1#ifndef _LINUX_RCULIST_H 2#define _LINUX_RCULIST_H 3 4#ifdef __KERNEL__ 5 6/* 7 * RCU-protected list version 8 */ 9#include <linux/list.h> 10#include <linux/rcupdate.h> 11 12/* 13 * Insert a new entry between two known consecutive entries. 14 * 15 * This is only for internal list manipulation where we know 16 * the prev/next entries already! 17 */ 18static inline void __list_add_rcu(struct list_head *new, 19 struct list_head *prev, struct list_head *next) 20{ 21 new->next = next; 22 new->prev = prev; 23 rcu_assign_pointer(prev->next, new); 24 next->prev = new; 25} 26 27/** 28 * list_add_rcu - add a new entry to rcu-protected list 29 * @new: new entry to be added 30 * @head: list head to add it after 31 * 32 * Insert a new entry after the specified head. 33 * This is good for implementing stacks. 34 * 35 * The caller must take whatever precautions are necessary 36 * (such as holding appropriate locks) to avoid racing 37 * with another list-mutation primitive, such as list_add_rcu() 38 * or list_del_rcu(), running on this same list. 39 * However, it is perfectly legal to run concurrently with 40 * the _rcu list-traversal primitives, such as 41 * list_for_each_entry_rcu(). 42 */ 43static inline void list_add_rcu(struct list_head *new, struct list_head *head) 44{ 45 __list_add_rcu(new, head, head->next); 46} 47 48/** 49 * list_add_tail_rcu - add a new entry to rcu-protected list 50 * @new: new entry to be added 51 * @head: list head to add it before 52 * 53 * Insert a new entry before the specified head. 54 * This is useful for implementing queues. 55 * 56 * The caller must take whatever precautions are necessary 57 * (such as holding appropriate locks) to avoid racing 58 * with another list-mutation primitive, such as list_add_tail_rcu() 59 * or list_del_rcu(), running on this same list. 60 * However, it is perfectly legal to run concurrently with 61 * the _rcu list-traversal primitives, such as 62 * list_for_each_entry_rcu(). 63 */ 64static inline void list_add_tail_rcu(struct list_head *new, 65 struct list_head *head) 66{ 67 __list_add_rcu(new, head->prev, head); 68} 69 70/** 71 * list_del_rcu - deletes entry from list without re-initialization 72 * @entry: the element to delete from the list. 73 * 74 * Note: list_empty() on entry does not return true after this, 75 * the entry is in an undefined state. It is useful for RCU based 76 * lockfree traversal. 77 * 78 * In particular, it means that we can not poison the forward 79 * pointers that may still be used for walking the list. 80 * 81 * The caller must take whatever precautions are necessary 82 * (such as holding appropriate locks) to avoid racing 83 * with another list-mutation primitive, such as list_del_rcu() 84 * or list_add_rcu(), running on this same list. 85 * However, it is perfectly legal to run concurrently with 86 * the _rcu list-traversal primitives, such as 87 * list_for_each_entry_rcu(). 88 * 89 * Note that the caller is not permitted to immediately free 90 * the newly deleted entry. Instead, either synchronize_rcu() 91 * or call_rcu() must be used to defer freeing until an RCU 92 * grace period has elapsed. 93 */ 94static inline void list_del_rcu(struct list_head *entry) 95{ 96 __list_del(entry->prev, entry->next); 97 entry->prev = LIST_POISON2; 98} 99 100/** 101 * hlist_del_init_rcu - deletes entry from hash list with re-initialization 102 * @n: the element to delete from the hash list. 103 * 104 * Note: list_unhashed() on the node return true after this. It is 105 * useful for RCU based read lockfree traversal if the writer side 106 * must know if the list entry is still hashed or already unhashed. 107 * 108 * In particular, it means that we can not poison the forward pointers 109 * that may still be used for walking the hash list and we can only 110 * zero the pprev pointer so list_unhashed() will return true after 111 * this. 112 * 113 * The caller must take whatever precautions are necessary (such as 114 * holding appropriate locks) to avoid racing with another 115 * list-mutation primitive, such as hlist_add_head_rcu() or 116 * hlist_del_rcu(), running on this same list. However, it is 117 * perfectly legal to run concurrently with the _rcu list-traversal 118 * primitives, such as hlist_for_each_entry_rcu(). 