| 1 | /* |
| 2 | * rcuja/rcuja-range.c |
| 3 | * |
| 4 | * Userspace RCU library - RCU Judy Array Range Support |
| 5 | * |
| 6 | * Copyright 2012-2013 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 7 | * |
| 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. |
| 12 | * |
| 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. |
| 17 | * |
| 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 |
| 21 | */ |
| 22 | |
| 23 | #define _LGPL_SOURCE |
| 24 | #include <stdint.h> |
| 25 | #include <errno.h> |
| 26 | #include <limits.h> |
| 27 | #include <string.h> |
| 28 | #include <assert.h> |
| 29 | #include <pthread.h> |
| 30 | #include <urcu/rcuja.h> |
| 31 | #include <urcu/compiler.h> |
| 32 | #include <urcu/arch.h> |
| 33 | #include <urcu-pointer.h> |
| 34 | #include <urcu/uatomic.h> |
| 35 | #include <urcu/rcuja-range.h> |
| 36 | #include <urcu-flavor.h> |
| 37 | |
| 38 | #include "rcuja-internal.h" |
| 39 | |
| 40 | /* |
| 41 | * Discussion about order of lookup/lock vs allocated node deletion. |
| 42 | * |
| 43 | * - If node deletion returns before call to |
| 44 | * cds_ja_range_lookup(), the node will not be found by lookup. |
| 45 | * - If node deletion is called after cds_ja_range_lock() returns a |
| 46 | * non-NULL range, the deletion will wait until the lock is released |
| 47 | * before it takes place. |
| 48 | * - If node deletion call/return overlaps with the call to |
| 49 | * cds_ja_range_lookup() and return from cds_ja_range_lock(), the node |
| 50 | * may or may not be found by each of cds_ja_range_lookup() and |
| 51 | * cds_ja_range_lock(). |
| 52 | */ |
| 53 | |
| 54 | /* |
| 55 | * Discussion about order of lookup/lock vs allocated node add. Assuming |
| 56 | * no concurrent delete. |
| 57 | * |
| 58 | * - If node add returns before call to |
| 59 | * cds_ja_range_lookup(), the node will be found by lookup. |
| 60 | * - If node add is called after cds_ja_range_lookup returns, the node |
| 61 | * will not be found by lookup. |
| 62 | * - If node add call/return overlaps with the call to and return from |
| 63 | * cds_ja_range_lookup(), the node may or may not be found. |
| 64 | * - If node add call/return overlaps with call to cds_ja_range_lookup() |
| 65 | * and return from cds_ja_range_lock(), in the specific case where |
| 66 | * cds_ja_range_lookup() _does_ succeed, then cds_ja_range_lock() will |
| 67 | * succeed (still assuming no concurrent deletion). |
| 68 | */ |
| 69 | |
| 70 | /* |
| 71 | * Discussion: concurrent deletion of contiguous allocated ranges. |
| 72 | * |
| 73 | * Ensuring that merge of contiguous free ranges is always performed, we |
| 74 | * need to ensure locking of concurrent removal of contiguous allocated |
| 75 | * ranges one with respect to another. This is done by locking the |
| 76 | * ranges prior to and after the range to remove, even if that range is |
| 77 | * allocated. This serializes removal of contiguous ranges. The only |
| 78 | * cases for which there is no range to lock is when removing an |
| 79 | * allocated range starting at 0, and/or ending at the end of the key |
| 80 | * space. |
| 81 | */ |
| 82 | |
| 83 | /* |
| 84 | * Discussion of the type state transitions. |
| 85 | * |
| 86 | * State transitions of "type" always go from either: |
| 87 | * |
| 88 | * CDS_JA_RANGE_FREE -> CDS_JA_RANGE_REMOVED |
| 89 | * or |
| 90 | * CDS_JA_RANGE_ALLOCATED -> CDS_JA_RANGE_REMOVED |
| 91 | * |
| 92 | * A range type never changes otherwise. |
| 93 | */ |
| 94 | |
| 95 | |
| 96 | struct cds_ja_range *cds_ja_range_lookup(struct cds_ja *ja, uint64_t key) |
