1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef _LINUX_RCULIST_H |
3 | #define _LINUX_RCULIST_H |
4 | |
5 | #ifdef __KERNEL__ |
6 | |
7 | /* |
8 | * RCU-protected list version |
9 | */ |
10 | #include <linux/list.h> |
11 | #include <linux/rcupdate.h> |
12 | |
13 | /* |
14 | * Why is there no list_empty_rcu()? Because list_empty() serves this |
15 | * purpose. The list_empty() function fetches the RCU-protected pointer |
16 | * and compares it to the address of the list head, but neither dereferences |
17 | * this pointer itself nor provides this pointer to the caller. Therefore, |
18 | * it is not necessary to use rcu_dereference(), so that list_empty() can |
19 | * be used anywhere you would want to use a list_empty_rcu(). |
20 | */ |
21 | |
22 | /* |
23 | * INIT_LIST_HEAD_RCU - Initialize a list_head visible to RCU readers |
24 | * @list: list to be initialized |
25 | * |
26 | * You should instead use INIT_LIST_HEAD() for normal initialization and |
27 | * cleanup tasks, when readers have no access to the list being initialized. |
28 | * However, if the list being initialized is visible to readers, you |
29 | * need to keep the compiler from being too mischievous. |
30 | */ |
31 | static inline void INIT_LIST_HEAD_RCU(struct list_head *list) |
32 | { |
33 | WRITE_ONCE(list->next, list); |
34 | WRITE_ONCE(list->prev, list); |
35 | } |
36 | |
37 | /* |
38 | * return the ->next pointer of a list_head in an rcu safe |
39 | * way, we must not access it directly |
40 | */ |
41 | #define list_next_rcu(list) (*((struct list_head __rcu **)(&(list)->next))) |
42 | |
43 | /* |
44 | * Insert a new entry between two known consecutive entries. |
45 | * |
46 | * This is only for internal list manipulation where we know |
47 | * the prev/next entries already! |
48 | */ |
49 | static inline void __list_add_rcu(struct list_head *new, |
50 | struct list_head *prev, struct list_head *next) |
51 | { |
52 | if (!__list_add_valid(new, prev, next)) |
53 | return; |
54 | |
55 | new->next = next; |
56 | new->prev = prev; |
57 | rcu_assign_pointer(list_next_rcu(prev), new); |
58 | next->prev = new; |
59 | } |
60 | |
61 | /** |
62 | * list_add_rcu - add a new entry to rcu-protected list |
63 | * @new: new entry to be added |
64 | * @head: list head to add it after |
65 | * |
66 | * Insert a new entry after the specified head. |
67 | * This is good for implementing stacks. |
68 | * |
69 | * The caller must take whatever precautions are necessary |
70 | * (such as holding appropriate locks) to avoid racing |
71 | * with another list-mutation primitive, such as list_add_rcu() |
72 | * or list_del_rcu(), running on this same list. |
73 | * However, it is perfectly legal to run concurrently with |
74 | * the _rcu list-traversal primitives, such as |
75 | * list_for_each_entry_rcu(). |
76 | */ |
77 | static inline void list_add_rcu(struct list_head *new, struct list_head *head) |
78 | { |
79 | __list_add_rcu(new, head, head->next); |
80 | } |
81 | |
82 | /** |
83 | * list_add_tail_rcu - add a new entry to rcu-protected list |
84 | * @new: new entry to be added |
85 | * @head: list head to add it before |
86 | * |
87 | * Insert a new entry before the specified head. |
88 | * This is useful for implementing queues. |
89 | * |
90 | * The caller must take whatever precautions are necessary |
91 | * (such as holding appropriate locks) to avoid racing |
92 | * with another list-mutation primitive, such as list_add_tail_rcu() |
93 | * or list_del_rcu(), running on this same list. |
94 | * However, it is perfectly legal to run concurrently with |
95 | * the _rcu list-traversal primitives, such as |
96 | * list_for_each_entry_rcu(). |
97 | */ |
98 | static inline void list_add_tail_rcu(struct list_head *new, |
99 | struct list_head *head) |
100 | { |
101 | __list_add_rcu(new, head->prev, head); |
102 | } |
103 | |
104 | /** |
105 | * list_del_rcu - deletes entry from list without re-initialization |
106 | * @entry: the element to delete from the list. |
107 | * |
108 | * Note: list_empty() on entry does not return true after this, |
109 | * the entry is in an undefined state. It is useful for RCU based |
110 | * lockfree traversal. |
111 | * |
