| 1 | /* |
| 2 | * Copyright (C) 2022 Jérémie Galarneau <jeremie.galarneau@efficios.com> |
| 3 | * |
| 4 | * SPDX-License-Identifier: LGPL-2.1-only |
| 5 | * |
| 6 | */ |
| 7 | |
| 8 | #ifndef LTTNG_URCU_H |
| 9 | #define LTTNG_URCU_H |
| 10 | |
| 11 | #define _LGPL_SOURCE |
| 12 | #include <common/exception.hpp> |
| 13 | #include <common/hashtable/hashtable.hpp> |
| 14 | #include <common/macros.hpp> |
| 15 | |
| 16 | #include <iterator> |
| 17 | #include <mutex> |
| 18 | #include <urcu.h> |
| 19 | #include <urcu/list.h> |
| 20 | #include <urcu/rculfhash.h> |
| 21 | |
| 22 | namespace lttng { |
| 23 | namespace urcu { |
| 24 | |
| 25 | namespace details { |
| 26 | /* |
| 27 | * Wrapper around an urcu read lock which satisfies the 'Mutex' named |
| 28 | * requirements of C++11. Satisfying those requirements facilitates the use of |
| 29 | * standard concurrency support library facilities. |
| 30 | * |
| 31 | * read_lock is under the details namespace since it is unlikely to be used |
| 32 | * directly by exception-safe code. See read_lock_guard. |
| 33 | */ |
| 34 | class read_lock { |
| 35 | public: |
| 36 | read_lock() = default; |
| 37 | ~read_lock() = default; |
| 38 | |
| 39 | /* "Not copyable" and "not moveable" Mutex requirements. */ |
| 40 | read_lock(const read_lock&) = delete; |
| 41 | read_lock(read_lock&&) = delete; |
| 42 | read_lock& operator=(read_lock&&) = delete; |
| 43 | read_lock& operator=(const read_lock&) = delete; |
| 44 | |
| 45 | void lock() |
| 46 | { |
| 47 | rcu_read_lock(); |
| 48 | } |
| 49 | |
| 50 | bool try_lock() |
| 51 | { |
| 52 | lock(); |
| 53 | return true; |
| 54 | } |
| 55 | |
| 56 | void unlock() |
| 57 | { |
| 58 | rcu_read_unlock(); |
| 59 | } |
| 60 | }; |
| 61 | } /* namespace details */ |
| 62 | |
| 63 | /* |
| 64 | * Provides the basic concept of std::lock_guard for rcu reader locks. |
| 65 | * |
| 66 | * The RCU reader lock is held for the duration of lock_guard's lifetime. |
| 67 | */ |
| 68 | class read_lock_guard { |
| 69 | public: |
| 70 | read_lock_guard() = default; |
| 71 | ~read_lock_guard() = default; |
| 72 | |
| 73 | read_lock_guard(const read_lock_guard&) = delete; |
| 74 | read_lock_guard(read_lock_guard&&) = delete; |
| 75 | read_lock_guard& operator=(read_lock_guard&&) = delete; |
| 76 | read_lock_guard& operator=(const read_lock_guard&) = delete; |
| 77 | |
| 78 | private: |
| 79 | details::read_lock _lock; |
| 80 | std::lock_guard<details::read_lock> _guard{ _lock }; |
| 81 | }; |
| 82 | |
| 83 | using unique_read_lock = std::unique_lock<details::read_lock>; |
| 84 | |
| 85 | namespace details { |
| 86 | |
| 87 | /* Implementation for types that contain a straight cds_lfht_node. */ |
| 88 | template <typename ContainedType, typename NodeType, NodeType ContainedType::*Member> |
| 89 | static typename std::enable_if<std::is_same<cds_lfht_node, NodeType>::value, ContainedType *>::type |
| 90 | get_element_from_node(cds_lfht_node& node) |
| 91 | { |
| 92 | return lttng::utils::container_of(&node, Member); |
| 93 | } |
| 94 | |
| 95 | /* Specialization for NodeType deriving from lttng_ht_node. */ |
| 96 | template <typename ContainedType, typename NodeType, NodeType ContainedType::*Member> |
| 97 | static typename std::enable_if<std::is_base_of<lttng_ht_node, NodeType>::value, ContainedType *>::type |
| 98 | get_element_from_node(cds_lfht_node& node) |
| 99 | { |
| 100 | return lttng_ht_node_container_of(&node, Member); |
| 101 | } |
| 102 | } /* namespace details */ |
| 103 | |
| 104 | /* |
| 105 | * The lfht_iteration_adapter class template wraps the liburcu lfht API to provide iteration |
| 106 | * capabilities. It allows users to iterate over a lock-free hash table with ranged-for semantics |
| 107 | * while holding the RCU read lock. The reader lock is held for the lifetime of the iteration |
