 unsigned int in_progress_resize
, in_progress_destroy
;
241 void (*cds_lfht_call_rcu
)(struct rcu_head
*head
,
242 void (*func
)(struct rcu_head
*head
));
243 void (*cds_lfht_synchronize_rcu
)(void);
244 void (*cds_lfht_rcu_read_lock
)(void);
245 void (*cds_lfht_rcu_read_unlock
)(void);
246 void (*cds_lfht_rcu_thread_offline
)(void);
247 void (*cds_lfht_rcu_thread_online
)(void);
248 void (*cds_lfht_rcu_register_thread
)(void);
249 void (*cds_lfht_rcu_unregister_thread
)(void);
250 pthread_attr_t
*resize_attr
; /* Resize threads attributes */
251 unsigned long count
; /* global approximate item count */
252 struct ht_items_count
*percpu_count
; /* per-cpu item count */
255 struct rcu_resize_work
{
256 struct rcu_head head
;
260 struct partition_resize_work
{
261 struct rcu_head head
;
263 unsigned long i
, start
, len
;
264 void (*fct
)(struct cds_lfht
*ht
, unsigned long i
,
265 unsigned long start
, unsigned long len
);
275 struct cds_lfht_node
*_cds_lfht_add(struct cds_lfht
*ht
,
277 struct cds_lfht_node
*node
,
278 enum add_mode mode
, int dummy
);
281 int _cds_lfht_del(struct cds_lfht
*ht
, unsigned long size
,
282 struct cds_lfht_node
*node
,
283 int dummy_removal
, int do_gc
);
286 * Algorithm to reverse bits in a word by lookup table, extended to
289 * http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
290 * Originally from Public Domain.
293 static const uint8_t BitReverseTable256
[256] =
295 #define R2(n) (n), (n) + 2*64, (n) + 1*64, (n) + 3*64
296 #define R4(n) R2(n), R2((n) + 2*16), R2((n) + 1*16), R2((n) + 3*16)
297 #define R6(n) R4(n), R4((n) + 2*4 ), R4((n) + 1*4 ), R4((n) + 3*4 )
298 R6(0), R6(2), R6(1), R6(3)
305 uint8_t bit_reverse_u8(uint8_t v
)
307 return BitReverseTable256
[v
];
310 static __attribute__((unused
))
311 uint32_t bit_reverse_u32(uint32_t v
)
313 return ((uint32_t) bit_reverse_u8(v
) << 24) |
314 ((uint32_t) bit_reverse_u8(v
>> 8) << 16) |
315 ((uint32_t) bit_reverse_u8(v
>> 16) << 8) |
316 ((uint32_t) bit_reverse_u8(v
>> 24));
319 static __attribute__((unused
))
320 uint64_t bit_reverse_u64(uint64_t v
)
322 return ((uint64_t) bit_reverse_u8(v
) << 56) |
323 ((uint64_t) bit_reverse_u8(v
>> 8) << 48) |
324 ((uint64_t) bit_reverse_u8(v
>> 16) << 40) |
325 ((uint64_t) bit_reverse_u8(v
>> 24) << 32) |
326 ((uint64_t) bit_reverse_u8(v
>> 32) << 24) |
327 ((uint64_t) bit_reverse_u8(v
>> 40) << 16) |
328 ((uint64_t) bit_reverse_u8(v
>> 48) << 8) |
329 ((uint64_t) bit_reverse_u8(v
>> 56));
333 unsigned long bit_reverse_ulong(unsigned long v
)
335 #if (CAA_BITS_PER_LONG == 32)
336 return bit_reverse_u32(v
);
338 return bit_reverse_u64(v
);
343 * fls: returns the position of the most significant bit.
344 * Returns 0 if no bit is set, else returns the position of the most
345 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
347 #if defined(__i386) || defined(__x86_64)
349 unsigned int fls_u32(uint32_t x
)
357 : "=r" (r
) : "rm" (x
));
363 #if defined(__x86_64)
365 unsigned int fls_u64(uint64_t x
)
373 : "=r" (r
) : "rm" (x
));
380 static __attribute__((unused
))
381 unsigned int fls_u64(uint64_t x
)
388 if (!(x
& 0xFFFFFFFF00000000ULL
)) {
392 if (!(x
& 0xFFFF000000000000ULL
)) {
396 if (!(x
& 0xFF00000000000000ULL
)) {
400 if (!(x
& 0xF000000000000000ULL
)) {
404 if (!(x
& 0xC000000000000000ULL
)) {
408 if (!(x
& 0x8000000000000000ULL
)) {
417 static __attribute__((unused
))
418 unsigned int fls_u32(uint32_t x
)
424 if (!(x
& 0xFFFF0000U
)) {
428 if (!(x
& 0xFF000000U
)) {
432 if (!(x
& 0xF0000000U
)) {
436 if (!(x
& 0xC0000000U
)) {
440 if (!(x
& 0x80000000U
)) {
448 unsigned int fls_ulong(unsigned long x
)
450 #if (CAA_BITS_PER_lONG == 32)
457 int get_count_order_u32(uint32_t x
)
461 order
= fls_u32(x
) - 1;
467 int get_count_order_ulong(unsigned long x
)
471 order
= fls_ulong(x
) - 1;
478 #define poison_free(ptr) \
480 memset(ptr, 0x42, sizeof(*(ptr))); \
484 #define poison_free(ptr) free(ptr)
488 void cds_lfht_resize_lazy(struct cds_lfht
*ht
, unsigned long size
, int growth
);
491 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
492 * available, then we support hash table item accounting.
