Commit | Line | Data |
---|---|---|
2ed95849 | 1 | |
5e28c532 MD |
2 | /* |
3 | * TODO: keys are currently assumed <= sizeof(void *). Key target never freed. | |
4 | */ | |
5 | ||
2ed95849 MD |
6 | #define _LGPL_SOURCE |
7 | #include <stdlib.h> | |
e0ba718a MD |
8 | #include <errno.h> |
9 | #include <assert.h> | |
10 | #include <stdio.h> | |
11 | ||
2ed95849 | 12 | #include <urcu.h> |
e0ba718a | 13 | #include <urcu-defer.h> |
2ed95849 MD |
14 | #include <arch.h> |
15 | #include <arch_atomic.h> | |
2ed95849 | 16 | #include <compiler.h> |
674f7a69 | 17 | #include <urcu/jhash.h> |
5e28c532 | 18 | #include <stdio.h> |
464a1ec9 | 19 | #include <pthread.h> |
e0ba718a | 20 | #include <urcu-ht.h> |
2ed95849 | 21 | |
44395fb7 MD |
22 | /* |
23 | * Maximum number of hash table buckets: 256M on 64-bit. | |
24 | * Should take about 512MB max if we assume 1 node per 4 buckets. | |
25 | */ | |
26 | #define MAX_HT_BUCKETS ((256 << 10) / sizeof(void *)) | |
27 | ||
3df2df75 MD |
28 | /* node flags */ |
29 | #define NODE_STOLEN (1 << 0) | |
2ed95849 MD |
30 | |
31 | struct rcu_ht_node; | |
32 | ||
33 | struct rcu_ht_node { | |
34 | struct rcu_ht_node *next; | |
35 | void *key; | |
36 | void *data; | |
3df2df75 | 37 | unsigned int flags; |
2ed95849 MD |
38 | }; |
39 | ||
40 | struct rcu_ht { | |
674f7a69 | 41 | struct rcu_ht_node **tbl; |
2ed95849 MD |
42 | ht_hash_fct hash_fct; |
43 | void (*free_fct)(void *data); /* fct to free data */ | |
464a1ec9 | 44 | unsigned long size; |
5e28c532 MD |
45 | uint32_t keylen; |
46 | uint32_t hashseed; | |
464a1ec9 MD |
47 | pthread_mutex_t resize_mutex; /* resize mutex: add/del mutex */ |
48 | int resize_ongoing; /* fast-path resize check */ | |
2ed95849 MD |
49 | }; |
50 | ||
674f7a69 | 51 | struct rcu_ht *ht_new(ht_hash_fct hash_fct, void (*free_fct)(void *data), |
5e28c532 MD |
52 | unsigned long init_size, uint32_t keylen, |
53 | uint32_t hashseed) | |
2ed95849 MD |
54 | { |
55 | struct rcu_ht *ht; | |
56 | ||
57 | ht = calloc(1, sizeof(struct rcu_ht)); | |
58 | ht->hash_fct = hash_fct; | |
59 | ht->free_fct = free_fct; | |
44395fb7 | 60 | ht->size = init_size; /* shared */ |
5e28c532 MD |
61 | ht->keylen = keylen; |
62 | ht->hashseed = hashseed; | |
464a1ec9 MD |
63 | /* this mutex should not nest in read-side C.S. */ |
64 | pthread_mutex_init(&ht->resize_mutex, NULL); | |
44395fb7 | 65 | ht->resize_ongoing = 0; /* shared */ |
674f7a69 | 66 | ht->tbl = calloc(init_size, sizeof(struct rcu_ht_node *)); |
ab7d5fc6 | 67 | return ht; |
2ed95849 MD |
68 | } |
69 | ||
2ed95849 MD |
70 | void *ht_lookup(struct rcu_ht *ht, void *key) |
71 | { | |
72 | unsigned long hash; | |
73 | struct rcu_ht_node *node; | |
74 | void *ret; | |
75 | ||
464a1ec9 MD |
76 | hash = ht->hash_fct(key, ht->keylen, ht->hashseed) % ht->size; |
77 | smp_read_barrier_depends(); /* read size before links */ | |
2ed95849 MD |
78 | |
79 | rcu_read_lock(); | |
5e28c532 | 80 | node = rcu_dereference(ht->tbl[hash]); |
2ed95849 MD |
81 | for (;;) { |
82 | if (likely(!node)) { | |
83 | ret = NULL; | |
84 | break; | |
85 | } | |
86 | if (node->key == key) { | |
87 | ret = node->data; | |
88 | break; | |
89 | } | |
90 | node = rcu_dereference(node->next); | |
91 | } | |
92 | rcu_read_unlock(); | |
ab7d5fc6 MD |
93 | |
94 | return ret; | |
2ed95849 MD |
95 | } |
