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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 : 3 : 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 : : * Check during list traversal that we are within an RCU reader
45 : : */
46 : :
47 : : #define check_arg_count_one(dummy)
48 : :
49 : : #ifdef CONFIG_PROVE_RCU_LIST
50 : : #define __list_check_rcu(dummy, cond, extra...) \
51 : : ({ \
52 : : check_arg_count_one(extra); \
53 : : RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(), \
54 : : "RCU-list traversed in non-reader section!"); \
55 : : })
56 : : #else
57 : : #define __list_check_rcu(dummy, cond, extra...) \
58 : : ({ check_arg_count_one(extra); })
59 : : #endif
60 : :
61 : : /*
62 : : * Insert a new entry between two known consecutive entries.
63 : : *
64 : : * This is only for internal list manipulation where we know
65 : : * the prev/next entries already!
66 : : */
67 : : static inline void __list_add_rcu(struct list_head *new,
68 : : struct list_head *prev, struct list_head *next)
69 : : {
70 : : if (!__list_add_valid(new, prev, next))
71 : : return;
72 : :
73 : 3 : new->next = next;
74 : 3 : new->prev = prev;
75 : 3 : rcu_assign_pointer(list_next_rcu(prev), new);
76 : 3 : next->prev = new;
77 : : }
78 : :
79 : : /**
80 : : * list_add_rcu - add a new entry to rcu-protected list
81 : : * @new: new entry to be added
82 : : * @head: list head to add it after
83 : : *
84 : : * Insert a new entry after the specified head.
85 : : * This is good for implementing stacks.
86 : : *
87 : : * The caller must take whatever precautions are necessary
88 : : * (such as holding appropriate locks) to avoid racing
89 : : * with another list-mutation primitive, such as list_add_rcu()
90 : : * or list_del_rcu(), running on this same list.
91 : : * However, it is perfectly legal to run concurrently with
92 : : * the _rcu list-traversal primitives, such as
93 : : * list_for_each_entry_rcu().
94 : : */
95 : : static inline void list_add_rcu(struct list_head *new, struct list_head *head)
96 : : {
97 : 3 : __list_add_rcu(new, head, head->next);
98 : : }
99 : :
100 : : /**
101 : : * list_add_tail_rcu - add a new entry to rcu-protected list
102 : : * @new: new entry to be added
103 : : * @head: list head to add it before
104 : : *
105 : : * Insert a new entry before the specified head.
106 : : * This is useful for implementing queues.
107 : : *
108 : : * The caller must take whatever precautions are necessary
109 : : * (such as holding appropriate locks) to avoid racing
110 : : * with another list-mutation primitive, such as list_add_tail_rcu()
111 : : * or list_del_rcu(), running on this same list.
112 : : * However, it is perfectly legal to run concurrently with
113 : : * the _rcu list-traversal primitives, such as
114 : : * list_for_each_entry_rcu().
115 : : */
116 : : static inline void list_add_tail_rcu(struct list_head *new,
117 : : struct list_head *head)
118 : : {
119 : 3 : __list_add_rcu(new, head->prev, head);
120 : : }
121 : :
122 : : /**
123 : : * list_del_rcu - deletes entry from list without re-initialization
124 : : * @entry: the element to delete from the list.
125 : : *
126 : : * Note: list_empty() on entry does not return true after this,
127 : : * the entry is in an undefined state. It is useful for RCU based
128 : : * lockfree traversal.
129 : : *
130 : : * In particular, it means that we can not poison the forward
131 : : * pointers that may still be used for walking the list.
132 : : *
133 : : * The caller must take whatever precautions are necessary
134 : : * (such as holding appropriate locks) to avoid racing
135 : : * with another list-mutation primitive, such as list_del_rcu()
136 : : * or list_add_rcu(), running on this same list.
137 : : * However, it is perfectly legal to run concurrently with
138 : : * the _rcu list-traversal primitives, such as
139 : : * list_for_each_entry_rcu().
