Commit | Line | Data |
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2ed95849 MD |
1 | |
2 | #define _LGPL_SOURCE | |
3 | #include <stdlib.h> | |
4 | #include <urcu.h> | |
5 | #include <arch.h> | |
6 | #include <arch_atomic.h> | |
7 | #include <assert.h> | |
8 | #include <compiler.h> | |
9 | #include <urcu-defer.h> | |
10 | #include <errno.h> | |
ab7d5fc6 | 11 | #include <urcu-ht.h> |
2ed95849 MD |
12 | |
13 | struct rcu_ht_node; | |
14 | ||
15 | struct rcu_ht_node { | |
16 | struct rcu_ht_node *next; | |
17 | void *key; | |
18 | void *data; | |
19 | }; | |
20 | ||
21 | struct rcu_ht { | |
22 | struct rcu_ht_node *tbl[HASH_SIZE]; | |
23 | ht_hash_fct hash_fct; | |
24 | void (*free_fct)(void *data); /* fct to free data */ | |
25 | }; | |
26 | ||
2ed95849 MD |
27 | struct rcu_ht *ht_new(ht_hash_fct hash_fct, void (*free_fct)(void *data)) |
28 | { | |
29 | struct rcu_ht *ht; | |
30 | ||
31 | ht = calloc(1, sizeof(struct rcu_ht)); | |
32 | ht->hash_fct = hash_fct; | |
33 | ht->free_fct = free_fct; | |
ab7d5fc6 | 34 | return ht; |
2ed95849 MD |
35 | } |
36 | ||
37 | /* delete all elements */ | |
38 | void ht_delete_all(struct rcu_ht *ht) | |
39 | { | |
40 | unsigned long i; | |
41 | struct rcu_ht_node **prev, *node; | |
42 | ||
43 | for (i = 0; i < HASH_SIZE; i++) { | |
44 | rcu_read_lock(); | |
45 | ||
46 | prev = &ht->tbl[i]; | |
47 | node = rcu_dereference(*prev); | |
48 | /* | |
49 | * Cut the head, therefore whole bucket will be unused | |
50 | * after GP. (except for concurrent additions) | |
51 | */ | |
52 | rcu_assign_pointer(prev, NULL); | |
53 | for (;;) { | |
54 | if (likely(!node)) { | |
55 | break; | |
56 | } | |
57 | prev = &node->next; | |
1a3d00b3 MD |
58 | /* |
59 | * FIXME: calling call_rcu within a read-side C.S. is a | |
60 | * bug, because it may call synchronize_rcu() if the | |
61 | * callback queue is full. | |
62 | */ | |
2ed95849 MD |
63 | if (node->data) |
64 | call_rcu(ht->free_fct, node->data); | |
65 | call_rcu(free, node); | |
66 | node = rcu_dereference(*prev); | |
67 | } | |
68 | rcu_read_unlock(); | |
69 | } | |
70 | } | |
71 | ||
72 | /* | |
73 | * Should only be called when no more concurrent readers nor writers can | |
74 | * possibly access the table. | |
75 | */ | |
ab7d5fc6 | 76 | void ht_destroy(struct rcu_ht *ht) |
2ed95849 MD |
77 | { |
78 | ht_delete_all(ht); | |
79 | free(ht); | |
80 | } | |
81 | ||
82 | void *ht_lookup(struct rcu_ht *ht, void *key) | |
83 | { | |
84 | unsigned long hash; | |
85 | struct rcu_ht_node *node; | |
86 | void *ret; | |
87 | ||
88 | hash = ht->hash_fct(key); | |
89 | ||
90 | rcu_read_lock(); | |
91 | node = rcu_dereference(ht->tbl[hash]); | |
92 | for (;;) { | |
93 | if (likely(!node)) { | |
94 | ret = NULL; | |
95 | break; | |
96 | } | |
97 | if (node->key == key) { | |
98 | ret = node->data; | |
99 | break; | |
100 | } | |
101 | node = rcu_dereference(node->next); | |
102 | } | |
103 | rcu_read_unlock(); | |
ab7d5fc6 MD |
104 | |
105 | return ret; | |
2ed95849 MD |
106 | } |
107 | ||
108 | /* | |
109 | * Will re-try until either: | |
110 | * - The key is already there (-EEXIST) | |
111 | * - We successfully add the key at the head of a table bucket. | |
112 | */ | |
113 | int ht_add(struct rcu_ht *ht, void *key, void *data) | |
114 | { | |
115 | struct rcu_ht_node *node, *old_head, *new_head; | |
