14f39e1f8ba32534dd79bee243645205ba46ab78
1 // SPDX-FileCopyrightText: 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
3 // SPDX-License-Identifier: MIT
6 * This example shows how to iterate on duplicate keys within a RCU
7 * lock-free hash table. This hash table requires using a RCU scheme.
14 #include <urcu/urcu-memb.h> /* RCU flavor */
15 #include <urcu/rculfhash.h> /* RCU Lock-free hash table */
16 #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */
17 #include "jhash.h" /* Example hash function */
20 * Nodes populated into the hash table.
23 int value
; /* Node content */
24 int seqnum
; /* Our node sequence number */
25 struct cds_lfht_node node
; /* Chaining in hash table */
29 int match(struct cds_lfht_node
*ht_node
, const void *_key
)
32 caa_container_of(ht_node
, struct mynode
, node
);
33 const int *key
= _key
;
35 return *key
== node
->value
;
40 int values
[] = { -5, 42, 42, 36, 24, }; /* 42 is duplicated */
41 int lookup_values
[] = { 42, 200, 36, };
42 struct cds_lfht
*ht
; /* Hash table */
44 int ret
= 0, seqnum
= 0;
46 struct cds_lfht_iter iter
; /* For iteration on hash table */
50 * Each thread need using RCU read-side need to be explicitly
53 urcu_memb_register_thread();
55 /* Use time as seed for hash table hashing. */
56 seed
= (uint32_t) time(NULL
);
59 * Allocate hash table.
61 ht
= cds_lfht_new_flavor(1, 1, 0,
62 CDS_LFHT_AUTO_RESIZE
| CDS_LFHT_ACCOUNTING
,
63 &urcu_memb_flavor
, NULL
);
65 printf("Error allocating hash table\n");
71 * Add nodes to hash table.
73 for (i
= 0; i
< CAA_ARRAY_SIZE(values
); i
++) {
77 node
= malloc(sizeof(*node
));
83 cds_lfht_node_init(&node
->node
);
86 node
->seqnum
= seqnum
++;
87 hash
= jhash(&value
, sizeof(value
), seed
);
90 * cds_lfht_add() needs to be called from RCU read-side
93 urcu_memb_read_lock();
94 cds_lfht_add(ht
, hash
, &node
->node
);
95 printf("Add (key: %d, seqnum: %d)\n",
96 node
->value
, node
->seqnum
);
97 urcu_memb_read_unlock();
101 * Iterate over each hash table node. Those will appear in
102 * random order, depending on the hash seed. Iteration needs to
103 * be performed within RCU read-side critical section.
105 printf("hash table content (random order):");
106 urcu_memb_read_lock();
107 cds_lfht_for_each_entry(ht
, &iter
, node
, node
) {
108 printf(" (key: %d, seqnum: %d)",
109 node
->value
, node
->seqnum
);
111 urcu_memb_read_unlock();
115 * Lookup queries. Note that which node (seqnum) within
116 * duplicates will be found by lookup is random.
118 printf("Lookups, with iteration on duplicates:\n");
119 for (i
= 0; i
< CAA_ARRAY_SIZE(lookup_values
); i
++) {
120 int value
= lookup_values
[i
];
121 unsigned long hash
= jhash(&value
, sizeof(value
), seed
);
123 printf("lookup key: %d\n", value
);
124 urcu_memb_read_lock();
125 cds_lfht_for_each_entry_duplicate(ht
, hash
, match
,
126 &value
, &iter
, node
, node
) {
127 printf(" (key %d, seqnum %d) found\n",
128 node
->value
, node
->seqnum
);
130 urcu_memb_read_unlock();
134 urcu_memb_unregister_thread();
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