96 | ||
97 | /* | |
98 | * Will re-try until either: | |
99 | * - The key is already there (-EEXIST) | |
100 | * - We successfully add the key at the head of a table bucket. | |
101 | */ | |
102 | int ht_add(struct rcu_ht *ht, void *key, void *data) | |
103 | { | |
104 | struct rcu_ht_node *node, *old_head, *new_head; | |
105 | unsigned long hash; | |
106 | int ret = 0; | |
107 | ||
108 | new_head = calloc(1, sizeof(struct rcu_ht_node)); | |
109 | new_head->key = key; | |
110 | new_head->data = data; | |
3df2df75 | 111 | new_head->flags = 0; |
2ed95849 MD |
112 | /* here comes the fun and tricky part. |
113 | * Add at the beginning with a cmpxchg. | |
114 | * Hold a read lock between the moment the first element is read | |
115 | * and the nodes traversal (to find duplicates). This ensures | |
116 | * the head pointer has not been reclaimed when cmpxchg is done. | |
117 | * Always adding at the head ensures that we would have to | |
118 | * re-try if a new item has been added concurrently. So we ensure that | |
119 | * we never add duplicates. */ | |
120 | retry: | |
121 | rcu_read_lock(); | |
122 | ||
44395fb7 | 123 | if (unlikely(LOAD_SHARED(ht->resize_ongoing))) { |
464a1ec9 MD |
124 | rcu_read_unlock(); |
125 | /* | |
126 | * Wait for resize to complete before continuing. | |
127 | */ | |
128 | ret = pthread_mutex_lock(&ht->resize_mutex); | |
129 | assert(!ret); | |
130 | ret = pthread_mutex_unlock(&ht->resize_mutex); | |
131 | assert(!ret); | |
132 | goto retry; | |
133 | } | |
134 | ||
44395fb7 MD |
135 | hash = ht->hash_fct(key, ht->keylen, ht->hashseed) |
136 | % LOAD_SHARED(ht->size); | |
5e28c532 MD |
137 | |
138 | old_head = node = rcu_dereference(ht->tbl[hash]); | |
2ed95849 MD |
139 | for (;;) { |
140 | if (likely(!node)) { | |
141 | break; | |
142 | } | |
143 | if (node->key == key) { | |
144 | ret = -EEXIST; | |
145 | goto end; | |
146 | } | |
147 | node = rcu_dereference(node->next); | |
148 | } | |
5e28c532 MD |
149 | new_head->next = old_head; |
150 | if (rcu_cmpxchg_pointer(&ht->tbl[hash], old_head, new_head) != old_head) | |
2ed95849 MD |
151 | goto restart; |
152 | end: | |
153 | rcu_read_unlock(); | |
2ed95849 MD |
154 | return ret; |
155 | ||
156 | /* restart loop, release and re-take the read lock to be kind to GP */ | |
157 | restart: | |
158 | rcu_read_unlock(); | |
159 | goto retry; | |
160 | } | |
161 | ||
162 | /* | |
163 | * Restart until we successfully remove the entry, or no entry is left | |
164 | * ((void *)(unsigned long)-ENOENT). | |
e0ba718a MD |
165 | * Deal with concurrent stealers by doing an extra verification pass to check |
166 | * that no element in the list are still pointing to the element stolen. | |
167 | * This could happen if two concurrent steal for consecutive objects are | |
168 | * executed. A pointer to an object being stolen could be saved by the | |
169 | * concurrent stealer for the previous object. | |
170 | * Also, given that in this precise scenario, another stealer can also want to | |
171 | * delete the doubly-referenced object; use a "stolen" flag to let only one | |
172 | * stealer delete the object. | |
2ed95849 | 173 | */ |
ab7d5fc6 | 174 | void *ht_steal(struct rcu_ht *ht, void *key) |
2ed95849 | 175 | { |
2e6070d0 | 176 | struct rcu_ht_node **prev, *node, *del_node = NULL; |