| 108 | * adapter (i.e. not the lifetime of the iterators it provides). |
| 109 | */ |
| 110 | template <typename ContainedType, typename NodeType, NodeType ContainedType::*Member> |
| 111 | class lfht_iteration_adapter { |
| 112 | public: |
| 113 | /* Nested iterator class defines the iterator for lfht_iteration_adapter. */ |
| 114 | class iterator : public std::iterator<std::input_iterator_tag, std::uint64_t> { |
| 115 | /* Allow lfht_iteration_adapter to access private members of iterator. */ |
| 116 | friend lfht_iteration_adapter; |
| 117 | |
| 118 | public: |
| 119 | iterator(const iterator& other) = default; |
| 120 | iterator(iterator&& other) noexcept = default; |
| 121 | ~iterator() = default; |
| 122 | iterator& operator=(const iterator&) = delete; |
| 123 | iterator& operator=(iterator&&) noexcept = delete; |
| 124 | |
| 125 | /* Move to the next element in the hash table. */ |
| 126 | iterator& operator++() |
| 127 | { |
| 128 | cds_lfht_next(&_ht, &_it); |
| 129 | return *this; |
| 130 | } |
| 131 | |
| 132 | bool operator==(const iterator& other) const noexcept |
| 133 | { |
| 134 | /* Compare pointed nodes by address. */ |
| 135 | return other._it.node == _it.node; |
| 136 | } |
| 137 | |
| 138 | bool operator!=(const iterator& other) const noexcept |
| 139 | { |
| 140 | return !(*this == other); |
| 141 | } |
| 142 | |
| 143 | /* Dereference the iterator to access the contained element. */ |
| 144 | ContainedType *operator*() const |
| 145 | { |
| 146 | auto *node = _it.node; |
| 147 | |
| 148 | /* Throw an exception if dereferencing an end iterator. */ |
| 149 | if (!node) { |
| 150 | LTTNG_THROW_OUT_OF_RANGE( |
| 151 | "Dereferenced an iterator at the end of a liburcu hashtable"); |
| 152 | } |
| 153 | |
| 154 | /* Retrieve the element from the node. */ |
| 155 | return details::get_element_from_node<ContainedType, NodeType, Member>( |
| 156 | *node); |
| 157 | } |
| 158 | |
| 159 | protected: |
| 160 | iterator(cds_lfht& ht, const cds_lfht_iter& it) : _ht(ht), _it(it) |
| 161 | { |
| 162 | } |
| 163 | |
| 164 | /* Reference to the hash table being iterated over. */ |
| 165 | cds_lfht& _ht; |
| 166 | /* Native lfht iterator pointing to the current position. */ |
| 167 | cds_lfht_iter _it; |
| 168 | }; |
| 169 | |
| 170 | explicit lfht_iteration_adapter(cds_lfht& ht) : _ht(ht) |
| 171 | { |
| 172 | } |
| 173 | |
| 174 | /* Return an iterator to the beginning of the hash table. */ |
| 175 | iterator begin() const noexcept |
| 176 | { |
| 177 | cds_lfht_iter it; |
| 178 | |
| 179 | cds_lfht_first(&_ht, &it); |
| 180 | return iterator(_ht, it); |
| 181 | } |
| 182 | |
| 183 | /* Return an iterator to the end of the hash table. */ |
| 184 | iterator end() const noexcept |
| 185 | { |
| 186 | const cds_lfht_iter it = {}; |
| 187 | |
| 188 | return iterator(_ht, it); |
| 189 | } |
| 190 | |
| 191 | protected: |
| 192 | /* Reference to the hash table being iterated over. */ |
| 193 | cds_lfht& _ht; |
| 194 | /* RCU read lock held during the iteration. */ |
| 195 | const lttng::urcu::read_lock_guard read_lock; |
| 196 | }; |
| 197 | |
| 198 | /* |
| 199 | * The lfht_filtered_iteration_adapter class template wraps the liburcu lfht API to provide |
| 200 | * iteration capabilities over a result set. It allows users to iterate over a lock-free hash |
| 201 | * table's elements matching a given key with ranged-for semantics while holding the RCU read lock. |
| 202 | * The reader lock is held for the lifetime of the iteration adapter (i.e. not the lifetime of the |
| 203 | * iterators it provides). |
| 204 | */ |
| 205 | template <typename ContainedType, typename NodeType, NodeType ContainedType::*Member, typename KeyType> |
| 206 | class lfht_filtered_iteration_adapter |
| 207 | : public lfht_iteration_adapter<ContainedType, NodeType, Member> { |
| 208 | public: |