112 | * In particular, it means that we can not poison the forward |
113 | * pointers that may still be used for walking the list. |
114 | * |
115 | * The caller must take whatever precautions are necessary |
116 | * (such as holding appropriate locks) to avoid racing |
117 | * with another list-mutation primitive, such as list_del_rcu() |
118 | * or list_add_rcu(), running on this same list. |
119 | * However, it is perfectly legal to run concurrently with |
120 | * the _rcu list-traversal primitives, such as |
121 | * list_for_each_entry_rcu(). |
122 | * |
123 | * Note that the caller is not permitted to immediately free |
124 | * the newly deleted entry. Instead, either synchronize_rcu() |
125 | * or call_rcu() must be used to defer freeing until an RCU |
126 | * grace period has elapsed. |
127 | */ |
128 | static inline void list_del_rcu(struct list_head *entry) |
129 | { |
130 | __list_del_entry(entry); |
131 | entry->prev = LIST_POISON2; |
132 | } |
133 | |
134 | /** |
135 | * hlist_del_init_rcu - deletes entry from hash list with re-initialization |
136 | * @n: the element to delete from the hash list. |
137 | * |
138 | * Note: list_unhashed() on the node return true after this. It is |
139 | * useful for RCU based read lockfree traversal if the writer side |
140 | * must know if the list entry is still hashed or already unhashed. |
141 | * |
142 | * In particular, it means that we can not poison the forward pointers |
143 | * that may still be used for walking the hash list and we can only |
144 | * zero the pprev pointer so list_unhashed() will return true after |
145 | * this. |
146 | * |
147 | * The caller must take whatever precautions are necessary (such as |
148 | * holding appropriate locks) to avoid racing with another |
149 | * list-mutation primitive, such as hlist_add_head_rcu() or |
150 | * hlist_del_rcu(), running on this same list. However, it is |
151 | * perfectly legal to run concurrently with the _rcu list-traversal |
152 | * primitives, such as hlist_for_each_entry_rcu(). |
153 | */ |
154 | static inline void hlist_del_init_rcu(struct hlist_node *n) |
155 | { |
156 | if (!hlist_unhashed(n)) { |
157 | __hlist_del(n); |
158 | n->pprev = NULL; |
159 | } |
160 | } |
161 | |
162 | /** |
163 | * list_replace_rcu - replace old entry by new one |
164 | * @old : the element to be replaced |
165 | * @new : the new element to insert |
166 | * |
167 | * The @old entry will be replaced with the @new entry atomically. |
168 | * Note: @old should not be empty. |
169 | */ |
170 | static inline void list_replace_rcu(struct list_head *old, |
171 | struct list_head *new) |
172 | { |
173 | new->next = old->next; |
174 | new->prev = old->prev; |
175 | rcu_assign_pointer(list_next_rcu(new->prev), new); |
176 | new->next->prev = new; |
177 | old->prev = LIST_POISON2; |
178 | } |
179 | |
180 | /** |
181 | * __list_splice_init_rcu - join an RCU-protected list into an existing list. |
182 | * @list: the RCU-protected list to splice |
183 | * @prev: points to the last element of the existing list |
184 | * @next: points to the first element of the existing list |
185 | * @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
186 | * |
187 | * The list pointed to by @prev and @next can be RCU-read traversed |
188 | * concurrently with this function. |
189 | * |
190 | * Note that this function blocks. |
191 | * |
192 | * Important note: the caller must take whatever action is necessary to prevent |
193 | * any other updates to the existing list. In principle, it is possible to |
194 | * modify the list as soon as sync() begins execution. If this sort of thing |
195 | * becomes necessary, an alternative version based on call_rcu() could be |
196 | * created. But only if -really- needed -- there is no shortage of RCU API |
197 | * members. |
198 | */ |
199 | static inline void __list_splice_init_rcu(struct list_head *list, |
200 | struct list_head *prev, |
201 | struct list_head *next, |
202 | void (*sync)(void)) |
203 | { |
204 | struct list_head *first = list->next; |
205 | struct list_head *last = list->prev; |
206 | |
207 | /* |
208 | * "first" and "last" tracking list, so initialize it. RCU readers |
209 | * have access to this list, so we must use INIT_LIST_HEAD_RCU() |