140 : : *
141 : : * Note that the caller is not permitted to immediately free
142 : : * the newly deleted entry. Instead, either synchronize_rcu()
143 : : * or call_rcu() must be used to defer freeing until an RCU
144 : : * grace period has elapsed.
145 : : */
146 : : static inline void list_del_rcu(struct list_head *entry)
147 : : {
148 : : __list_del_entry(entry);
149 : 3 : entry->prev = LIST_POISON2;
150 : : }
151 : :
152 : : /**
153 : : * hlist_del_init_rcu - deletes entry from hash list with re-initialization
154 : : * @n: the element to delete from the hash list.
155 : : *
156 : : * Note: list_unhashed() on the node return true after this. It is
157 : : * useful for RCU based read lockfree traversal if the writer side
158 : : * must know if the list entry is still hashed or already unhashed.
159 : : *
160 : : * In particular, it means that we can not poison the forward pointers
161 : : * that may still be used for walking the hash list and we can only
162 : : * zero the pprev pointer so list_unhashed() will return true after
163 : : * this.
164 : : *
165 : : * The caller must take whatever precautions are necessary (such as
166 : : * holding appropriate locks) to avoid racing with another
167 : : * list-mutation primitive, such as hlist_add_head_rcu() or
168 : : * hlist_del_rcu(), running on this same list. However, it is
169 : : * perfectly legal to run concurrently with the _rcu list-traversal
170 : : * primitives, such as hlist_for_each_entry_rcu().
171 : : */
172 : : static inline void hlist_del_init_rcu(struct hlist_node *n)
173 : : {
174 : 3 : if (!hlist_unhashed(n)) {
175 : : __hlist_del(n);
176 : 3 : n->pprev = NULL;
177 : : }
178 : : }
179 : :
180 : : /**
181 : : * list_replace_rcu - replace old entry by new one
182 : : * @old : the element to be replaced
183 : : * @new : the new element to insert
184 : : *
185 : : * The @old entry will be replaced with the @new entry atomically.
186 : : * Note: @old should not be empty.
187 : : */
188 : : static inline void list_replace_rcu(struct list_head *old,
189 : : struct list_head *new)
190 : : {
191 : 0 : new->next = old->next;
192 : 0 : new->prev = old->prev;
193 : 0 : rcu_assign_pointer(list_next_rcu(new->prev), new);
194 : 0 : new->next->prev = new;
195 : 0 : old->prev = LIST_POISON2;
196 : : }
197 : :
198 : : /**
199 : : * __list_splice_init_rcu - join an RCU-protected list into an existing list.
200 : : * @list: the RCU-protected list to splice
201 : : * @prev: points to the last element of the existing list
202 : : * @next: points to the first element of the existing list
203 : : * @sync: synchronize_rcu, synchronize_rcu_expedited, ...
204 : : *
205 : : * The list pointed to by @prev and @next can be RCU-read traversed
206 : : * concurrently with this function.
207 : : *
208 : : * Note that this function blocks.
209 : : *
210 : : * Important note: the caller must take whatever action is necessary to prevent
211 : : * any other updates to the existing list. In principle, it is possible to
212 : : * modify the list as soon as sync() begins execution. If this sort of thing
213 : : * becomes necessary, an alternative version based on call_rcu() could be
214 : : * created. But only if -really- needed -- there is no shortage of RCU API
215 : : * members.
216 : : */
217 : : static inline void __list_splice_init_rcu(struct list_head *list,
218 : : struct list_head *prev,
219 : : struct list_head *next,
220 : : void (*sync)(void))
221 : : {
222 : 0 : struct list_head *first = list->next;
223 : 0 : struct list_head *last = list->prev;
224 : :
225 : : /*
226 : : * "first" and "last" tracking list, so initialize it. RCU readers
227 : : * have access to this list, so we must use INIT_LIST_HEAD_RCU()
228 : : * instead of INIT_LIST_HEAD().