2ed95849 | 177 | unsigned long hash; |
ab7d5fc6 | 178 | void *data; |
464a1ec9 | 179 | int ret; |
2ed95849 | 180 | |
2ed95849 MD |
181 | retry: |
182 | rcu_read_lock(); | |
183 | ||
44395fb7 | 184 | if (unlikely(LOAD_SHARED(ht->resize_ongoing))) { |
464a1ec9 MD |
185 | rcu_read_unlock(); |
186 | /* | |
187 | * Wait for resize to complete before continuing. | |
188 | */ | |
189 | ret = pthread_mutex_lock(&ht->resize_mutex); | |
190 | assert(!ret); | |
191 | ret = pthread_mutex_unlock(&ht->resize_mutex); | |
192 | assert(!ret); | |
193 | goto retry; | |
194 | } | |
195 | ||
44395fb7 MD |
196 | hash = ht->hash_fct(key, ht->keylen, ht->hashseed) |
197 | % LOAD_SHARED(ht->size); | |
5e28c532 MD |
198 | |
199 | prev = &ht->tbl[hash]; | |
2ed95849 MD |
200 | node = rcu_dereference(*prev); |
201 | for (;;) { | |
202 | if (likely(!node)) { | |
2e6070d0 MD |
203 | if (del_node) { |
204 | goto end; | |
205 | } else { | |
2e6070d0 MD |
206 | goto error; |
207 | } | |
2ed95849 MD |
208 | } |
209 | if (node->key == key) { | |
210 | break; | |
211 | } | |
212 | prev = &node->next; | |
213 | node = rcu_dereference(*prev); | |
214 | } | |
e0ba718a | 215 | |
85f6ba5f MD |
216 | if (!del_node) { |
217 | /* | |
218 | * Another concurrent thread stole it ? If so, let it deal with | |
3df2df75 MD |
219 | * this. Assume NODE_STOLEN is the only flag. If this changes, |
220 | * read flags before cmpxchg. | |
85f6ba5f | 221 | */ |
3df2df75 | 222 | if (cmpxchg(&node->flags, 0, NODE_STOLEN) != 0) |
85f6ba5f MD |
223 | goto error; |
224 | } | |
e0ba718a | 225 | |
2ed95849 | 226 | /* Found it ! pointer to object is in "prev" */ |
7ce4eb38 | 227 | if (rcu_cmpxchg_pointer(prev, node, node->next) == node) |
2e6070d0 MD |
228 | del_node = node; |
229 | goto restart; | |
5e28c532 | 230 | |
2e6070d0 MD |
231 | end: |
232 | /* | |
233 | * From that point, we own node. Note that there can still be concurrent | |
234 | * RCU readers using it. We can free it outside of read lock after a GP. | |
235 | */ | |
2ed95849 MD |
236 | rcu_read_unlock(); |
237 | ||
567d7550 MD |
238 | data = del_node->data; |
239 | call_rcu(free, del_node); | |
5e28c532 | 240 | return data; |
ab7d5fc6 | 241 | |
5e28c532 | 242 | error: |
e0ba718a | 243 | data = (void *)(unsigned long)-ENOENT; |
5e28c532 | 244 | rcu_read_unlock(); |
ab7d5fc6 | 245 | return data; |
2ed95849 MD |
246 | |
247 | /* restart loop, release and re-take the read lock to be kind to GP */ | |
248 | restart: | |
249 | rcu_read_unlock(); | |
250 | goto retry; | |
251 | } | |
252 | ||
253 | int ht_delete(struct rcu_ht *ht, void *key) | |
254 | { | |
ab7d5fc6 | 255 | void *data; |
2ed95849 | 256 | |
ab7d5fc6 | 257 | data = ht_steal(ht, key); |
5e28c532 MD |
258 | if (data && data != (void *)(unsigned long)-ENOENT) { |
259 | if (ht->free_fct) | |
ab7d5fc6 | 260 | call_rcu(ht->free_fct, data); |
2ed95849 MD |
261 | return 0; |
262 | } else { | |
263 | return -ENOENT; | |
264 | } | |
265 | } | |
ab7d5fc6 | 266 | |
674f7a69 | 267 | /* Delete all old elements. Allow concurrent writer accesses. */ |
5e28c532 | 268 | int ht_delete_all(struct rcu_ht *ht) |
674f7a69 MD |
269 | { |
270 | unsigned long i; | |
271 | struct rcu_ht_node **prev, *node, *inext; | |
5e28c532 | 272 | int cnt = 0; |
464a1ec9 MD |
273 | int ret; |
274 | ||
275 | /* | |