210 | * instead of INIT_LIST_HEAD(). |
211 | */ |
212 | |
213 | INIT_LIST_HEAD_RCU(list); |
214 | |
215 | /* |
216 | * At this point, the list body still points to the source list. |
217 | * Wait for any readers to finish using the list before splicing |
218 | * the list body into the new list. Any new readers will see |
219 | * an empty list. |
220 | */ |
221 | |
222 | sync(); |
223 | |
224 | /* |
225 | * Readers are finished with the source list, so perform splice. |
226 | * The order is important if the new list is global and accessible |
227 | * to concurrent RCU readers. Note that RCU readers are not |
228 | * permitted to traverse the prev pointers without excluding |
229 | * this function. |
230 | */ |
231 | |
232 | last->next = next; |
233 | rcu_assign_pointer(list_next_rcu(prev), first); |
234 | first->prev = prev; |
235 | next->prev = last; |
236 | } |
237 | |
238 | /** |
239 | * list_splice_init_rcu - splice an RCU-protected list into an existing list, |
240 | * designed for stacks. |
241 | * @list: the RCU-protected list to splice |
242 | * @head: the place in the existing list to splice the first list into |
243 | * @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
244 | */ |
245 | static inline void list_splice_init_rcu(struct list_head *list, |
246 | struct list_head *head, |
247 | void (*sync)(void)) |
248 | { |
249 | if (!list_empty(list)) |
250 | __list_splice_init_rcu(list, head, head->next, sync); |
251 | } |
252 | |
253 | /** |
254 | * list_splice_tail_init_rcu - splice an RCU-protected list into an existing |
255 | * list, designed for queues. |
256 | * @list: the RCU-protected list to splice |
257 | * @head: the place in the existing list to splice the first list into |
258 | * @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
259 | */ |
260 | static inline void list_splice_tail_init_rcu(struct list_head *list, |
261 | struct list_head *head, |
262 | void (*sync)(void)) |
263 | { |
264 | if (!list_empty(list)) |
265 | __list_splice_init_rcu(list, head->prev, head, sync); |
266 | } |
267 | |
268 | /** |
269 | * list_entry_rcu - get the struct for this entry |
270 | * @ptr: the &struct list_head pointer. |
271 | * @type: the type of the struct this is embedded in. |
272 | * @member: the name of the list_head within the struct. |
273 | * |
274 | * This primitive may safely run concurrently with the _rcu list-mutation |
275 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). |
276 | */ |
277 | #define list_entry_rcu(ptr, type, member) \ |
278 | container_of(READ_ONCE(ptr), type, member) |
279 | |
280 | /* |
281 | * Where are list_empty_rcu() and list_first_entry_rcu()? |
282 | * |
283 | * Implementing those functions following their counterparts list_empty() and |
284 | * list_first_entry() is not advisable because they lead to subtle race |
285 | * conditions as the following snippet shows: |
286 | * |
287 | * if (!list_empty_rcu(mylist)) { |
288 | * struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member); |
289 | * do_something(bar); |
290 | * } |
291 | * |
292 | * The list may not be empty when list_empty_rcu checks it, but it may be when |
293 | * list_first_entry_rcu rereads the ->next pointer. |
294 | * |
295 | * Rereading the ->next pointer is not a problem for list_empty() and |
296 | * list_first_entry() because they would be protected by a lock that blocks |
297 | * writers. |
298 | * |
299 | * See list_first_or_null_rcu for an alternative. |
300 | */ |
301 | |
302 | /** |
303 | * list_first_or_null_rcu - get the first element from a list |
304 | * @ptr: the list head to take the element from. |
305 | * @type: the type of the struct this is embedded in. |
306 | * @member: the name of the list_head within the struct. |
307 | * |
308 | * Note that if the list is empty, it returns NULL. |
309 | * |
310 | * This primitive may safely run concurrently with the _rcu list-mutation |
311 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). |
312 | */ |
313 | #define list_first_or_null_rcu(ptr, type, member) \ |
314 | ({ \ |
315 | struct list_head *__ptr = (ptr); \ |
316 | struct list_head *__next = READ_ONCE(__ptr->next); \ |
317 | likely(__ptr != __next) ? list_entry_rcu(__next, type, member) : NULL; \ |