229 : : */
230 : :
231 : : INIT_LIST_HEAD_RCU(list);
232 : :
233 : : /*
234 : : * At this point, the list body still points to the source list.
235 : : * Wait for any readers to finish using the list before splicing
236 : : * the list body into the new list. Any new readers will see
237 : : * an empty list.
238 : : */
239 : :
240 : 0 : sync();
241 : :
242 : : /*
243 : : * Readers are finished with the source list, so perform splice.
244 : : * The order is important if the new list is global and accessible
245 : : * to concurrent RCU readers. Note that RCU readers are not
246 : : * permitted to traverse the prev pointers without excluding
247 : : * this function.
248 : : */
249 : :
250 : 0 : last->next = next;
251 : 0 : rcu_assign_pointer(list_next_rcu(prev), first);
252 : 0 : first->prev = prev;
253 : 0 : next->prev = last;
254 : : }
255 : :
256 : : /**
257 : : * list_splice_init_rcu - splice an RCU-protected list into an existing list,
258 : : * designed for stacks.
259 : : * @list: the RCU-protected list to splice
260 : : * @head: the place in the existing list to splice the first list into
261 : : * @sync: synchronize_rcu, synchronize_rcu_expedited, ...
262 : : */
263 : : static inline void list_splice_init_rcu(struct list_head *list,
264 : : struct list_head *head,
265 : : void (*sync)(void))
266 : : {
267 : 0 : if (!list_empty(list))
268 : : __list_splice_init_rcu(list, head, head->next, sync);
269 : : }
270 : :
271 : : /**
272 : : * list_splice_tail_init_rcu - splice an RCU-protected list into an existing
273 : : * list, designed for queues.
274 : : * @list: the RCU-protected list to splice
275 : : * @head: the place in the existing list to splice the first list into
276 : : * @sync: synchronize_rcu, synchronize_rcu_expedited, ...
277 : : */
278 : : static inline void list_splice_tail_init_rcu(struct list_head *list,
279 : : struct list_head *head,
280 : : void (*sync)(void))
281 : : {
282 : : if (!list_empty(list))
283 : : __list_splice_init_rcu(list, head->prev, head, sync);
284 : : }
285 : :
286 : : /**
287 : : * list_entry_rcu - get the struct for this entry
288 : : * @ptr: the &struct list_head pointer.
289 : : * @type: the type of the struct this is embedded in.
290 : : * @member: the name of the list_head within the struct.
291 : : *
292 : : * This primitive may safely run concurrently with the _rcu list-mutation
293 : : * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
294 : : */
295 : : #define list_entry_rcu(ptr, type, member) \
296 : : container_of(READ_ONCE(ptr), type, member)
297 : :
298 : : /*
299 : : * Where are list_empty_rcu() and list_first_entry_rcu()?
300 : : *
301 : : * Implementing those functions following their counterparts list_empty() and
302 : : * list_first_entry() is not advisable because they lead to subtle race
303 : : * conditions as the following snippet shows:
304 : : *
305 : : * if (!list_empty_rcu(mylist)) {
306 : : * struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member);
307 : : * do_something(bar);
308 : : * }
309 : : *
310 : : * The list may not be empty when list_empty_rcu checks it, but it may be when
311 : : * list_first_entry_rcu rereads the ->next pointer.
312 : : *
313 : : * Rereading the ->next pointer is not a problem for list_empty() and
314 : : * list_first_entry() because they would be protected by a lock that blocks
315 : : * writers.
316 : : *
317 : : * See list_first_or_null_rcu for an alternative.
318 : : */
319 : :
320 : : /**
321 : : * list_first_or_null_rcu - get the first element from a list
322 : : * @ptr: the list head to take the element from.
323 : : * @type: the type of the struct this is embedded in.
324 : : * @member: the name of the list_head within the struct.
325 : : *
326 : : * Note that if the list is empty, it returns NULL.