| 97 | { |
| 98 | struct cds_ja_node *node, *last_node; |
| 99 | struct cds_ja_range *range; |
| 100 | |
| 101 | node = cds_ja_lookup_below_equal(ja, key, NULL); |
| 102 | assert(node); |
| 103 | /* |
| 104 | * Get the last of duplicate chain. Adding a node to Judy array |
| 105 | * duplicates inserts them at the end of the chain. |
| 106 | */ |
| 107 | cds_ja_for_each_duplicate_rcu(node) |
| 108 | last_node = node; |
| 109 | range = caa_container_of(last_node, struct cds_ja_range, ja_node); |
| 110 | /* |
| 111 | * If last node in the duplicates is removed or free, we can |
| 112 | * consider that either a removal or add operation is in |
| 113 | * progress, or removal is the last completed operation to |
| 114 | * update this range. We can therefore consider that this area |
| 115 | * is not allocated. |
| 116 | */ |
| 117 | if (range->type != CDS_JA_RANGE_ALLOCATED) |
| 118 | return NULL; |
| 119 | /* |
| 120 | * We found an allocated range. We can return it for use with |
| 121 | * RCU read-side protection for existence. However, we have no |
| 122 | * mutual exclusion against removal at this point. |
| 123 | */ |
| 124 | return range; |
| 125 | } |
| 126 | |
| 127 | /* |
| 128 | * Provide mutual exclusion against removal. |
| 129 | */ |
| 130 | struct cds_ja_range *cds_ja_range_lock(struct cds_ja_range *range) |
| 131 | { |
| 132 | pthread_mutex_lock(&range->lock); |
| 133 | |
| 134 | if (range->type == CDS_JA_RANGE_REMOVED) |
| 135 | goto removed; |
| 136 | return range; |
| 137 | |
| 138 | removed: |
| 139 | pthread_mutex_unlock(&range->lock); |
| 140 | return NULL; |
| 141 | } |
| 142 | |
| 143 | void cds_ja_range_unlock(struct cds_ja_range *range) |
| 144 | { |
| 145 | pthread_mutex_unlock(&range->lock); |
| 146 | } |
| 147 | |
| 148 | static |
| 149 | struct cds_ja_range *range_create( |
| 150 | uint64_t start, /* inclusive */ |
| 151 | uint64_t end, /* inclusive */ |
| 152 | enum cds_ja_range_type type) |
| 153 | { |
| 154 | struct cds_ja_range *range; |
| 155 | |
| 156 | range = calloc(sizeof(*range), 1); |
| 157 | if (!range) |
| 158 | return NULL; |
| 159 | range->start = start; |
| 160 | range->end = end; |
| 161 | range->type = type; |
| 162 | pthread_mutex_init(&range->lock, NULL); |
| 163 | return range; |
| 164 | } |
| 165 | |
| 166 | static |
| 167 | void free_range_cb(struct rcu_head *head) |
| 168 | { |
| 169 | struct cds_ja_range *range = |
| 170 | caa_container_of(head, struct cds_ja_range, head); |
| 171 | free(range); |
| 172 | } |
| 173 | |
| 174 | static |
| 175 | void free_range(struct cds_ja_range *range) |
| 176 | { |
| 177 | free(range); |
| 178 | } |
| 179 | |
| 180 | static |
| 181 | void rcu_free_range(struct cds_ja *ja, struct cds_ja_range *range) |
| 182 | { |
| 183 | cds_lfht_rcu_flavor(ja->ht)->update_call_rcu(&range->head, |
| 184 | free_range_cb); |
| 185 | } |
| 186 | |
| 187 | struct cds_ja_range *cds_ja_range_add(struct cds_ja *ja, |
| 188 | uint64_t start, /* inclusive */ |
| 189 | uint64_t end) /* inclusive */ |
| 190 | { |
| 191 | struct cds_ja_node *old_node, *old_node_end; |
| 192 | struct cds_ja_range *old_range, *old_range_end, *new_range, *ranges[3]; |
| 193 | unsigned int nr_ranges, i; |
| 194 | int ret; |
| 195 | |
| 196 | retry: |
| 197 | /* |
| 198 | * Find if requested range is entirely contained within a single |
| 199 | * free range. |
| 200 | */ |
| 201 | old_node = cds_ja_lookup_below_equal(ja, start, NULL); |
| 202 | assert(old_node); |
| 203 | |
| 204 | old_range = caa_container_of(old_node, struct cds_ja_range, ja_node); |