493 * In the unfortunate event the number of CPUs reported would be
494 * inaccurate, we use modulo arithmetic on the number of CPUs we got.
496 #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
499 void cds_lfht_resize_lazy_count(struct cds_lfht
*ht
, unsigned long size
,
500 unsigned long count
);
502 static long nr_cpus_mask
= -1;
505 struct ht_items_count
*alloc_per_cpu_items_count(void)
507 struct ht_items_count
*count
;
509 switch (nr_cpus_mask
) {
516 maxcpus
= sysconf(_SC_NPROCESSORS_CONF
);
522 * round up number of CPUs to next power of two, so we
523 * can use & for modulo.
525 maxcpus
= 1UL << get_count_order_ulong(maxcpus
);
526 nr_cpus_mask
= maxcpus
- 1;
530 return calloc(nr_cpus_mask
+ 1, sizeof(*count
));
535 void free_per_cpu_items_count(struct ht_items_count
*count
)
545 assert(nr_cpus_mask
>= 0);
546 cpu
= sched_getcpu();
547 if (unlikely(cpu
< 0))
550 return cpu
& nr_cpus_mask
;
554 void ht_count_add(struct cds_lfht
*ht
, unsigned long size
)
556 unsigned long percpu_count
;
559 if (unlikely(!ht
->percpu_count
))
562 if (unlikely(cpu
< 0))
564 percpu_count
= uatomic_add_return(&ht
->percpu_count
[cpu
].add
, 1);
565 if (unlikely(!(percpu_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))) {
568 dbg_printf("add percpu %lu\n", percpu_count
);
569 count
= uatomic_add_return(&ht
->count
,
570 1UL << COUNT_COMMIT_ORDER
);
572 if (!(count
& (count
- 1))) {
573 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) < size
)
575 dbg_printf("add set global %lu\n", count
);
576 cds_lfht_resize_lazy_count(ht
, size
,
577 count
>> (CHAIN_LEN_TARGET
- 1));
583 void ht_count_del(struct cds_lfht
*ht
, unsigned long size
)
585 unsigned long percpu_count
;
588 if (unlikely(!ht
->percpu_count
))
591 if (unlikely(cpu
< 0))
593 percpu_count
= uatomic_add_return(&ht
->percpu_count
[cpu
].del
, -1);
594 if (unlikely(!(percpu_count
& ((1UL << COUNT_COMMIT_ORDER
) - 1)))) {
597 dbg_printf("del percpu %lu\n", percpu_count
);
598 count
= uatomic_add_return(&ht
->count
,
599 -(1UL << COUNT_COMMIT_ORDER
));
601 if (!(count
& (count
- 1))) {
602 if ((count
>> CHAIN_LEN_RESIZE_THRESHOLD
) >= size
)
604 dbg_printf("del set global %lu\n", count
);
605 cds_lfht_resize_lazy_count(ht
, size
,
606 count
>> (CHAIN_LEN_TARGET
- 1));
611 #else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
613 static const long nr_cpus_mask
= -1;
616 struct ht_items_count
*alloc_per_cpu_items_count(void)
622 void free_per_cpu_items_count(struct ht_items_count
*count
)
627 void ht_count_add(struct cds_lfht
*ht
, unsigned long size
)
632 void ht_count_del(struct cds_lfht
*ht
, unsigned long size
)
636 #endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
640 void check_resize(struct cds_lfht
*ht
, unsigned long size
, uint32_t chain_len
)
644 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
646 count
= uatomic_read(&ht
->count
);
648 * Use bucket-local length for small table expand and for
649 * environments lacking per-cpu data support.
651 if (count
>= (1UL << COUNT_COMMIT_ORDER
))
654 dbg_printf("WARNING: large chain length: %u.\n",
656 if (chain_len
>= CHAIN_LEN_RESIZE_THRESHOLD
)
657 cds_lfht_resize_lazy(ht
, size
,
658 get_count_order_u32(chain_len
- (CHAIN_LEN_TARGET
- 1)));
662 struct cds_lfht_node
*clear_flag(struct cds_lfht_node
*node
)
664 return (struct cds_lfht_node
*) (((unsigned long) node
) & ~FLAGS_MASK
);
668 int is_removed(struct cds_lfht_node
*node
)
670 return ((unsigned long) node
) & REMOVED_FLAG
;
674 struct cds_lfht_node
*flag_removed(struct cds_lfht_node
*node
)
676 return (struct cds_lfht_node
*) (((unsigned long) node
) | REMOVED_FLAG
);
680 int is_gc(struct cds_lfht_node
*node
)
682 return ((unsigned long) node
) & GC_FLAG
;
686 struct cds_lfht_node
*flag_gc(struct cds_lfht_node
*node
)
688 return (struct cds_lfht_node
*) (((unsigned long) node
) | GC_FLAG
);
692 int is_dummy(struct cds_lfht_node
*node
)
694 return ((unsigned long) node
) & DUMMY_FLAG
;
698 struct cds_lfht_node
*flag_dummy(struct cds_lfht_node
*node
)
700 return (struct cds_lfht_node
*) (((unsigned long) node
) | DUMMY_FLAG
);
704 struct cds_lfht_node
*get_end(void)
706 return (struct cds_lfht_node
*) END_VALUE
;
710 int is_end(struct cds_lfht_node
*node
)
712 return clear_flag(node
) == (struct cds_lfht_node
*) END_VALUE
;
716 unsigned long _uatomic_max(unsigned long *ptr
, unsigned long v
)
718 unsigned long old1
, old2
;
720 old1
= uatomic_read(ptr
);
725 } while ((old1
= uatomic_cmpxchg(ptr
, old2
, v
)) != old2
);
730 void cds_lfht_free_level(struct rcu_head
*head
)
732 struct rcu_level
*l
=
733 caa_container_of(head
, struct rcu_level
, head
);
738 * Remove all logically deleted nodes from a bucket up to a certain node key.