327 : : *
328 : : * This primitive may safely run concurrently with the _rcu list-mutation
329 : : * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
330 : : */
331 : : #define list_first_or_null_rcu(ptr, type, member) \
332 : : ({ \
333 : : struct list_head *__ptr = (ptr); \
334 : : struct list_head *__next = READ_ONCE(__ptr->next); \
335 : : likely(__ptr != __next) ? list_entry_rcu(__next, type, member) : NULL; \
336 : : })
337 : :
338 : : /**
339 : : * list_next_or_null_rcu - get the first element from a list
340 : : * @head: the head for the list.
341 : : * @ptr: the list head to take the next element from.
342 : : * @type: the type of the struct this is embedded in.
343 : : * @member: the name of the list_head within the struct.
344 : : *
345 : : * Note that if the ptr is at the end of the list, NULL is returned.
346 : : *
347 : : * This primitive may safely run concurrently with the _rcu list-mutation
348 : : * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
349 : : */
350 : : #define list_next_or_null_rcu(head, ptr, type, member) \
351 : : ({ \
352 : : struct list_head *__head = (head); \
353 : : struct list_head *__ptr = (ptr); \
354 : : struct list_head *__next = READ_ONCE(__ptr->next); \
355 : : likely(__next != __head) ? list_entry_rcu(__next, type, \
356 : : member) : NULL; \
357 : : })
358 : :
359 : : /**
360 : : * list_for_each_entry_rcu - iterate over rcu list of given type
361 : : * @pos: the type * to use as a loop cursor.
362 : : * @head: the head for your list.
363 : : * @member: the name of the list_head within the struct.
364 : : * @cond: optional lockdep expression if called from non-RCU protection.
365 : : *
366 : : * This list-traversal primitive may safely run concurrently with
367 : : * the _rcu list-mutation primitives such as list_add_rcu()
368 : : * as long as the traversal is guarded by rcu_read_lock().
369 : : */
370 : : #define list_for_each_entry_rcu(pos, head, member, cond...) \
371 : : for (__list_check_rcu(dummy, ## cond, 0), \
372 : : pos = list_entry_rcu((head)->next, typeof(*pos), member); \
373 : : &pos->member != (head); \
374 : : pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
375 : :
376 : : /**
377 : : * list_entry_lockless - get the struct for this entry
378 : : * @ptr: the &struct list_head pointer.
379 : : * @type: the type of the struct this is embedded in.
380 : : * @member: the name of the list_head within the struct.
381 : : *
382 : : * This primitive may safely run concurrently with the _rcu
383 : : * list-mutation primitives such as list_add_rcu(), but requires some
384 : : * implicit RCU read-side guarding. One example is running within a special
385 : : * exception-time environment where preemption is disabled and where lockdep
386 : : * cannot be invoked. Another example is when items are added to the list,
387 : : * but never deleted.
388 : : */
389 : : #define list_entry_lockless(ptr, type, member) \
390 : : container_of((typeof(ptr))READ_ONCE(ptr), type, member)
391 : :
392 : : /**
393 : : * list_for_each_entry_lockless - iterate over rcu list of given type
394 : : * @pos: the type * to use as a loop cursor.
395 : : * @head: the head for your list.
396 : : * @member: the name of the list_struct within the struct.
397 : : *
398 : : * This primitive may safely run concurrently with the _rcu
399 : : * list-mutation primitives such as list_add_rcu(), but requires some
400 : : * implicit RCU read-side guarding. One example is running within a special
401 : : * exception-time environment where preemption is disabled and where lockdep
402 : : * cannot be invoked. Another example is when items are added to the list,
403 : : * but never deleted.
404 : : */
405 : : #define list_for_each_entry_lockless(pos, head, member) \
406 : : for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \
407 : : &pos->member != (head); \
408 : : pos = list_entry_lockless(pos->member.next, typeof(*pos), member))
409 : :
410 : : /**
411 : : * list_for_each_entry_continue_rcu - continue iteration over list of given type
412 : : * @pos: the type * to use as a loop cursor.