116 | unsigned long hash; | |
117 | int ret = 0; | |
118 | ||
119 | new_head = calloc(1, sizeof(struct rcu_ht_node)); | |
120 | new_head->key = key; | |
121 | new_head->data = data; | |
122 | hash = ht->hash_fct(key); | |
123 | ||
124 | /* here comes the fun and tricky part. | |
125 | * Add at the beginning with a cmpxchg. | |
126 | * Hold a read lock between the moment the first element is read | |
127 | * and the nodes traversal (to find duplicates). This ensures | |
128 | * the head pointer has not been reclaimed when cmpxchg is done. | |
129 | * Always adding at the head ensures that we would have to | |
130 | * re-try if a new item has been added concurrently. So we ensure that | |
131 | * we never add duplicates. */ | |
132 | retry: | |
133 | rcu_read_lock(); | |
134 | ||
135 | old_head = node = rcu_dereference(ht->tbl[hash]); | |
136 | for (;;) { | |
137 | if (likely(!node)) { | |
138 | break; | |
139 | } | |
140 | if (node->key == key) { | |
141 | ret = -EEXIST; | |
142 | goto end; | |
143 | } | |
144 | node = rcu_dereference(node->next); | |
145 | } | |
146 | if (rcu_cmpxchg_pointer(&ht->tbl[hash], old_head, new_head) != old_head) | |
147 | goto restart; | |
148 | end: | |
149 | rcu_read_unlock(); | |
150 | ||
151 | return ret; | |
152 | ||
153 | /* restart loop, release and re-take the read lock to be kind to GP */ | |
154 | restart: | |
155 | rcu_read_unlock(); | |
156 | goto retry; | |
157 | } | |
158 | ||
159 | /* | |
160 | * Restart until we successfully remove the entry, or no entry is left | |
161 | * ((void *)(unsigned long)-ENOENT). | |
162 | */ | |
ab7d5fc6 | 163 | void *ht_steal(struct rcu_ht *ht, void *key) |
2ed95849 MD |
164 | { |
165 | struct rcu_ht_node **prev, *node; | |
166 | unsigned long hash; | |
ab7d5fc6 | 167 | void *data; |
2ed95849 MD |
168 | |
169 | hash = ht->hash_fct(key); | |
170 | ||
171 | retry: | |
172 | rcu_read_lock(); | |
173 | ||
174 | prev = &ht->tbl[hash]; | |
175 | node = rcu_dereference(*prev); | |
176 | for (;;) { | |
177 | if (likely(!node)) { | |
ab7d5fc6 | 178 | data = (void *)(unsigned long)-ENOENT; |
2ed95849 MD |
179 | goto end; |
180 | } | |
181 | if (node->key == key) { | |
182 | break; | |
183 | } | |
184 | prev = &node->next; | |
185 | node = rcu_dereference(*prev); | |
186 | } | |
187 | /* Found it ! pointer to object is in "prev" */ | |
188 | if (rcu_cmpxchg_pointer(prev, node, node->next) != node) | |
189 | goto restart; | |
190 | end: | |
191 | rcu_read_unlock(); | |
192 | ||
ab7d5fc6 MD |
193 | data = node->data; |
194 | call_rcu(free, node); | |
195 | ||
196 | return data; | |
2ed95849 MD |
197 | |
198 | /* restart loop, release and re-take the read lock to be kind to GP */ | |
199 | restart: | |
200 | rcu_read_unlock(); | |
201 | goto retry; | |
202 | } | |
203 | ||
204 | int ht_delete(struct rcu_ht *ht, void *key) | |
205 | { | |
ab7d5fc6 | 206 | void *data; |
2ed95849 | 207 | |
ab7d5fc6 MD |
208 | data = ht_steal(ht, key); |
209 | if (data) { | |
210 | if (ht->free_fct && data) | |
211 | call_rcu(ht->free_fct, data); | |
2ed95849 MD |
212 | return 0; |
213 | } else { | |
214 | return -ENOENT; | |
215 | } | |
216 | } | |
ab7d5fc6 MD |
217 | |
218 | unsigned long stupid_hash(void *key) | |
219 | { | |
220 | return (unsigned long)key % HASH_SIZE; | |
221 | } |