741 void _cds_lfht_gc_bucket(struct cds_lfht_node
*dummy
, struct cds_lfht_node
*node
)
743 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_next
;
745 assert(!is_dummy(dummy
));
746 assert(!is_gc(dummy
));
747 assert(!is_removed(dummy
));
748 assert(!is_dummy(node
));
749 assert(!is_gc(node
));
750 assert(!is_removed(node
));
753 /* We can always skip the dummy node initially */
754 iter
= rcu_dereference(iter_prev
->p
.next
);
755 assert(iter_prev
->p
.reverse_hash
<= node
->p
.reverse_hash
);
757 * We should never be called with dummy (start of chain)
758 * and logically removed node (end of path compression
759 * marker) being the actual same node. This would be a
760 * bug in the algorithm implementation.
762 assert(dummy
!= node
);
764 if (unlikely(is_end(iter
)))
766 if (likely(clear_flag(iter
)->p
.reverse_hash
> node
->p
.reverse_hash
))
768 next
= rcu_dereference(clear_flag(iter
)->p
.next
);
769 if (likely(is_gc(next
)))
771 iter_prev
= clear_flag(iter
);
774 assert(!is_gc(iter
));
776 new_next
= flag_dummy(clear_flag(next
));
778 new_next
= clear_flag(next
);
779 if (is_removed(iter
))
780 new_next
= flag_removed(new_next
);
781 (void) uatomic_cmpxchg(&iter_prev
->p
.next
, iter
, new_next
);
787 struct cds_lfht_node
*_cds_lfht_add(struct cds_lfht
*ht
,
789 struct cds_lfht_node
*node
,
790 enum add_mode mode
, int dummy
)
792 struct cds_lfht_node
*iter_prev
, *iter
, *next
, *new_node
, *new_next
,
793 *dummy_node
, *return_node
;
794 struct _cds_lfht_node
*lookup
;
795 unsigned long hash
, index
, order
;
797 assert(!is_dummy(node
));
798 assert(!is_gc(node
));
799 assert(!is_removed(node
));
802 node
->p
.next
= flag_dummy(get_end());
803 return node
; /* Initial first add (head) */
805 hash
= bit_reverse_ulong(node
->p
.reverse_hash
);
807 uint32_t chain_len
= 0;
810 * iter_prev points to the non-removed node prior to the
813 index
= hash
& (size
- 1);
814 order
= get_count_order_ulong(index
+ 1);
815 lookup
= &ht
->t
.tbl
[order
]->nodes
[index
& ((!order
? 0 : (1UL << (order
- 1))) - 1)];
816 iter_prev
= (struct cds_lfht_node
*) lookup
;
817 /* We can always skip the dummy node initially */
818 iter
= rcu_dereference(iter_prev
->p
.next
);
819 assert(iter_prev
->p
.reverse_hash
<= node
->p
.reverse_hash
);
821 if (unlikely(is_end(iter
)))
823 if (likely(clear_flag(iter
)->p
.reverse_hash
> node
->p
.reverse_hash
))
825 next
= rcu_dereference(clear_flag(iter
)->p
.next
);
826 if (unlikely(is_gc(next
)))
828 assert(!is_removed(next
));
829 if ((mode
== ADD_UNIQUE
|| mode
== ADD_REPLACE
)
831 && !ht
->compare_fct(node
->key
, node
->key_len
,
832 clear_flag(iter
)->key
,
833 clear_flag(iter
)->key_len
)) {
834 if (mode
== ADD_UNIQUE
)
835 return clear_flag(iter
);
836 else /* mode == ADD_REPLACE */
839 /* Only account for identical reverse hash once */
840 if (iter_prev
->p
.reverse_hash
!= clear_flag(iter
)->p
.reverse_hash
842 check_resize(ht
, size
, ++chain_len
);
843 iter_prev
= clear_flag(iter
);
848 assert(node
!= clear_flag(iter
));
849 assert(!is_removed(iter_prev
));
850 assert(!is_removed(iter
));
851 assert(!is_gc(iter_prev
));
852 assert(!is_gc(iter
));
853 assert(iter_prev
!= node
);
855 node
->p
.next
= clear_flag(iter
);
857 node
->p
.next
= flag_dummy(clear_flag(iter
));
859 new_node
= flag_dummy(node
);
862 if (uatomic_cmpxchg(&iter_prev
->p
.next
, iter
,
864 continue; /* retry */
866 if (mode
== ADD_REPLACE
)
868 else /* ADD_DEFAULT and ADD_UNIQUE */
874 /* Insert after node to be replaced */
875 iter_prev
= clear_flag(iter
);
877 assert(node
!= clear_flag(iter
));
878 assert(!is_removed(iter_prev
));
879 assert(!is_removed(iter
));
880 assert(!is_gc(iter_prev
));
881 assert(!is_gc(iter
));
882 assert(iter_prev
!= node
);
884 node
->p
.next
= clear_flag(iter
);
886 new_node
= flag_dummy(node
);
890 * Here is the whole trick for lock-free replace: we add
891 * the replacement node _after_ the node we want to
892 * replace by atomically setting its next pointer at the
893 * same time we set its removal and gc flags. Given that
894 * the lookups/get next use an iterator aware of the
895 * next pointer, they will either skip the old node due
896 * to the removal/gc flag and see the new node, or use
897 * the old new, but will not see the new one.