413 : : * @head: the head for your list.
414 : : * @member: the name of the list_head within the struct.
415 : : *
416 : : * Continue to iterate over list of given type, continuing after
417 : : * the current position which must have been in the list when the RCU read
418 : : * lock was taken.
419 : : * This would typically require either that you obtained the node from a
420 : : * previous walk of the list in the same RCU read-side critical section, or
421 : : * that you held some sort of non-RCU reference (such as a reference count)
422 : : * to keep the node alive *and* in the list.
423 : : *
424 : : * This iterator is similar to list_for_each_entry_from_rcu() except
425 : : * this starts after the given position and that one starts at the given
426 : : * position.
427 : : */
428 : : #define list_for_each_entry_continue_rcu(pos, head, member) \
429 : : for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \
430 : : &pos->member != (head); \
431 : : pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
432 : :
433 : : /**
434 : : * list_for_each_entry_from_rcu - iterate over a list from current point
435 : : * @pos: the type * to use as a loop cursor.
436 : : * @head: the head for your list.
437 : : * @member: the name of the list_node within the struct.
438 : : *
439 : : * Iterate over the tail of a list starting from a given position,
440 : : * which must have been in the list when the RCU read lock was taken.
441 : : * This would typically require either that you obtained the node from a
442 : : * previous walk of the list in the same RCU read-side critical section, or
443 : : * that you held some sort of non-RCU reference (such as a reference count)
444 : : * to keep the node alive *and* in the list.
445 : : *
446 : : * This iterator is similar to list_for_each_entry_continue_rcu() except
447 : : * this starts from the given position and that one starts from the position
448 : : * after the given position.
449 : : */
450 : : #define list_for_each_entry_from_rcu(pos, head, member) \
451 : : for (; &(pos)->member != (head); \
452 : : pos = list_entry_rcu(pos->member.next, typeof(*(pos)), member))
453 : :
454 : : /**
455 : : * hlist_del_rcu - deletes entry from hash list without re-initialization
456 : : * @n: the element to delete from the hash list.
457 : : *
458 : : * Note: list_unhashed() on entry does not return true after this,
459 : : * the entry is in an undefined state. It is useful for RCU based
460 : : * lockfree traversal.
461 : : *
462 : : * In particular, it means that we can not poison the forward
463 : : * pointers that may still be used for walking the hash list.
464 : : *
465 : : * The caller must take whatever precautions are necessary
466 : : * (such as holding appropriate locks) to avoid racing
467 : : * with another list-mutation primitive, such as hlist_add_head_rcu()
468 : : * or hlist_del_rcu(), running on this same list.
469 : : * However, it is perfectly legal to run concurrently with
470 : : * the _rcu list-traversal primitives, such as
471 : : * hlist_for_each_entry().
472 : : */
473 : : static inline void hlist_del_rcu(struct hlist_node *n)
474 : : {
475 : : __hlist_del(n);
476 : 3 : n->pprev = LIST_POISON2;
477 : : }
478 : :
479 : : /**
480 : : * hlist_replace_rcu - replace old entry by new one
481 : : * @old : the element to be replaced
482 : : * @new : the new element to insert
483 : : *
484 : : * The @old entry will be replaced with the @new entry atomically.
485 : : */
486 : : static inline void hlist_replace_rcu(struct hlist_node *old,
487 : : struct hlist_node *new)
488 : : {
489 : 0 : struct hlist_node *next = old->next;
490 : :
491 : 0 : new->next = next;
492 : 0 : new->pprev = old->pprev;
493 : 0 : rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new);
494 : 0 : if (next)
495 : 0 : new->next->pprev = &new->next;
496 : 0 : old->pprev = LIST_POISON2;
497 : : }
498 : :
499 : : /*
500 : : * return the first or the next element in an RCU protected hlist
501 : : */
502 : : #define hlist_first_rcu(head) (*((struct hlist_node __rcu **)(&(head)->first)))
503 : : #define hlist_next_rcu(node) (*((struct hlist_node __rcu **)(&(node)->next)))
504 : : #define hlist_pprev_rcu(node) (*((struct hlist_node __rcu **)((node)->pprev)))
505 : :
506 : : /**
507 : : * hlist_add_head_rcu
508 : : * @n: the element to add to the hash list.