276 | * Mutual exclusion with resize operations, but leave add/steal execute | |
277 | * concurrently. This is OK because we operate only on the heads. | |
278 | */ | |
279 | ret = pthread_mutex_lock(&ht->resize_mutex); | |
280 | assert(!ret); | |
674f7a69 | 281 | |
464a1ec9 | 282 | for (i = 0; i < ht->size; i++) { |
674f7a69 | 283 | rcu_read_lock(); |
5e28c532 MD |
284 | prev = &ht->tbl[i]; |
285 | /* | |
286 | * Cut the head. After that, we own the first element. | |
287 | */ | |
288 | node = rcu_xchg_pointer(prev, NULL); | |
289 | if (!node) { | |
674f7a69 MD |
290 | rcu_read_unlock(); |
291 | continue; | |
292 | } | |
293 | /* | |
294 | * We manage a list shared with concurrent writers and readers. | |
295 | * Note that a concurrent add may or may not be deleted by us, | |
296 | * depending if it arrives before or after the head is cut. | |
297 | * "node" points to our first node. Remove first elements | |
298 | * iteratively. | |
299 | */ | |
300 | for (;;) { | |
5e28c532 | 301 | inext = NULL; |
674f7a69 | 302 | prev = &node->next; |
5e28c532 MD |
303 | if (prev) |
304 | inext = rcu_xchg_pointer(prev, NULL); | |
674f7a69 MD |
305 | /* |
306 | * "node" is the first element of the list we have cut. | |
307 | * We therefore own it, no concurrent writer may delete | |
308 | * it. There can only be concurrent lookups. Concurrent | |
309 | * add can only be done on a bucket head, but we've cut | |
310 | * it already. inext is also owned by us, because we | |
311 | * have exchanged it for "NULL". It will therefore be | |
312 | * safe to use it after a G.P. | |
313 | */ | |
314 | rcu_read_unlock(); | |
315 | if (node->data) | |
316 | call_rcu(ht->free_fct, node->data); | |
317 | call_rcu(free, node); | |
5e28c532 | 318 | cnt++; |
674f7a69 MD |
319 | if (likely(!inext)) |
320 | break; | |
321 | rcu_read_lock(); | |
322 | node = inext; | |
323 | } | |
324 | } | |
464a1ec9 MD |
325 | |
326 | ret = pthread_mutex_unlock(&ht->resize_mutex); | |
327 | assert(!ret); | |
5e28c532 | 328 | return cnt; |
674f7a69 MD |
329 | } |
330 | ||
331 | /* | |
332 | * Should only be called when no more concurrent readers nor writers can | |
333 | * possibly access the table. | |
334 | */ | |
5e28c532 | 335 | int ht_destroy(struct rcu_ht *ht) |
674f7a69 | 336 | { |
5e28c532 MD |
337 | int ret; |
338 | ||
339 | ret = ht_delete_all(ht); | |
674f7a69 MD |
340 | free(ht->tbl); |
341 | free(ht); | |
5e28c532 | 342 | return ret; |
674f7a69 MD |
343 | } |
344 | ||
464a1ec9 MD |
345 | static void ht_resize_grow(struct rcu_ht *ht) |
346 | { | |
347 | unsigned long i, new_size, old_size; | |
348 | struct rcu_ht_node **new_tbl, **old_tbl; | |
349 | struct rcu_ht_node *node, *new_node, *tmp; | |
350 | unsigned long hash; | |
351 | ||
352 | old_size = ht->size; | |
353 | ||
44395fb7 | 354 | if (old_size == MAX_HT_BUCKETS) |
464a1ec9 MD |
355 | return; |
356 | ||
44395fb7 | 357 | old_tbl = ht->tbl; |
464a1ec9 MD |
358 | new_size = old_size << 1; |
359 | new_tbl = calloc(new_size, sizeof(struct rcu_ht_node *)); | |
360 | ||
361 | for (i = 0; i < old_size; i++) { | |
362 | /* | |
363 | * Re-hash each entry, insert in new table. | |
364 | * It's important that a reader looking for a key _will_ find it | |
365 | * if it's in the table. | |
366 | * Copy each node. (just the node, not ->data) | |