899 new_node
= flag_removed(new_node
);
900 new_node
= flag_gc(new_node
);
901 if (uatomic_cmpxchg(&iter_prev
->p
.next
,
902 iter
, new_node
) != iter
) {
903 continue; /* retry */
905 return_node
= iter_prev
;
910 assert(!is_removed(iter
));
911 assert(!is_gc(iter
));
913 new_next
= flag_dummy(clear_flag(next
));
915 new_next
= clear_flag(next
);
916 (void) uatomic_cmpxchg(&iter_prev
->p
.next
, iter
, new_next
);
920 /* Garbage collect logically removed nodes in the bucket */
921 index
= hash
& (size
- 1);
922 order
= get_count_order_ulong(index
+ 1);
923 lookup
= &ht
->t
.tbl
[order
]->nodes
[index
& (!order
? 0 : ((1UL << (order
- 1)) - 1))];
924 dummy_node
= (struct cds_lfht_node
*) lookup
;
925 _cds_lfht_gc_bucket(dummy_node
, node
);
930 int _cds_lfht_del(struct cds_lfht
*ht
, unsigned long size
,
931 struct cds_lfht_node
*node
,
932 int dummy_removal
, int do_gc
)
934 struct cds_lfht_node
*dummy
, *next
, *old
;
935 struct _cds_lfht_node
*lookup
;
937 unsigned long hash
, index
, order
;
939 /* logically delete the node */
940 assert(!is_dummy(node
));
941 assert(!is_gc(node
));
942 assert(!is_removed(node
));
943 old
= rcu_dereference(node
->p
.next
);
945 struct cds_lfht_node
*new_next
;
948 if (unlikely(is_removed(next
)))
951 assert(is_dummy(next
));
953 assert(!is_dummy(next
));
954 new_next
= flag_removed(next
);
956 new_next
= flag_gc(new_next
);
957 old
= uatomic_cmpxchg(&node
->p
.next
, next
, new_next
);
958 } while (old
!= next
);
960 /* We performed the (logical) deletion. */
967 * Ensure that the node is not visible to readers anymore: lookup for
968 * the node, and remove it (along with any other logically removed node)
971 hash
= bit_reverse_ulong(node
->p
.reverse_hash
);
973 index
= hash
& (size
- 1);
974 order
= get_count_order_ulong(index
+ 1);
975 lookup
= &ht
->t
.tbl
[order
]->nodes
[index
& (!order
? 0 : ((1UL << (order
- 1)) - 1))];
976 dummy
= (struct cds_lfht_node
*) lookup
;
977 _cds_lfht_gc_bucket(dummy
, node
);
980 * Only the flagging action indicated that we (and no other)
981 * removed the node from the hash.
984 assert(is_removed(rcu_dereference(node
->p
.next
)));
991 void *partition_resize_thread(void *arg
)
993 struct partition_resize_work
*work
= arg
;
995 work
->ht
->cds_lfht_rcu_register_thread();
996 work
->fct(work
->ht
, work
->i
, work
->start
, work
->len
);
997 work
->ht
->cds_lfht_rcu_unregister_thread();
1002 void partition_resize_helper(struct cds_lfht
*ht
, unsigned long i
,
1004 void (*fct
)(struct cds_lfht
*ht
, unsigned long i
,
1005 unsigned long start
, unsigned long len
))
1007 unsigned long partition_len
;
1008 struct partition_resize_work
*work
;
1010 unsigned long nr_threads
;
1011 pthread_t
*thread_id
;
1014 * Note: nr_cpus_mask + 1 is always power of 2.
1015 * We spawn just the number of threads we need to satisfy the minimum
1016 * partition size, up to the number of CPUs in the system.
1018 nr_threads
= min(nr_cpus_mask
+ 1,
1019 len
>> MIN_PARTITION_PER_THREAD_ORDER
);
1020 partition_len
= len
>> get_count_order_ulong(nr_threads
);
1021 work
= calloc(nr_threads
, sizeof(*work
));
1022 thread_id
= calloc(nr_threads
, sizeof(*thread_id
));
1024 for (thread
= 0; thread
< nr_threads
; thread
++) {
1025 work
[thread
].ht
= ht
;
1027 work
[thread
].len
= partition_len
;
1028 work
[thread
].start
= thread
* partition_len
;
1029 work
[thread
].fct
= fct
;
1030 ret
= pthread_create(&thread_id
[thread
], ht
->resize_attr
,
1031 partition_resize_thread
, &work
[thread
]);
1034 for (thread
= 0; thread
< nr_threads
; thread
++) {
1035 ret
= pthread_join(thread_id
[thread
], NULL
);
1043 * Holding RCU read lock to protect _cds_lfht_add against memory
1044 * reclaim that could be performed by other call_rcu worker threads (ABA
1047 * When we reach a certain length, we can split this population phase over
1048 * many worker threads, based on the number of CPUs available in the system.
1049 * This should therefore take care of not having the expand lagging behind too
1050 * many concurrent insertion threads by using the scheduler's ability to
1051 * schedule dummy node population fairly with insertions.