509 : : * @h: the list to add to.
510 : : *
511 : : * Description:
512 : : * Adds the specified element to the specified hlist,
513 : : * while permitting racing traversals.
514 : : *
515 : : * The caller must take whatever precautions are necessary
516 : : * (such as holding appropriate locks) to avoid racing
517 : : * with another list-mutation primitive, such as hlist_add_head_rcu()
518 : : * or hlist_del_rcu(), running on this same list.
519 : : * However, it is perfectly legal to run concurrently with
520 : : * the _rcu list-traversal primitives, such as
521 : : * hlist_for_each_entry_rcu(), used to prevent memory-consistency
522 : : * problems on Alpha CPUs. Regardless of the type of CPU, the
523 : : * list-traversal primitive must be guarded by rcu_read_lock().
524 : : */
525 : : static inline void hlist_add_head_rcu(struct hlist_node *n,
526 : : struct hlist_head *h)
527 : : {
528 : 3 : struct hlist_node *first = h->first;
529 : :
530 : 3 : n->next = first;
531 : 3 : n->pprev = &h->first;
532 : 3 : rcu_assign_pointer(hlist_first_rcu(h), n);
533 : 3 : if (first)
534 : 3 : first->pprev = &n->next;
535 : : }
536 : :
537 : : /**
538 : : * hlist_add_tail_rcu
539 : : * @n: the element to add to the hash list.
540 : : * @h: the list to add to.
541 : : *
542 : : * Description:
543 : : * Adds the specified element to the specified hlist,
544 : : * while permitting racing traversals.
545 : : *
546 : : * The caller must take whatever precautions are necessary
547 : : * (such as holding appropriate locks) to avoid racing
548 : : * with another list-mutation primitive, such as hlist_add_head_rcu()
549 : : * or hlist_del_rcu(), running on this same list.
550 : : * However, it is perfectly legal to run concurrently with
551 : : * the _rcu list-traversal primitives, such as
552 : : * hlist_for_each_entry_rcu(), used to prevent memory-consistency
553 : : * problems on Alpha CPUs. Regardless of the type of CPU, the
554 : : * list-traversal primitive must be guarded by rcu_read_lock().
555 : : */
556 : 3 : static inline void hlist_add_tail_rcu(struct hlist_node *n,
557 : : struct hlist_head *h)
558 : : {
559 : : struct hlist_node *i, *last = NULL;
560 : :
561 : : /* Note: write side code, so rcu accessors are not needed. */
562 : 3 : for (i = h->first; i; i = i->next)
563 : : last = i;
564 : :
565 : 3 : if (last) {
566 : 3 : n->next = last->next;
567 : 3 : n->pprev = &last->next;
568 : 3 : rcu_assign_pointer(hlist_next_rcu(last), n);
569 : : } else {
570 : : hlist_add_head_rcu(n, h);
571 : : }
572 : 3 : }
573 : :
574 : : /**
575 : : * hlist_add_before_rcu
576 : : * @n: the new element to add to the hash list.
577 : : * @next: the existing element to add the new element before.
578 : : *
579 : : * Description:
580 : : * Adds the specified element to the specified hlist
581 : : * before the specified node while permitting racing traversals.
582 : : *
583 : : * The caller must take whatever precautions are necessary
584 : : * (such as holding appropriate locks) to avoid racing
585 : : * with another list-mutation primitive, such as hlist_add_head_rcu()
586 : : * or hlist_del_rcu(), running on this same list.
587 : : * However, it is perfectly legal to run concurrently with
588 : : * the _rcu list-traversal primitives, such as
589 : : * hlist_for_each_entry_rcu(), used to prevent memory-consistency
590 : : * problems on Alpha CPUs.