119 */ 120static inline void hlist_del_init_rcu(struct hlist_node *n) 121{ 122 if (!hlist_unhashed(n)) { 123 __hlist_del(n); 124 n->pprev = NULL; 125 } 126} 127 128/** 129 * list_replace_rcu - replace old entry by new one 130 * @old : the element to be replaced 131 * @new : the new element to insert 132 * 133 * The @old entry will be replaced with the @new entry atomically. 134 * Note: @old should not be empty. 135 */ 136static inline void list_replace_rcu(struct list_head *old, 137 struct list_head *new) 138{ 139 new->next = old->next; 140 new->prev = old->prev; 141 rcu_assign_pointer(new->prev->next, new); 142 new->next->prev = new; 143 old->prev = LIST_POISON2; 144} 145 146/** 147 * list_splice_init_rcu - splice an RCU-protected list into an existing list. 148 * @list: the RCU-protected list to splice 149 * @head: the place in the list to splice the first list into 150 * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ... 151 * 152 * @head can be RCU-read traversed concurrently with this function. 153 * 154 * Note that this function blocks. 155 * 156 * Important note: the caller must take whatever action is necessary to 157 * prevent any other updates to @head. In principle, it is possible 158 * to modify the list as soon as sync() begins execution. 159 * If this sort of thing becomes necessary, an alternative version 160 * based on call_rcu() could be created. But only if -really- 161 * needed -- there is no shortage of RCU API members. 162 */ 163static inline void list_splice_init_rcu(struct list_head *list, 164 struct list_head *head, 165 void (*sync)(void)) 166{ 167 struct list_head *first = list->next; 168 struct list_head *last = list->prev; 169 struct list_head *at = head->next; 170 171 if (list_empty(head)) 172 return; 173 174 /* "first" and "last" tracking list, so initialize it. */ 175 176 INIT_LIST_HEAD(list); 177 178 /* 179 * At this point, the list body still points to the source list. 180 * Wait for any readers to finish using the list before splicing 181 * the list body into the new list. Any new readers will see 182 * an empty list. 183 */ 184 185 sync(); 186 187 /* 188 * Readers are finished with the source list, so perform splice. 189 * The order is important if the new list is global and accessible 190 * to concurrent RCU readers. Note that RCU readers are not 191 * permitted to traverse the prev pointers without excluding 192 * this function. 193 */ 194 195 last->next = at; 196 rcu_assign_pointer(head->next, first); 197 first->prev = head; 198 at->prev = last; 199} 200 201/** 202 * list_entry_rcu - get the struct for this entry 203 * @ptr: the &struct list_head pointer. 204 * @type: the type of the struct this is embedded in. 205 * @member: the name of the list_struct within the struct. 206 * 207 * This primitive may safely run concurrently with the _rcu list-mutation 208 * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). 209 */ 210#define list_entry_rcu(ptr, type, member) \ 211 container_of(rcu_dereference_raw(ptr), type, member) 212 213/** 214 * list_first_entry_rcu - get the first element from a list 215 * @ptr: the list head to take the element from. 216 * @type: the type of the struct this is embedded in. 217 * @member: the name of the list_struct within the struct. 218 * 219 * Note, that list is expected to be not empty. 220 * 221 * This primitive may safely run concurrently with the _rcu list-mutation 222 * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). 223 */ 224#define list_first_entry_rcu(ptr, type, member) \ 225 list_entry_rcu((ptr)->next, type, member) 226 227#define __list_for_each_rcu(pos, head) \ 228 for (pos = rcu_dereference_raw((head)->next); \ 229 pos != (head); \ 230 pos = rcu_dereference_raw(pos->next)) 231 232/** 233 * list_for_each_entry_rcu - iterate over rcu list of given type 234 * @pos: the type * to use as a loop cursor. 235 * @head: the head for your list. 236 * @member: the name of the list_struct within the struct. 237 * 238 * This list-traversal primitive may safely run concurrently with 239 * the _rcu list-mutation primitives such as list_add_rcu() 240 * as long as the traversal is guarded by rcu_read_lock(). 241 */ 242#define list_for_each_entry_rcu(pos, head, member) \ 243 for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \ 244 prefetch(pos->member.next), &pos->member != (head); \ 245 pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) 246 247 248/** 249 * list_for_each_continue_rcu 250 * @pos: the &struct list_head to use as a loop cursor. 