| 209 | /* Nested iterator class defines the iterator for lfht_filtered_iteration_adapter. */ |
| 210 | class iterator : public lfht_iteration_adapter<ContainedType, NodeType, Member>::iterator { |
| 211 | /* Allow lfht_filtered_iteration_adapter to access private members of iterator. */ |
| 212 | friend lfht_filtered_iteration_adapter; |
| 213 | |
| 214 | public: |
| 215 | iterator(const iterator& other) = default; |
| 216 | iterator(iterator&& other) noexcept = default; |
| 217 | ~iterator() = default; |
| 218 | iterator& operator=(const iterator&) = delete; |
| 219 | iterator& operator=(iterator&&) noexcept = delete; |
| 220 | |
| 221 | /* Move to the next element in the result set. */ |
| 222 | iterator& operator++() |
| 223 | { |
| 224 | LTTNG_ASSERT(this->_it.node); |
| 225 | /* NOLINTBEGIN(cppcoreguidelines-pro-type-const-cast) */ |
| 226 | cds_lfht_next_duplicate( |
| 227 | &this->_ht, |
| 228 | _match_function, |
| 229 | reinterpret_cast<void *>(const_cast<KeyType *>(_key)), |
| 230 | &this->_it); |
| 231 | /* NOLINTEND(cppcoreguidelines-pro-type-const-cast) */ |
| 232 | return *this; |
| 233 | } |
| 234 | |
| 235 | private: |
| 236 | iterator(cds_lfht& ht, |
| 237 | const cds_lfht_iter& it, |
| 238 | const KeyType *key, |
| 239 | cds_lfht_match_fct match_function) : |
| 240 | lfht_iteration_adapter<ContainedType, NodeType, Member>::iterator(ht, it), |
| 241 | _key(key), |
| 242 | _match_function(match_function) |
| 243 | { |
| 244 | } |
| 245 | |
| 246 | /* Only used to create an end iterator. */ |
| 247 | iterator(cds_lfht& ht, const cds_lfht_iter& it) : |
| 248 | lfht_iteration_adapter<ContainedType, NodeType, Member>::iterator(ht, it), |
| 249 | _key(nullptr), |
| 250 | _match_function(nullptr) |
| 251 | { |
| 252 | } |
| 253 | |
| 254 | const KeyType *_key; |
| 255 | const cds_lfht_match_fct _match_function; |
| 256 | }; |
| 257 | |
| 258 | explicit lfht_filtered_iteration_adapter(cds_lfht& ht, |
| 259 | const KeyType *key, |
| 260 | unsigned long key_hash, |
| 261 | cds_lfht_match_fct match_function) : |
| 262 | lfht_iteration_adapter<ContainedType, NodeType, Member>(ht), |
| 263 | _key(key), |
| 264 | _key_hash(key_hash), |
| 265 | _match_function(match_function) |
| 266 | { |
| 267 | } |
| 268 | |
| 269 | /* Return an iterator to the first result. */ |
| 270 | iterator begin() const noexcept |
| 271 | { |
| 272 | cds_lfht_iter it; |
| 273 | |
| 274 | /* NOLINTBEGIN(cppcoreguidelines-pro-type-const-cast) */ |
| 275 | cds_lfht_lookup(&this->_ht, |
| 276 | _key_hash, |
| 277 | _match_function, |
| 278 | reinterpret_cast<void *>(const_cast<KeyType *>(_key)), |
| 279 | &it); |
| 280 | /* NOLINTEND(cppcoreguidelines-pro-type-const-cast) */ |
| 281 | return iterator(this->_ht, it, _key, _match_function); |
| 282 | } |
| 283 | |
| 284 | iterator end() const noexcept |
| 285 | { |
| 286 | const cds_lfht_iter it = {}; |
| 287 | |
| 288 | return iterator(this->_ht, it); |
| 289 | } |
| 290 | |
| 291 | private: |
| 292 | const KeyType *_key; |
| 293 | const unsigned long _key_hash; |
| 294 | const cds_lfht_match_fct _match_function; |
| 295 | }; |
| 296 | |
| 297 | template <typename ContainedType, cds_list_head ContainedType::*Member> |
| 298 | class list_iteration_adapter { |
| 299 | public: |
| 300 | /* Nested iterator class defines the iterator for list_iteration_adapter. */ |
| 301 | class iterator : public std::iterator<std::input_iterator_tag, std::uint64_t> { |
| 302 | /* Allow list_iteration_adapter to access private members of iterator. */ |
| 303 | friend list_iteration_adapter; |
| 304 | |
| 305 | public: |
| 306 | iterator(const iterator& other) = default; |
| 307 | iterator(iterator&& other) noexcept = default; |
| 308 | ~iterator() = default; |
| 309 | iterator& operator=(const iterator&) = delete; |
| 310 | iterator& operator=(iterator&&) noexcept = delete; |
| 311 | |