1054 void init_table_populate_partition(struct cds_lfht
*ht
, unsigned long i
,
1055 unsigned long start
, unsigned long len
)
1059 ht
->cds_lfht_rcu_read_lock();
1060 for (j
= start
; j
< start
+ len
; j
++) {
1061 struct cds_lfht_node
*new_node
=
1062 (struct cds_lfht_node
*) &ht
->t
.tbl
[i
]->nodes
[j
];
1064 dbg_printf("init populate: i %lu j %lu hash %lu\n",
1065 i
, j
, !i
? 0 : (1UL << (i
- 1)) + j
);
1066 new_node
->p
.reverse_hash
=
1067 bit_reverse_ulong(!i
? 0 : (1UL << (i
- 1)) + j
);
1068 (void) _cds_lfht_add(ht
, !i
? 0 : (1UL << (i
- 1)),
1069 new_node
, ADD_DEFAULT
, 1);
1070 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1073 ht
->cds_lfht_rcu_read_unlock();
1077 void init_table_populate(struct cds_lfht
*ht
, unsigned long i
,
1080 assert(nr_cpus_mask
!= -1);
1081 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1082 ht
->cds_lfht_rcu_thread_online();
1083 init_table_populate_partition(ht
, i
, 0, len
);
1084 ht
->cds_lfht_rcu_thread_offline();
1087 partition_resize_helper(ht
, i
, len
, init_table_populate_partition
);
1091 void init_table(struct cds_lfht
*ht
,
1092 unsigned long first_order
, unsigned long len_order
)
1094 unsigned long i
, end_order
;
1096 dbg_printf("init table: first_order %lu end_order %lu\n",
1097 first_order
, first_order
+ len_order
);
1098 end_order
= first_order
+ len_order
;
1099 for (i
= first_order
; i
< end_order
; i
++) {
1102 len
= !i
? 1 : 1UL << (i
- 1);
1103 dbg_printf("init order %lu len: %lu\n", i
, len
);
1105 /* Stop expand if the resize target changes under us */
1106 if (CMM_LOAD_SHARED(ht
->t
.resize_target
) < (!i
? 1 : (1UL << i
)))
1109 ht
->t
.tbl
[i
] = calloc(1, sizeof(struct rcu_level
)
1110 + (len
* sizeof(struct _cds_lfht_node
)));
1111 assert(ht
->t
.tbl
[i
]);
1114 * Set all dummy nodes reverse hash values for a level and
1115 * link all dummy nodes into the table.
1117 init_table_populate(ht
, i
, len
);
1120 * Update table size.
1122 cmm_smp_wmb(); /* populate data before RCU size */
1123 CMM_STORE_SHARED(ht
->t
.size
, !i
? 1 : (1UL << i
));
1125 dbg_printf("init new size: %lu\n", !i
? 1 : (1UL << i
));
1126 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1132 * Holding RCU read lock to protect _cds_lfht_remove against memory
1133 * reclaim that could be performed by other call_rcu worker threads (ABA
1135 * For a single level, we logically remove and garbage collect each node.
1137 * As a design choice, we perform logical removal and garbage collection on a
1138 * node-per-node basis to simplify this algorithm. We also assume keeping good
1139 * cache locality of the operation would overweight possible performance gain
1140 * that could be achieved by batching garbage collection for multiple levels.
1141 * However, this would have to be justified by benchmarks.
1143 * Concurrent removal and add operations are helping us perform garbage
1144 * collection of logically removed nodes. We guarantee that all logically
1145 * removed nodes have been garbage-collected (unlinked) before call_rcu is
1146 * invoked to free a hole level of dummy nodes (after a grace period).
1148 * Logical removal and garbage collection can therefore be done in batch or on a
1149 * node-per-node basis, as long as the guarantee above holds.
1151 * When we reach a certain length, we can split this removal over many worker
1152 * threads, based on the number of CPUs available in the system. This should
1153 * take care of not letting resize process lag behind too many concurrent
1154 * updater threads actively inserting into the hash table.
1157 void remove_table_partition(struct cds_lfht
*ht
, unsigned long i
,
1158 unsigned long start
, unsigned long len
)
1162 ht
->cds_lfht_rcu_read_lock();
1163 for (j
= start
; j
< start
+ len
; j
++) {
1164 struct cds_lfht_node
*fini_node
=
1165 (struct cds_lfht_node
*) &ht
->t
.tbl
[i
]->nodes
[j
];
1167 dbg_printf("remove entry: i %lu j %lu hash %lu\n",
1168 i
, j
, !i
? 0 : (1UL << (i
- 1)) + j
);
1169 fini_node
->p
.reverse_hash
=
1170 bit_reverse_ulong(!i
? 0 : (1UL << (i
- 1)) + j
);
1171 (void) _cds_lfht_del(ht
, !i
? 0 : (1UL << (i
- 1)),
1173 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1176 ht
->cds_lfht_rcu_read_unlock();
1180 void remove_table(struct cds_lfht
*ht
, unsigned long i
, unsigned long len
)
1183 assert(nr_cpus_mask
!= -1);
1184 if (nr_cpus_mask
< 0 || len
< 2 * MIN_PARTITION_PER_THREAD
) {
1185 ht
->cds_lfht_rcu_thread_online();
1186 remove_table_partition(ht
, i
, 0, len
);
1187 ht
->cds_lfht_rcu_thread_offline();
1190 partition_resize_helper(ht
, i
, len
, remove_table_partition
);
1194 void fini_table(struct cds_lfht
*ht
,
1195 unsigned long first_order
, unsigned long len_order
)
1199 dbg_printf("fini table: first_order %lu end_order %lu\n",
1200 first_order
, first_order
+ len_order
);
1201 end_order
= first_order
+ len_order
;
1202 assert(first_order
> 0);
1203 for (i
= end_order
- 1; i
>= first_order
; i
--) {
1206 len
= !i
? 1 : 1UL << (i
- 1);
1207 dbg_printf("fini order %lu len: %lu\n", i
, len
);
1209 /* Stop shrink if the resize target changes under us */
1210 if (CMM_LOAD_SHARED(ht
->t
.resize_target
) > (1UL << (i
- 1)))
1213 cmm_smp_wmb(); /* populate data before RCU size */
1214 CMM_STORE_SHARED(ht
->t
.size
, 1UL << (i
- 1));
1217 * We need to wait for all add operations to reach Q.S. (and
1218 * thus use the new table for lookups) before we can start
1219 * releasing the old dummy nodes. Otherwise their lookup will
1220 * return a logically removed node as insert position.