318 | }) |
319 | |
320 | /** |
321 | * list_next_or_null_rcu - get the first element from a list |
322 | * @head: the head for the list. |
323 | * @ptr: the list head to take the next element from. |
324 | * @type: the type of the struct this is embedded in. |
325 | * @member: the name of the list_head within the struct. |
326 | * |
327 | * Note that if the ptr is at the end of the list, NULL is returned. |
328 | * |
329 | * This primitive may safely run concurrently with the _rcu list-mutation |
330 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). |
331 | */ |
332 | #define list_next_or_null_rcu(head, ptr, type, member) \ |
333 | ({ \ |
334 | struct list_head *__head = (head); \ |
335 | struct list_head *__ptr = (ptr); \ |
336 | struct list_head *__next = READ_ONCE(__ptr->next); \ |
337 | likely(__next != __head) ? list_entry_rcu(__next, type, \ |
338 | member) : NULL; \ |
339 | }) |
340 | |
341 | /** |
342 | * list_for_each_entry_rcu - iterate over rcu list of given type |
343 | * @pos: the type * to use as a loop cursor. |
344 | * @head: the head for your list. |
345 | * @member: the name of the list_head within the struct. |
346 | * |
347 | * This list-traversal primitive may safely run concurrently with |
348 | * the _rcu list-mutation primitives such as list_add_rcu() |
349 | * as long as the traversal is guarded by rcu_read_lock(). |
350 | */ |
351 | #define list_for_each_entry_rcu(pos, head, member) \ |
352 | for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \ |
353 | &pos->member != (head); \ |
354 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
355 | |
356 | /** |
357 | * list_entry_lockless - get the struct for this entry |
358 | * @ptr: the &struct list_head pointer. |
359 | * @type: the type of the struct this is embedded in. |
360 | * @member: the name of the list_head within the struct. |
361 | * |
362 | * This primitive may safely run concurrently with the _rcu |
363 | * list-mutation primitives such as list_add_rcu(), but requires some |
364 | * implicit RCU read-side guarding. One example is running within a special |
365 | * exception-time environment where preemption is disabled and where lockdep |
366 | * cannot be invoked. Another example is when items are added to the list, |
367 | * but never deleted. |
368 | */ |
369 | #define list_entry_lockless(ptr, type, member) \ |
370 | container_of((typeof(ptr))READ_ONCE(ptr), type, member) |
371 | |
372 | /** |
373 | * list_for_each_entry_lockless - iterate over rcu list of given type |
374 | * @pos: the type * to use as a loop cursor. |
375 | * @head: the head for your list. |
376 | * @member: the name of the list_struct within the struct. |
377 | * |
378 | * This primitive may safely run concurrently with the _rcu |
379 | * list-mutation primitives such as list_add_rcu(), but requires some |
380 | * implicit RCU read-side guarding. One example is running within a special |
381 | * exception-time environment where preemption is disabled and where lockdep |
382 | * cannot be invoked. Another example is when items are added to the list, |
383 | * but never deleted. |
384 | */ |
385 | #define list_for_each_entry_lockless(pos, head, member) \ |
386 | for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \ |
387 | &pos->member != (head); \ |
388 | pos = list_entry_lockless(pos->member.next, typeof(*pos), member)) |
389 | |
390 | /** |
391 | * list_for_each_entry_continue_rcu - continue iteration over list of given type |
392 | * @pos: the type * to use as a loop cursor. |
393 | * @head: the head for your list. |
394 | * @member: the name of the list_head within the struct. |
395 | * |
396 | * Continue to iterate over list of given type, continuing after |
397 | * the current position which must have been in the list when the RCU read |
398 | * lock was taken. |
399 | * This would typically require either that you obtained the node from a |
400 | * previous walk of the list in the same RCU read-side critical section, or |
401 | * that you held some sort of non-RCU reference (such as a reference count) |
402 | * to keep the node alive *and* in the list. |
403 | * |
404 | * This iterator is similar to list_for_each_entry_from_rcu() except |