367 | */ | |
44395fb7 | 368 | node = old_tbl[i]; |
464a1ec9 MD |
369 | while (node) { |
370 | hash = ht->hash_fct(node->key, ht->keylen, ht->hashseed) | |
371 | % new_size; | |
372 | new_node = malloc(sizeof(struct rcu_ht_node)); | |
373 | new_node->key = node->key; | |
374 | new_node->data = node->data; | |
44395fb7 MD |
375 | new_node->next = new_tbl[hash]; /* add to head */ |
376 | new_tbl[hash] = new_node; | |
464a1ec9 MD |
377 | node = node->next; |
378 | } | |
379 | } | |
380 | ||
464a1ec9 MD |
381 | ht->tbl = new_tbl; |
382 | smp_wmb(); /* write links and table before changing size */ | |
44395fb7 | 383 | STORE_SHARED(ht->size, new_size); |
464a1ec9 MD |
384 | |
385 | /* Ensure all concurrent lookups use new size and table */ | |
386 | synchronize_rcu(); | |
387 | ||
388 | for (i = 0; i < old_size; i++) { | |
389 | node = old_tbl[i]; | |
390 | while (node) { | |
391 | tmp = node->next; | |
392 | free(node); | |
393 | node = tmp; | |
394 | } | |
395 | } | |
396 | free(old_tbl); | |
397 | } | |
398 | ||
399 | static void ht_resize_shrink(struct rcu_ht *ht) | |
400 | { | |
401 | unsigned long i, new_size; | |
402 | struct rcu_ht_node **new_tbl; | |
403 | struct rcu_ht_node **prev, *node; | |
404 | ||
405 | if (ht->size == 1) | |
406 | return; | |
407 | ||
408 | new_size = ht->size >> 1; | |
409 | ||
410 | for (i = 0; i < new_size; i++) { | |
44395fb7 | 411 | /* Link end with first entry of i + new_size */ |
464a1ec9 MD |
412 | prev = &ht->tbl[i]; |
413 | node = *prev; | |
414 | while (node) { | |
415 | prev = &node->next; | |
416 | node = *prev; | |
417 | } | |
44395fb7 | 418 | *prev = ht->tbl[i + new_size]; |
464a1ec9 MD |
419 | } |
420 | smp_wmb(); /* write links before changing size */ | |
44395fb7 | 421 | STORE_SHARED(ht->size, new_size); |
464a1ec9 MD |
422 | |
423 | /* Ensure all concurrent lookups use new size */ | |
424 | synchronize_rcu(); | |
425 | ||
426 | new_tbl = realloc(ht->tbl, new_size * sizeof(struct rcu_ht_node *)); | |
427 | /* shrinking, pointers should not move */ | |
428 | assert(new_tbl == ht->tbl); | |
429 | } | |
430 | ||
431 | /* | |
432 | * growth: >0: *2, <0: /2 | |
433 | */ | |
434 | void ht_resize(struct rcu_ht *ht, int growth) | |
435 | { | |
436 | int ret; | |
437 | ||
438 | ret = pthread_mutex_lock(&ht->resize_mutex); | |
439 | assert(!ret); | |
44395fb7 | 440 | STORE_SHARED(ht->resize_ongoing, 1); |
464a1ec9 MD |
441 | synchronize_rcu(); |
442 | /* All add/remove are waiting on the mutex. */ | |
443 | if (growth > 0) | |
444 | ht_resize_grow(ht); | |
445 | else if (growth < 0) | |
446 | ht_resize_shrink(ht); | |
447 | smp_mb(); | |
44395fb7 | 448 | STORE_SHARED(ht->resize_ongoing, 0); |
464a1ec9 MD |
449 | ret = pthread_mutex_unlock(&ht->resize_mutex); |
450 | assert(!ret); | |
451 | } | |
452 | ||
5e28c532 MD |
453 | /* |
454 | * Expects keys <= than pointer size to be encoded in the pointer itself. | |
455 | */ | |
674f7a69 | 456 | uint32_t ht_jhash(void *key, uint32_t length, uint32_t initval) |
ab7d5fc6 | 457 | { |
5e28c532 MD |
458 | uint32_t ret; |
459 | void *vkey; | |
460 | ||
0eb566f4 | 461 | if (length <= sizeof(void *)) |
5e28c532 MD |
462 | vkey = &key; |
463 | else | |
464 | vkey = key; | |
465 | ret = jhash(vkey, length, initval); | |
466 | return ret; | |
ab7d5fc6 | 467 | } |