1222 ht
->cds_lfht_synchronize_rcu();
1225 * Set "removed" flag in dummy nodes about to be removed.
1226 * Unlink all now-logically-removed dummy node pointers.
1227 * Concurrent add/remove operation are helping us doing
1230 remove_table(ht
, i
, len
);
1232 ht
->cds_lfht_call_rcu(&ht
->t
.tbl
[i
]->head
, cds_lfht_free_level
);
1234 dbg_printf("fini new size: %lu\n", 1UL << i
);
1235 if (CMM_LOAD_SHARED(ht
->in_progress_destroy
))
1240 struct cds_lfht
*_cds_lfht_new(cds_lfht_hash_fct hash_fct
,
1241 cds_lfht_compare_fct compare_fct
,
1242 unsigned long hash_seed
,
1243 unsigned long init_size
,
1245 void (*cds_lfht_call_rcu
)(struct rcu_head
*head
,
1246 void (*func
)(struct rcu_head
*head
)),
1247 void (*cds_lfht_synchronize_rcu
)(void),
1248 void (*cds_lfht_rcu_read_lock
)(void),
1249 void (*cds_lfht_rcu_read_unlock
)(void),
1250 void (*cds_lfht_rcu_thread_offline
)(void),
1251 void (*cds_lfht_rcu_thread_online
)(void),
1252 void (*cds_lfht_rcu_register_thread
)(void),
1253 void (*cds_lfht_rcu_unregister_thread
)(void),
1254 pthread_attr_t
*attr
)
1256 struct cds_lfht
*ht
;
1257 unsigned long order
;
1259 /* init_size must be power of two */
1260 if (init_size
&& (init_size
& (init_size
- 1)))
1262 ht
= calloc(1, sizeof(struct cds_lfht
));
1264 ht
->hash_fct
= hash_fct
;
1265 ht
->compare_fct
= compare_fct
;
1266 ht
->hash_seed
= hash_seed
;
1267 ht
->cds_lfht_call_rcu
= cds_lfht_call_rcu
;
1268 ht
->cds_lfht_synchronize_rcu
= cds_lfht_synchronize_rcu
;
1269 ht
->cds_lfht_rcu_read_lock
= cds_lfht_rcu_read_lock
;
1270 ht
->cds_lfht_rcu_read_unlock
= cds_lfht_rcu_read_unlock
;
1271 ht
->cds_lfht_rcu_thread_offline
= cds_lfht_rcu_thread_offline
;
1272 ht
->cds_lfht_rcu_thread_online
= cds_lfht_rcu_thread_online
;
1273 ht
->cds_lfht_rcu_register_thread
= cds_lfht_rcu_register_thread
;
1274 ht
->cds_lfht_rcu_unregister_thread
= cds_lfht_rcu_unregister_thread
;
1275 ht
->resize_attr
= attr
;
1276 ht
->percpu_count
= alloc_per_cpu_items_count();
1277 /* this mutex should not nest in read-side C.S. */
1278 pthread_mutex_init(&ht
->resize_mutex
, NULL
);
1279 order
= get_count_order_ulong(max(init_size
, MIN_TABLE_SIZE
)) + 1;
1281 ht
->cds_lfht_rcu_thread_offline();
1282 pthread_mutex_lock(&ht
->resize_mutex
);
1283 ht
->t
.resize_target
= 1UL << (order
- 1);
1284 init_table(ht
, 0, order
);
1285 pthread_mutex_unlock(&ht
->resize_mutex
);
1286 ht
->cds_lfht_rcu_thread_online();
1290 void cds_lfht_lookup(struct cds_lfht
*ht
, void *key
, size_t key_len
,
1291 struct cds_lfht_iter
*iter
)
1293 struct cds_lfht_node
*node
, *next
, *dummy_node
;
1294 struct _cds_lfht_node
*lookup
;
1295 unsigned long hash
, reverse_hash
, index
, order
, size
;
1297 hash
= ht
->hash_fct(key
, key_len
, ht
->hash_seed
);
1298 reverse_hash
= bit_reverse_ulong(hash
);
1300 size
= rcu_dereference(ht
->t
.size
);
1301 index
= hash
& (size
- 1);
1302 order
= get_count_order_ulong(index
+ 1);
1303 lookup
= &ht
->t
.tbl
[order
]->nodes
[index
& (!order
? 0 : ((1UL << (order
- 1))) - 1)];
1304 dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
1305 hash
, index
, order
, index
& (!order
? 0 : ((1UL << (order
- 1)) - 1)));
1306 dummy_node
= (struct cds_lfht_node
*) lookup
;
1307 /* We can always skip the dummy node initially */
1308 node
= rcu_dereference(dummy_node
->p
.next
);
1309 node
= clear_flag(node
);
1311 if (unlikely(is_end(node
))) {
1315 if (unlikely(node
->p
.reverse_hash
> reverse_hash
)) {