405 | * this starts after the given position and that one starts at the given |
406 | * position. |
407 | */ |
408 | #define list_for_each_entry_continue_rcu(pos, head, member) \ |
409 | for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \ |
410 | &pos->member != (head); \ |
411 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
412 | |
413 | /** |
414 | * list_for_each_entry_from_rcu - iterate over a list from current point |
415 | * @pos: the type * to use as a loop cursor. |
416 | * @head: the head for your list. |
417 | * @member: the name of the list_node within the struct. |
418 | * |
419 | * Iterate over the tail of a list starting from a given position, |
420 | * which must have been in the list when the RCU read lock was taken. |
421 | * This would typically require either that you obtained the node from a |
422 | * previous walk of the list in the same RCU read-side critical section, or |
423 | * that you held some sort of non-RCU reference (such as a reference count) |
424 | * to keep the node alive *and* in the list. |
425 | * |
426 | * This iterator is similar to list_for_each_entry_continue_rcu() except |
427 | * this starts from the given position and that one starts from the position |
428 | * after the given position. |
429 | */ |
430 | #define list_for_each_entry_from_rcu(pos, head, member) \ |
431 | for (; &(pos)->member != (head); \ |
432 | pos = list_entry_rcu(pos->member.next, typeof(*(pos)), member)) |
433 | |
434 | /** |
435 | * hlist_del_rcu - deletes entry from hash list without re-initialization |
436 | * @n: the element to delete from the hash list. |
437 | * |
438 | * Note: list_unhashed() on entry does not return true after this, |
439 | * the entry is in an undefined state. It is useful for RCU based |
440 | * lockfree traversal. |
441 | * |
442 | * In particular, it means that we can not poison the forward |
443 | * pointers that may still be used for walking the hash list. |
444 | * |
445 | * The caller must take whatever precautions are necessary |
446 | * (such as holding appropriate locks) to avoid racing |
447 | * with another list-mutation primitive, such as hlist_add_head_rcu() |
448 | * or hlist_del_rcu(), running on this same list. |
449 | * However, it is perfectly legal to run concurrently with |
450 | * the _rcu list-traversal primitives, such as |
451 | * hlist_for_each_entry(). |
452 | */ |
453 | static inline void hlist_del_rcu(struct hlist_node *n) |
454 | { |
455 | __hlist_del(n); |
456 | n->pprev = LIST_POISON2; |
457 | } |
458 | |
459 | /** |
460 | * hlist_replace_rcu - replace old entry by new one |
461 | * @old : the element to be replaced |
462 | * @new : the new element to insert |
463 | * |
464 | * The @old entry will be replaced with the @new entry atomically. |
465 | */ |
466 | static inline void hlist_replace_rcu(struct hlist_node *old, |
467 | struct hlist_node *new) |
468 | { |
469 | struct hlist_node *next = old->next; |
470 | |
471 | new->next = next; |
472 | new->pprev = old->pprev; |
473 | rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new); |
474 | if (next) |
475 | new->next->pprev = &new->next; |
476 | old->pprev = LIST_POISON2; |
477 | } |
478 | |
479 | /* |
480 | * return the first or the next element in an RCU protected hlist |
481 | */ |
482 | #define hlist_first_rcu(head) (*((struct hlist_node __rcu **)(&(head)->first))) |
483 | #define hlist_next_rcu(node) (*((struct hlist_node __rcu **)(&(node)->next))) |
484 | #define hlist_pprev_rcu(node) (*((struct hlist_node __rcu **)((node)->pprev))) |
485 | |
486 | /** |
487 | * hlist_add_head_rcu |
488 | * @n: the element to add to the hash list. |
489 | * @h: the list to add to. |
490 | * |
491 | * Description: |
492 | * Adds the specified element to the specified hlist, |
493 | * while permitting racing traversals. |
494 | * |
495 | * The caller must take whatever precautions are necessary |
496 | * (such as holding appropriate locks) to avoid racing |
497 | * with another list-mutation primitive, such as hlist_add_head_rcu() |
498 | * or hlist_del_rcu(), running on this same list. |
499 | * However, it is perfectly legal to run concurrently with |
500 | * the _rcu list-traversal primitives, such as |