| 205 | switch (CMM_LOAD_SHARED(old_range->type)) { |
| 206 | case CDS_JA_RANGE_ALLOCATED: |
| 207 | return NULL; |
| 208 | case CDS_JA_RANGE_FREE: |
| 209 | break; |
| 210 | case CDS_JA_RANGE_REMOVED: |
| 211 | goto retry; |
| 212 | } |
| 213 | |
| 214 | old_node_end = cds_ja_lookup_below_equal(ja, end, NULL); |
| 215 | assert(old_node_end); |
| 216 | old_range_end = caa_container_of(old_node_end, |
| 217 | struct cds_ja_range, ja_node); |
| 218 | if (old_range_end != old_range) { |
| 219 | switch (CMM_LOAD_SHARED(old_range->type)) { |
| 220 | case CDS_JA_RANGE_ALLOCATED: |
| 221 | case CDS_JA_RANGE_FREE: /* fall-through */ |
| 222 | return NULL; |
| 223 | case CDS_JA_RANGE_REMOVED: |
| 224 | goto retry; |
| 225 | } |
| 226 | } |
| 227 | |
| 228 | pthread_mutex_lock(&old_range->lock); |
| 229 | |
| 230 | if (old_range->type == CDS_JA_RANGE_REMOVED) { |
| 231 | pthread_mutex_unlock(&old_range->lock); |
| 232 | goto retry; |
| 233 | } |
| 234 | |
| 235 | /* Create replacement ranges: at most 2 free and 1 allocated */ |
| 236 | if (start == old_range->start) { |
| 237 | if (end == old_range->end) { |
| 238 | /* 1 range */ |
| 239 | ranges[0] = new_range = range_create(start, end, |
| 240 | CDS_JA_RANGE_ALLOCATED); |
| 241 | nr_ranges = 1; |
| 242 | } else { |
| 243 | /* 2 ranges */ |
| 244 | ranges[0] = new_range = range_create(start, end, |
| 245 | CDS_JA_RANGE_ALLOCATED); |
| 246 | ranges[1] = range_create(end + 1, old_range->end, |
| 247 | CDS_JA_RANGE_FREE); |
| 248 | nr_ranges = 2; |
| 249 | } |
| 250 | } else { |
| 251 | if (end == old_range->end) { |
| 252 | /* 2 ranges */ |
| 253 | ranges[0] = range_create(old_range->start, start - 1, |
| 254 | CDS_JA_RANGE_FREE); |
| 255 | ranges[1] = new_range = range_create(start, end, |
| 256 | CDS_JA_RANGE_ALLOCATED); |
| 257 | nr_ranges = 2; |
| 258 | } else { |
| 259 | /* 3 ranges */ |
| 260 | ranges[0] = range_create(old_range->start, start - 1, |
| 261 | CDS_JA_RANGE_FREE); |
| 262 | ranges[1] = new_range = range_create(start, end, |
| 263 | CDS_JA_RANGE_ALLOCATED); |
| 264 | ranges[2] = range_create(end + 1, old_range->end, |
| 265 | CDS_JA_RANGE_FREE); |
| 266 | nr_ranges = 3; |
| 267 | } |
| 268 | } |
| 269 | |
| 270 | /* Add replacement ranges to Judy array */ |
| 271 | for (i = 0; i < nr_ranges; i++) { |
| 272 | ret = cds_ja_add(ja, ranges[i]->start, &ranges[i]->ja_node); |
| 273 | assert(!ret); |
| 274 | } |
| 275 | |
| 276 | /* |
| 277 | * We add replacement ranges _before_ removing old ranges, so |
| 278 | * concurrent traversals will always see one or the other. This |
| 279 | * is OK because we temporarily have a duplicate key, and Judy |
| 280 | * arrays provide key existence guarantee for lookups performed |
| 281 | * concurrently with add followed by del of duplicate keys. |
| 282 | */ |
| 283 | |
| 284 | /* Remove old free range */ |
| 285 | ret = cds_ja_del(ja, old_range->start, &old_range->ja_node); |
| 286 | assert(!ret); |
| 287 | old_range->type = CDS_JA_RANGE_REMOVED; |
| 288 | pthread_mutex_unlock(&old_range->lock); |
| 289 | |
| 290 | rcu_free_range(ja, old_range); |
| 291 | |
| 292 | return new_range; |
| 293 | } |
| 294 | |
| 295 | int cds_ja_range_del(struct cds_ja *ja, struct cds_ja_range *range) |
| 296 | { |
| 297 | struct cds_ja_node *prev_node, *next_node; |
| 298 | struct cds_ja_range *new_range; |
| 299 | struct cds_ja_range *merge_ranges[3], *lock_ranges[3]; |
| 300 | unsigned int nr_merge, nr_lock, i; |
| 301 | uint64_t start, end; |
| 302 | int ret; |
| 303 | |
| 304 | retry: |
| 305 | nr_merge = 0; |
| 306 | nr_lock = 0; |