1319 next
= rcu_dereference(node
->p
.next
);
1320 if (likely(!is_removed(next
))
1322 && likely(!ht
->compare_fct(node
->key
, node
->key_len
, key
, key_len
))) {
1325 node
= clear_flag(next
);
1327 assert(!node
|| !is_dummy(rcu_dereference(node
->p
.next
)));
1332 void cds_lfht_next(struct cds_lfht
*ht
, struct cds_lfht_iter
*iter
)
1334 struct cds_lfht_node
*node
, *next
;
1335 unsigned long reverse_hash
;
1340 reverse_hash
= node
->p
.reverse_hash
;
1342 key_len
= node
->key_len
;
1344 node
= clear_flag(next
);
1347 if (unlikely(is_end(node
))) {
1351 if (unlikely(node
->p
.reverse_hash
> reverse_hash
)) {
1355 next
= rcu_dereference(node
->p
.next
);
1356 if (likely(!is_removed(next
))
1358 && likely(!ht
->compare_fct(node
->key
, node
->key_len
, key
, key_len
))) {
1361 node
= clear_flag(next
);
1363 assert(!node
|| !is_dummy(rcu_dereference(node
->p
.next
)));
1368 void cds_lfht_add(struct cds_lfht
*ht
, struct cds_lfht_node
*node
)
1370 unsigned long hash
, size
;
1372 hash
= ht
->hash_fct(node
->key
, node
->key_len
, ht
->hash_seed
);
1373 node
->p
.reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1375 size
= rcu_dereference(ht
->t
.size
);
1376 (void) _cds_lfht_add(ht
, size
, node
, ADD_DEFAULT
, 0);
1377 ht_count_add(ht
, size
);
1380 struct cds_lfht_node
*cds_lfht_add_unique(struct cds_lfht
*ht
,
1381 struct cds_lfht_node
*node
)
1383 unsigned long hash
, size
;
1384 struct cds_lfht_node
*ret
;
1386 hash
= ht
->hash_fct(node
->key
, node
->key_len
, ht
->hash_seed
);
1387 node
->p
.reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1389 size
= rcu_dereference(ht
->t
.size
);
1390 ret
= _cds_lfht_add(ht
, size
, node
, ADD_UNIQUE
, 0);
1392 ht_count_add(ht
, size
);
1396 struct cds_lfht_node
*cds_lfht_replace(struct cds_lfht
*ht
,
1397 struct cds_lfht_node
*node
)
1399 unsigned long hash
, size
;
1400 struct cds_lfht_node
*ret
;
1402 hash
= ht
->hash_fct(node
->key
, node
->key_len
, ht
->hash_seed
);
1403 node
->p
.reverse_hash
= bit_reverse_ulong((unsigned long) hash
);
1405 size
= rcu_dereference(ht
->t
.size
);
1406 ret
= _cds_lfht_add(ht
, size
, node
, ADD_REPLACE
, 0);
1408 ht_count_add(ht
, size
);
1412 int cds_lfht_del(struct cds_lfht
*ht
, struct cds_lfht_node
*node
)
1417 size
= rcu_dereference(ht
->t
.size
);
1418 ret
= _cds_lfht_del(ht
, size
, node
, 0, 1);
1420 ht_count_del(ht
, size
);
1425 int cds_lfht_delete_dummy(struct cds_lfht
*ht
)
1427 struct cds_lfht_node
*node
;
1428 struct _cds_lfht_node
*lookup
;
1429 unsigned long order
, i
, size
;
1431 /* Check that the table is empty */
1432 lookup
= &ht
->t
.tbl
[0]->nodes
[0];
1433 node
= (struct cds_lfht_node
*) lookup
;
1435 node
= clear_flag(node
)->p
.next
;
1436 if (!is_dummy(node
))
1438 assert(!is_removed(node
));
1439 assert(!is_gc(node
));
1440 } while (!is_end(node
));
1442 * size accessed without rcu_dereference because hash table is
1446 /* Internal sanity check: all nodes left should be dummy */
1447 for (order
= 0; order
< get_count_order_ulong(size
) + 1; order
++) {
1450 len
= !order
? 1 : 1UL << (order
- 1);
1451 for (i
= 0; i
< len
; i
++) {
1452 dbg_printf("delete order %lu i %lu hash %lu\n",
1454 bit_reverse_ulong(ht
->t
.tbl
[order
]->nodes
[i
].reverse_hash
));
1455 assert(is_dummy(ht
->t
.tbl
[order
]->nodes
[i
].next
));
1457 poison_free(ht
->t
.tbl
[order
]);
1463 * Should only be called when no more concurrent readers nor writers can
1464 * possibly access the table.