251 * @head: the head for your list. 252 * 253 * Iterate over an rcu-protected list, continuing after current point. 254 * 255 * This list-traversal primitive may safely run concurrently with 256 * the _rcu list-mutation primitives such as list_add_rcu() 257 * as long as the traversal is guarded by rcu_read_lock(). 258 */ 259#define list_for_each_continue_rcu(pos, head) \ 260 for ((pos) = rcu_dereference_raw((pos)->next); \ 261 prefetch((pos)->next), (pos) != (head); \ 262 (pos) = rcu_dereference_raw((pos)->next)) 263 264/** 265 * list_for_each_entry_continue_rcu - continue iteration over list of given type 266 * @pos: the type * to use as a loop cursor. 267 * @head: the head for your list. 268 * @member: the name of the list_struct within the struct. 269 * 270 * Continue to iterate over list of given type, continuing after 271 * the current position. 272 */ 273#define list_for_each_entry_continue_rcu(pos, head, member) \ 274 for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \ 275 prefetch(pos->member.next), &pos->member != (head); \ 276 pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) 277 278/** 279 * hlist_del_rcu - deletes entry from hash list without re-initialization 280 * @n: the element to delete from the hash list. 281 * 282 * Note: list_unhashed() on entry does not return true after this, 283 * the entry is in an undefined state. It is useful for RCU based 284 * lockfree traversal. 285 * 286 * In particular, it means that we can not poison the forward 287 * pointers that may still be used for walking the hash list. 288 * 289 * The caller must take whatever precautions are necessary 290 * (such as holding appropriate locks) to avoid racing 291 * with another list-mutation primitive, such as hlist_add_head_rcu() 292 * or hlist_del_rcu(), running on this same list. 293 * However, it is perfectly legal to run concurrently with 294 * the _rcu list-traversal primitives, such as 295 * hlist_for_each_entry(). 296 */ 297static inline void hlist_del_rcu(struct hlist_node *n) 298{ 299 __hlist_del(n); 300 n->pprev = LIST_POISON2; 301} 302 303/** 304 * hlist_replace_rcu - replace old entry by new one 305 * @old : the element to be replaced 306 * @new : the new element to insert 307 * 308 * The @old entry will be replaced with the @new entry atomically. 309 */ 310static inline void hlist_replace_rcu(struct hlist_node *old, 311 struct hlist_node *new) 312{ 313 struct hlist_node *next = old->next; 314 315 new->next = next; 316 new->pprev = old->pprev; 317 rcu_assign_pointer(*new->pprev, new); 318 if (next) 319 new->next->pprev = &new->next; 320 old->pprev = LIST_POISON2; 321} 322 323/** 324 * hlist_add_head_rcu 325 * @n: the element to add to the hash list. 326 * @h: the list to add to. 327 * 328 * Description: 329 * Adds the specified element to the specified hlist, 330 * while permitting racing traversals. 331 * 332 * The caller must take whatever precautions are necessary 333 * (such as holding appropriate locks) to avoid racing 334 * with another list-mutation primitive, such as hlist_add_head_rcu() 335 * or hlist_del_rcu(), running on this same list. 336 * However, it is perfectly legal to run concurrently with 337 * the _rcu list-traversal primitives, such as 338 * hlist_for_each_entry_rcu(), used to prevent memory-consistency 339 * problems on Alpha CPUs. Regardless of the type of CPU, the 340 * list-traversal primitive must be guarded by rcu_read_lock(). 341 */ 342static inline void hlist_add_head_rcu(struct hlist_node *n, 343 struct hlist_head *h) 344{ 345 struct hlist_node *first = h->first; 346 347 n->next = first; 348 n->pprev = &h->first; 349 rcu_assign_pointer(h->first, n); 350 if (first) 351 first->pprev = &n->next; 352} 353 354/** 355 * hlist_add_before_rcu 356 * @n: the new element to add to the hash list. 357 * @next: the existing element to add the new element before. 358 * 359 * Description: 360 * Adds the specified element to the specified hlist 361 * before the specified node while permitting racing traversals. 