501 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency |
502 | * problems on Alpha CPUs. Regardless of the type of CPU, the |
503 | * list-traversal primitive must be guarded by rcu_read_lock(). |
504 | */ |
505 | static inline void hlist_add_head_rcu(struct hlist_node *n, |
506 | struct hlist_head *h) |
507 | { |
508 | struct hlist_node *first = h->first; |
509 | |
510 | n->next = first; |
511 | n->pprev = &h->first; |
512 | rcu_assign_pointer(hlist_first_rcu(h), n); |
513 | if (first) |
514 | first->pprev = &n->next; |
515 | } |
516 | |
517 | /** |
518 | * hlist_add_tail_rcu |
519 | * @n: the element to add to the hash list. |
520 | * @h: the list to add to. |
521 | * |
522 | * Description: |
523 | * Adds the specified element to the specified hlist, |
524 | * while permitting racing traversals. |
525 | * |
526 | * The caller must take whatever precautions are necessary |
527 | * (such as holding appropriate locks) to avoid racing |
528 | * with another list-mutation primitive, such as hlist_add_head_rcu() |
529 | * or hlist_del_rcu(), running on this same list. |
530 | * However, it is perfectly legal to run concurrently with |
531 | * the _rcu list-traversal primitives, such as |
532 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency |
533 | * problems on Alpha CPUs. Regardless of the type of CPU, the |
534 | * list-traversal primitive must be guarded by rcu_read_lock(). |
535 | */ |
536 | static inline void hlist_add_tail_rcu(struct hlist_node *n, |
537 | struct hlist_head *h) |
538 | { |
539 | struct hlist_node *i, *last = NULL; |
540 | |
541 | /* Note: write side code, so rcu accessors are not needed. */ |
542 | for (i = h->first; i; i = i->next) |
543 | last = i; |
544 | |
545 | if (last) { |
546 | n->next = last->next; |
547 | n->pprev = &last->next; |
548 | rcu_assign_pointer(hlist_next_rcu(last), n); |
549 | } else { |
550 | hlist_add_head_rcu(n, h); |
551 | } |
552 | } |
553 | |
554 | /** |
555 | * hlist_add_before_rcu |
556 | * @n: the new element to add to the hash list. |
557 | * @next: the existing element to add the new element before. |
558 | * |
559 | * Description: |
560 | * Adds the specified element to the specified hlist |
561 | * before the specified node while permitting racing traversals. |
562 | * |
563 | * The caller must take whatever precautions are necessary |
564 | * (such as holding appropriate locks) to avoid racing |
565 | * with another list-mutation primitive, such as hlist_add_head_rcu() |
566 | * or hlist_del_rcu(), running on this same list. |
567 | * However, it is perfectly legal to run concurrently with |
568 | * the _rcu list-traversal primitives, such as |
569 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency |
570 | * problems on Alpha CPUs. |
571 | */ |
572 | static inline void hlist_add_before_rcu(struct hlist_node *n, |
573 | struct hlist_node *next) |
574 | { |
575 | n->pprev = next->pprev; |
576 | n->next = next; |
577 | rcu_assign_pointer(hlist_pprev_rcu(n), n); |
578 | next->pprev = &n->next; |
579 | } |
580 | |
581 | /** |
582 | * hlist_add_behind_rcu |
583 | * @n: the new element to add to the hash list. |
584 | * @prev: the existing element to add the new element after. |
585 | * |
586 | * Description: |
587 | * Adds the specified element to the specified hlist |
588 | * after the specified node while permitting racing traversals. |
589 | * |
590 | * The caller must take whatever precautions are necessary |
591 | * (such as holding appropriate locks) to avoid racing |
592 | * with another list-mutation primitive, such as hlist_add_head_rcu() |
593 | * or hlist_del_rcu(), running on this same list. |
594 | * However, it is perfectly legal to run concurrently with |
595 | * the _rcu list-traversal primitives, such as |
596 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency |
597 | * problems on Alpha CPUs. |
598 | */ |
599 | static inline void hlist_add_behind_rcu(struct hlist_node *n, |
600 | struct hlist_node *prev) |
601 | { |
602 | n->next = prev->next; |
603 | n->pprev = &prev->next; |
604 | rcu_assign_pointer(hlist_next_rcu(prev), n); |
605 | if (n->next) |
606 | n->next->pprev = &n->next; |
607 | } |
608 | |
609 | #define __hlist_for_each_rcu(pos, head) \ |