1466 int cds_lfht_destroy(struct cds_lfht
*ht
, pthread_attr_t
**attr
)
1470 /* Wait for in-flight resize operations to complete */
1471 CMM_STORE_SHARED(ht
->in_progress_destroy
, 1);
1472 while (uatomic_read(&ht
->in_progress_resize
))
1473 poll(NULL
, 0, 100); /* wait for 100ms */
1474 ret
= cds_lfht_delete_dummy(ht
);
1477 free_per_cpu_items_count(ht
->percpu_count
);
1479 *attr
= ht
->resize_attr
;
1484 void cds_lfht_count_nodes(struct cds_lfht
*ht
,
1485 unsigned long *count
,
1486 unsigned long *removed
)
1488 struct cds_lfht_node
*node
, *next
;
1489 struct _cds_lfht_node
*lookup
;
1490 unsigned long nr_dummy
= 0;
1495 /* Count non-dummy nodes in the table */
1496 lookup
= &ht
->t
.tbl
[0]->nodes
[0];
1497 node
= (struct cds_lfht_node
*) lookup
;
1499 next
= rcu_dereference(node
->p
.next
);
1500 if (is_removed(next
) || is_gc(next
)) {
1501 assert(!is_dummy(next
));
1503 } else if (!is_dummy(next
))
1507 node
= clear_flag(next
);
1508 } while (!is_end(node
));
1509 dbg_printf("number of dummy nodes: %lu\n", nr_dummy
);
1512 /* called with resize mutex held */
1514 void _do_cds_lfht_grow(struct cds_lfht
*ht
,
1515 unsigned long old_size
, unsigned long new_size
)
1517 unsigned long old_order
, new_order
;
1519 old_order
= get_count_order_ulong(old_size
) + 1;
1520 new_order
= get_count_order_ulong(new_size
) + 1;
1521 printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1522 old_size
, old_order
, new_size
, new_order
);
1523 assert(new_size
> old_size
);
1524 init_table(ht
, old_order
, new_order
- old_order
);
1527 /* called with resize mutex held */
1529 void _do_cds_lfht_shrink(struct cds_lfht
*ht
,
1530 unsigned long old_size
, unsigned long new_size
)
1532 unsigned long old_order
, new_order
;
1534 new_size
= max(new_size
, MIN_TABLE_SIZE
);
1535 old_order
= get_count_order_ulong(old_size
) + 1;
1536 new_order
= get_count_order_ulong(new_size
) + 1;
1537 printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
1538 old_size
, old_order
, new_size
, new_order
);
1539 assert(new_size
< old_size
);
1541 /* Remove and unlink all dummy nodes to remove. */
1542 fini_table(ht
, new_order
, old_order
- new_order
);
1546 /* called with resize mutex held */
1548 void _do_cds_lfht_resize(struct cds_lfht
*ht
)
1550 unsigned long new_size
, old_size
;
1553 * Resize table, re-do if the target size has changed under us.
1556 ht
->t
.resize_initiated
= 1;
1557 old_size
= ht
->t
.size
;
1558 new_size
= CMM_LOAD_SHARED(ht
->t
.resize_target
);
1559 if (old_size
< new_size
)
1560 _do_cds_lfht_grow(ht
, old_size
, new_size
);
1561 else if (old_size
> new_size
)
1562 _do_cds_lfht_shrink(ht
, old_size
, new_size
);
1563 ht
->t
.resize_initiated
= 0;
1564 /* write resize_initiated before read resize_target */
1566 } while (ht
->t
.size
!= CMM_LOAD_SHARED(ht
->t
.resize_target
));
1570 unsigned long resize_target_update(struct cds_lfht
*ht
, unsigned long size
,
1573 return _uatomic_max(&ht
->t
.resize_target
,
1574 size
<< growth_order
);
1578 void resize_target_update_count(struct cds_lfht
*ht
,
1579 unsigned long count
)
1581 count
= max(count
, MIN_TABLE_SIZE
);
1582 uatomic_set(&ht
->t
.resize_target
, count
);
1585 void cds_lfht_resize(struct cds_lfht
*ht
, unsigned long new_size
)
1587 resize_target_update_count(ht
, new_size
);
1588 CMM_STORE_SHARED(ht
->t
.resize_initiated
, 1);
1589 ht
->cds_lfht_rcu_thread_offline();
1590 pthread_mutex_lock(&ht
->resize_mutex
);
1591 _do_cds_lfht_resize(ht
);
1592 pthread_mutex_unlock(&ht
->resize_mutex
);
1593 ht
->cds_lfht_rcu_thread_online();
1597 void do_resize_cb(struct rcu_head
*head
)
1599 struct rcu_resize_work
*work
=
1600 caa_container_of(head
, struct rcu_resize_work
, head
);
1601 struct cds_lfht
*ht
= work
->ht
;
1603 ht
->cds_lfht_rcu_thread_offline();
1604 pthread_mutex_lock(&ht
->resize_mutex
);
1605 _do_cds_lfht_resize(ht
);
1606 pthread_mutex_unlock(&ht
->resize_mutex
);
1607 ht
->cds_lfht_rcu_thread_online();
1609 cmm_smp_mb(); /* finish resize before decrement */
1610 uatomic_dec(&ht
->in_progress_resize
);
1614 void cds_lfht_resize_lazy(struct cds_lfht
*ht
, unsigned long size
, int growth
)
1616 struct rcu_resize_work
*work
;
1617 unsigned long target_size
;
1619 target_size
= resize_target_update(ht
, size
, growth
);
1620 /* Store resize_target before read resize_initiated */
1622 if (!CMM_LOAD_SHARED(ht
->t
.resize_initiated
) && size
< target_size
) {
1623 uatomic_inc(&ht
->in_progress_resize
);
1624 cmm_smp_mb(); /* increment resize count before calling it */
1625 work
= malloc(sizeof(*work
));
1627 ht
->cds_lfht_call_rcu(&work
->head
, do_resize_cb
);
1628 CMM_STORE_SHARED(ht
->t
.resize_initiated
, 1);
1632 #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
1635 void cds_lfht_resize_lazy_count(struct cds_lfht
*ht
, unsigned long size
,
1636 unsigned long count
)
1638 struct rcu_resize_work
*work
;
1640 if (!(ht
->flags
& CDS_LFHT_AUTO_RESIZE
))
1642 resize_target_update_count(ht
, count
);
1643 /* Store resize_target before read resize_initiated */
1645 if (!CMM_LOAD_SHARED(ht
->t
.resize_initiated
)) {
1646 uatomic_inc(&ht
->in_progress_resize
);
1647 cmm_smp_mb(); /* increment resize count before calling it */
1648 work
= malloc(sizeof(*work
));
1650 ht
->cds_lfht_call_rcu(&work
->head
, do_resize_cb
);
1651 CMM_STORE_SHARED(ht
->t
.resize_initiated
, 1);