| 307 | prev_node = cds_ja_lookup_below_equal(ja, range->start - 1, NULL); |
| 308 | if (prev_node) { |
| 309 | struct cds_ja_range *prev_range; |
| 310 | |
| 311 | prev_range = caa_container_of(prev_node, |
| 312 | struct cds_ja_range, ja_node); |
| 313 | lock_ranges[nr_lock++] = prev_range; |
| 314 | if (prev_range->type != CDS_JA_RANGE_ALLOCATED) |
| 315 | merge_ranges[nr_merge++] = prev_range; |
| 316 | } |
| 317 | |
| 318 | lock_ranges[nr_lock++] = range; |
| 319 | merge_ranges[nr_merge++] = range; |
| 320 | |
| 321 | next_node = cds_ja_lookup_above_equal(ja, range->end + 1, NULL); |
| 322 | if (next_node) { |
| 323 | struct cds_ja_range *next_range; |
| 324 | |
| 325 | next_range = caa_container_of(next_node, |
| 326 | struct cds_ja_range, ja_node); |
| 327 | lock_ranges[nr_lock++] = next_range; |
| 328 | if (next_range->type != CDS_JA_RANGE_ALLOCATED) |
| 329 | merge_ranges[nr_merge++] = next_range; |
| 330 | } |
| 331 | |
| 332 | /* Acquire locks in increasing key order for range merge */ |
| 333 | for (i = 0; i < nr_lock; i++) |
| 334 | pthread_mutex_lock(&lock_ranges[i]->lock); |
| 335 | /* Ensure they are valid */ |
| 336 | for (i = 0; i < nr_lock; i++) { |
| 337 | if (lock_ranges[i]->type == CDS_JA_RANGE_REMOVED) |
| 338 | goto unlock_retry; |
| 339 | } |
| 340 | |
| 341 | /* Create new free range */ |
| 342 | start = merge_ranges[0]->start; |
| 343 | end = merge_ranges[nr_merge - 1]->end; |
| 344 | new_range = range_create(start, end, CDS_JA_RANGE_FREE); |
| 345 | ret = cds_ja_add(ja, start, &new_range->ja_node); |
| 346 | assert(!ret); |
| 347 | |
| 348 | /* Remove old ranges */ |
| 349 | for (i = 0; i < nr_merge; i++) { |
| 350 | ret = cds_ja_del(ja, merge_ranges[i]->start, |
| 351 | &merge_ranges[i]->ja_node); |
| 352 | assert(!ret); |
| 353 | merge_ranges[i]->type = CDS_JA_RANGE_REMOVED; |
| 354 | } |
| 355 | for (i = 0; i < nr_lock; i++) |
| 356 | pthread_mutex_unlock(&lock_ranges[i]->lock); |
| 357 | /* Free old merged ranges */ |
| 358 | for (i = 0; i < nr_merge; i++) |
| 359 | rcu_free_range(ja, merge_ranges[i]); |
| 360 | |
| 361 | return 0; |
| 362 | |
| 363 | /* retry paths */ |
| 364 | unlock_retry: |
| 365 | for (i = 0; i < nr_lock; i++) |
| 366 | pthread_mutex_unlock(&lock_ranges[i]->lock); |
| 367 | goto retry; |
| 368 | } |
| 369 | |
| 370 | int cds_ja_range_init(struct cds_ja *ja) |
| 371 | { |
| 372 | struct cds_ja_node *node; |
| 373 | struct cds_ja_range *range; |
| 374 | int ret; |
| 375 | |
| 376 | /* |
| 377 | * Sanity check: should be empty. |
| 378 | */ |
| 379 | node = cds_ja_lookup_above_equal(ja, 0, NULL); |
| 380 | if (node) |
| 381 | return -EINVAL; |
| 382 | range = range_create(0, UINT64_MAX, CDS_JA_RANGE_FREE); |
| 383 | if (!range) |
| 384 | return -EINVAL; |
| 385 | ret = cds_ja_add(ja, 0, &range->ja_node); |
| 386 | return ret; |
| 387 | } |
| 388 | |
| 389 | int cds_ja_range_fini(struct cds_ja *ja) |
| 390 | { |
| 391 | uint64_t key; |
| 392 | struct cds_ja_node *ja_node; |
| 393 | int ret = 0; |
| 394 | |
| 395 | cds_ja_for_each_key_rcu(ja, key, ja_node) { |
| 396 | struct cds_ja_node *tmp_node; |
| 397 | |
| 398 | cds_ja_for_each_duplicate_safe_rcu(ja_node, tmp_node) { |
| 399 | struct cds_ja_range *range; |
| 400 | |
| 401 | range = caa_container_of(ja_node, |
| 402 | struct cds_ja_range, ja_node); |
| 403 | ret = cds_ja_del(ja, key, &range->ja_node); |
| 404 | if (ret) { |
| 405 | goto end; |
| 406 | } |
| 407 | /* Alone using Judy array, OK to free now */ |
| 408 | free_range(range); |
| 409 | } |
| 410 | } |
| 411 | end: |
| 412 | return ret; |
| 413 | } |