610 | for (pos = rcu_dereference(hlist_first_rcu(head)); \ |
611 | pos; \ |
612 | pos = rcu_dereference(hlist_next_rcu(pos))) |
613 | |
614 | /** |
615 | * hlist_for_each_entry_rcu - iterate over rcu list of given type |
616 | * @pos: the type * to use as a loop cursor. |
617 | * @head: the head for your list. |
618 | * @member: the name of the hlist_node within the struct. |
619 | * |
620 | * This list-traversal primitive may safely run concurrently with |
621 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() |
622 | * as long as the traversal is guarded by rcu_read_lock(). |
623 | */ |
624 | #define hlist_for_each_entry_rcu(pos, head, member) \ |
625 | for (pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\ |
626 | typeof(*(pos)), member); \ |
627 | pos; \ |
628 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\ |
629 | &(pos)->member)), typeof(*(pos)), member)) |
630 | |
631 | /** |
632 | * hlist_for_each_entry_rcu_notrace - iterate over rcu list of given type (for tracing) |
633 | * @pos: the type * to use as a loop cursor. |
634 | * @head: the head for your list. |
635 | * @member: the name of the hlist_node within the struct. |
636 | * |
637 | * This list-traversal primitive may safely run concurrently with |
638 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() |
639 | * as long as the traversal is guarded by rcu_read_lock(). |
640 | * |
641 | * This is the same as hlist_for_each_entry_rcu() except that it does |
642 | * not do any RCU debugging or tracing. |
643 | */ |
644 | #define hlist_for_each_entry_rcu_notrace(pos, head, member) \ |
645 | for (pos = hlist_entry_safe (rcu_dereference_raw_notrace(hlist_first_rcu(head)),\ |
646 | typeof(*(pos)), member); \ |
647 | pos; \ |
648 | pos = hlist_entry_safe(rcu_dereference_raw_notrace(hlist_next_rcu(\ |
649 | &(pos)->member)), typeof(*(pos)), member)) |
650 | |
651 | /** |
652 | * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type |
653 | * @pos: the type * to use as a loop cursor. |
654 | * @head: the head for your list. |
655 | * @member: the name of the hlist_node within the struct. |
656 | * |
657 | * This list-traversal primitive may safely run concurrently with |
658 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() |
659 | * as long as the traversal is guarded by rcu_read_lock(). |
660 | */ |
661 | #define hlist_for_each_entry_rcu_bh(pos, head, member) \ |
662 | for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_first_rcu(head)),\ |
663 | typeof(*(pos)), member); \ |
664 | pos; \ |
665 | pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(\ |
666 | &(pos)->member)), typeof(*(pos)), member)) |
667 | |
668 | /** |
669 | * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point |
670 | * @pos: the type * to use as a loop cursor. |
671 | * @member: the name of the hlist_node within the struct. |
672 | */ |
673 | #define hlist_for_each_entry_continue_rcu(pos, member) \ |
674 | for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
675 | &(pos)->member)), typeof(*(pos)), member); \ |
676 | pos; \ |
677 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
678 | &(pos)->member)), typeof(*(pos)), member)) |
679 | |
680 | /** |
681 | * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point |
682 | * @pos: the type * to use as a loop cursor. |
683 | * @member: the name of the hlist_node within the struct. |
684 | */ |
685 | #define hlist_for_each_entry_continue_rcu_bh(pos, member) \ |
686 | for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \ |
687 | &(pos)->member)), typeof(*(pos)), member); \ |
688 | pos; \ |
689 | pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \ |
690 | &(pos)->member)), typeof(*(pos)), member)) |
691 | |
692 | /** |
693 | * hlist_for_each_entry_from_rcu - iterate over a hlist continuing from current point |
694 | * @pos: the type * to use as a loop cursor. |
695 | * @member: the name of the hlist_node within the struct. |
696 | */ |
697 | #define hlist_for_each_entry_from_rcu(pos, member) \ |
698 | for (; pos; \ |
699 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
700 | &(pos)->member)), typeof(*(pos)), member)) |
701 | |
702 | #endif /* __KERNEL__ */ |
703 | #endif |
704 | |