| 312 | /* Move to the next element in the hash table. */ |
| 313 | iterator& operator++() |
| 314 | { |
| 315 | _node = _node_contents.next; |
| 316 | _node_contents = *_node; |
| 317 | return *this; |
| 318 | } |
| 319 | |
| 320 | bool operator==(const iterator& other) const noexcept |
| 321 | { |
| 322 | return other._node == _node; |
| 323 | } |
| 324 | |
| 325 | bool operator!=(const iterator& other) const noexcept |
| 326 | { |
| 327 | return !(*this == other); |
| 328 | } |
| 329 | |
| 330 | /* Dereference the iterator to access the contained element. */ |
| 331 | ContainedType *operator*() const |
| 332 | { |
| 333 | /* Retrieve the element from the node. */ |
| 334 | return lttng::utils::container_of(_node, Member); |
| 335 | } |
| 336 | |
| 337 | protected: |
| 338 | explicit iterator(const cds_list_head& node) : _node(&node), _node_contents(node) |
| 339 | { |
| 340 | } |
| 341 | |
| 342 | /* Current node. */ |
| 343 | const cds_list_head *_node; |
| 344 | /* Copy of node contents to allow safe deletion during the iteration. */ |
| 345 | cds_list_head _node_contents; |
| 346 | }; |
| 347 | |
| 348 | explicit list_iteration_adapter(const cds_list_head& list) : _list(list) |
| 349 | { |
| 350 | } |
| 351 | |
| 352 | /* Return an iterator to the beginning of the hash table. */ |
| 353 | iterator begin() const noexcept |
| 354 | { |
| 355 | return iterator(*_list.next); |
| 356 | } |
| 357 | |
| 358 | /* Return an iterator to the end of the hash table. */ |
| 359 | iterator end() const noexcept |
| 360 | { |
| 361 | return iterator(_list); |
| 362 | } |
| 363 | |
| 364 | protected: |
| 365 | /* Reference to the list being iterated over. */ |
| 366 | const cds_list_head& _list; |
| 367 | }; |
| 368 | |
| 369 | template <typename ContainedType, cds_list_head ContainedType::*Member> |
| 370 | class rcu_list_iteration_adapter : public list_iteration_adapter<ContainedType, Member> { |
| 371 | public: |
| 372 | /* Nested iterator class defines the iterator for rcu_list_iteration_adapter. */ |
| 373 | class iterator : public list_iteration_adapter<ContainedType, Member>::iterator { |
| 374 | /* Allow rcu_list_iteration_adapter to access private members of iterator. */ |
| 375 | friend rcu_list_iteration_adapter; |
| 376 | |
| 377 | public: |
| 378 | iterator(const iterator& other) = default; |
| 379 | iterator(iterator&& other) noexcept = default; |
| 380 | ~iterator() = default; |
| 381 | iterator& operator=(const iterator&) = delete; |
| 382 | iterator& operator=(iterator&&) noexcept = delete; |
| 383 | |
| 384 | /* Move to the next element in the hash table. */ |
| 385 | iterator& operator++() |
| 386 | { |
| 387 | this->_node = rcu_dereference(this->_node_contents.next); |
| 388 | this->_node_contents = *this->_node; |
| 389 | return *this; |
| 390 | } |
| 391 | |
| 392 | protected: |
| 393 | explicit iterator(const cds_list_head& node) : |
| 394 | list_iteration_adapter<ContainedType, Member>::iterator(node) |
| 395 | { |
| 396 | } |
| 397 | }; |
| 398 | |
| 399 | explicit rcu_list_iteration_adapter(const cds_list_head& list) : |
| 400 | list_iteration_adapter<ContainedType, Member>(list) |
| 401 | { |
| 402 | } |
| 403 | |
| 404 | /* Return an iterator to the beginning of the hash table. */ |
| 405 | iterator begin() const noexcept |
| 406 | { |
| 407 | return iterator(*rcu_dereference(this->_list.next)); |
| 408 | } |
| 409 | |
| 410 | /* Return an iterator to the end of the hash table. */ |
| 411 | iterator end() const noexcept |
| 412 | { |
| 413 | return iterator(this->_list); |
| 414 | } |
| 415 | |
| 416 | protected: |
| 417 | /* RCU read lock held during the iteration. */ |
| 418 | const lttng::urcu::read_lock_guard read_lock; |
| 419 | }; |
| 420 | |
| 421 | } /* namespace urcu */ |
| 422 | } /* namespace lttng */ |
| 423 | |
| 424 | #endif /* LTTNG_URCU_H */ |