362 * 363 * The caller must take whatever precautions are necessary 364 * (such as holding appropriate locks) to avoid racing 365 * with another list-mutation primitive, such as hlist_add_head_rcu() 366 * or hlist_del_rcu(), running on this same list. 367 * However, it is perfectly legal to run concurrently with 368 * the _rcu list-traversal primitives, such as 369 * hlist_for_each_entry_rcu(), used to prevent memory-consistency 370 * problems on Alpha CPUs. 371 */ 372static inline void hlist_add_before_rcu(struct hlist_node *n, 373 struct hlist_node *next) 374{ 375 n->pprev = next->pprev; 376 n->next = next; 377 rcu_assign_pointer(*(n->pprev), n); 378 next->pprev = &n->next; 379} 380 381/** 382 * hlist_add_after_rcu 383 * @prev: the existing element to add the new element after. 384 * @n: the new element to add to the hash list. 385 * 386 * Description: 387 * Adds the specified element to the specified hlist 388 * after the specified node while permitting racing traversals. 389 * 390 * The caller must take whatever precautions are necessary 391 * (such as holding appropriate locks) to avoid racing 392 * with another list-mutation primitive, such as hlist_add_head_rcu() 393 * or hlist_del_rcu(), running on this same list. 394 * However, it is perfectly legal to run concurrently with 395 * the _rcu list-traversal primitives, such as 396 * hlist_for_each_entry_rcu(), used to prevent memory-consistency 397 * problems on Alpha CPUs. 398 */ 399static inline void hlist_add_after_rcu(struct hlist_node *prev, 400 struct hlist_node *n) 401{ 402 n->next = prev->next; 403 n->pprev = &prev->next; 404 rcu_assign_pointer(prev->next, n); 405 if (n->next) 406 n->next->pprev = &n->next; 407} 408 409#define __hlist_for_each_rcu(pos, head) \ 410 for (pos = rcu_dereference((head)->first); \ 411 pos && ({ prefetch(pos->next); 1; }); \ 412 pos = rcu_dereference(pos->next)) 413 414/** 415 * hlist_for_each_entry_rcu - iterate over rcu list of given type 416 * @tpos: the type * to use as a loop cursor. 417 * @pos: the &struct hlist_node to use as a loop cursor. 418 * @head: the head for your list. 419 * @member: the name of the hlist_node within the struct. 420 * 421 * This list-traversal primitive may safely run concurrently with 422 * the _rcu list-mutation primitives such as hlist_add_head_rcu() 423 * as long as the traversal is guarded by rcu_read_lock(). 424 */ 425#define hlist_for_each_entry_rcu(tpos, pos, head, member) \ 426 for (pos = rcu_dereference_raw((head)->first); \ 427 pos && ({ prefetch(pos->next); 1; }) && \ 428 ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ 429 pos = rcu_dereference_raw(pos->next)) 430 431/** 432 * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type 433 * @tpos: the type * to use as a loop cursor. 434 * @pos: the &struct hlist_node to use as a loop cursor. 435 * @head: the head for your list. 436 * @member: the name of the hlist_node within the struct. 437 * 438 * This list-traversal primitive may safely run concurrently with 439 * the _rcu list-mutation primitives such as hlist_add_head_rcu() 440 * as long as the traversal is guarded by rcu_read_lock(). 441 */ 442#define hlist_for_each_entry_rcu_bh(tpos, pos, head, member) \ 443 for (pos = rcu_dereference_bh((head)->first); \ 444 pos && ({ prefetch(pos->next); 1; }) && \ 445 ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ 446 pos = rcu_dereference_bh(pos->next)) 447 448/** 449 * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point 450 * @tpos: the type * to use as a loop cursor. 451 * @pos: the &struct hlist_node to use as a loop cursor. 452 * @member: the name of the hlist_node within the struct. 453 */ 454#define hlist_for_each_entry_continue_rcu(tpos, pos, member) \ 455 for (pos = rcu_dereference((pos)->next); \ 456 pos && ({ prefetch(pos->next); 1; }) && \ 457 ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ 458 pos = rcu_dereference(pos->next)) 459 460/** 461 * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point 462 * @tpos: the type * to use as a loop cursor. 463 * @pos: the &struct hlist_node to use as a loop cursor. 464 * @member: the name of the hlist_node within the struct. 465 */ 466#define hlist_for_each_entry_continue_rcu_bh(tpos, pos, member) \ 467 for (pos = rcu_dereference_bh((pos)->next); \ 468 pos && ({ prefetch(pos->next); 1; }) && \ 469 ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ 470 pos = rcu_dereference_bh(pos->next)) 471 472 473#endif /* __KERNEL__ */ 474#endif 475