591 : : */
592 : : static inline void hlist_add_before_rcu(struct hlist_node *n,
593 : : struct hlist_node *next)
594 : : {
595 : 3 : n->pprev = next->pprev;
596 : 3 : n->next = next;
597 : 3 : rcu_assign_pointer(hlist_pprev_rcu(n), n);
598 : 3 : next->pprev = &n->next;
599 : : }
600 : :
601 : : /**
602 : : * hlist_add_behind_rcu
603 : : * @n: the new element to add to the hash list.
604 : : * @prev: the existing element to add the new element after.
605 : : *
606 : : * Description:
607 : : * Adds the specified element to the specified hlist
608 : : * after the specified node while permitting racing traversals.
609 : : *
610 : : * The caller must take whatever precautions are necessary
611 : : * (such as holding appropriate locks) to avoid racing
612 : : * with another list-mutation primitive, such as hlist_add_head_rcu()
613 : : * or hlist_del_rcu(), running on this same list.
614 : : * However, it is perfectly legal to run concurrently with
615 : : * the _rcu list-traversal primitives, such as
616 : : * hlist_for_each_entry_rcu(), used to prevent memory-consistency
617 : : * problems on Alpha CPUs.
618 : : */
619 : : static inline void hlist_add_behind_rcu(struct hlist_node *n,
620 : : struct hlist_node *prev)
621 : : {
622 : 3 : n->next = prev->next;
623 : 3 : n->pprev = &prev->next;
624 : 3 : rcu_assign_pointer(hlist_next_rcu(prev), n);
625 : 3 : if (n->next)
626 : 0 : n->next->pprev = &n->next;
627 : : }
628 : :
629 : : #define __hlist_for_each_rcu(pos, head) \
630 : : for (pos = rcu_dereference(hlist_first_rcu(head)); \
631 : : pos; \
632 : : pos = rcu_dereference(hlist_next_rcu(pos)))
633 : :
634 : : /**
635 : : * hlist_for_each_entry_rcu - iterate over rcu list of given type
636 : : * @pos: the type * to use as a loop cursor.
637 : : * @head: the head for your list.
638 : : * @member: the name of the hlist_node within the struct.
639 : : * @cond: optional lockdep expression if called from non-RCU protection.
640 : : *
641 : : * This list-traversal primitive may safely run concurrently with
642 : : * the _rcu list-mutation primitives such as hlist_add_head_rcu()
643 : : * as long as the traversal is guarded by rcu_read_lock().
644 : : */
645 : : #define hlist_for_each_entry_rcu(pos, head, member, cond...) \
646 : : for (__list_check_rcu(dummy, ## cond, 0), \
647 : : pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\
648 : : typeof(*(pos)), member); \
649 : : pos; \
650 : : pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\
651 : : &(pos)->member)), typeof(*(pos)), member))
652 : :
653 : : /**
654 : : * hlist_for_each_entry_rcu_notrace - iterate over rcu list of given type (for tracing)
655 : : * @pos: the type * to use as a loop cursor.
656 : : * @head: the head for your list.
657 : : * @member: the name of the hlist_node within the struct.
658 : : *
659 : : * This list-traversal primitive may safely run concurrently with
660 : : * the _rcu list-mutation primitives such as hlist_add_head_rcu()
661 : : * as long as the traversal is guarded by rcu_read_lock().
662 : : *
663 : : * This is the same as hlist_for_each_entry_rcu() except that it does
664 : : * not do any RCU debugging or tracing.
665 : : */
666 : : #define hlist_for_each_entry_rcu_notrace(pos, head, member) \
667 : : for (pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_first_rcu(head)),\
668 : : typeof(*(pos)), member); \
669 : : pos; \
670 : : pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_next_rcu(\
671 : : &(pos)->member)), typeof(*(pos)), member))
672 : :
673 : : /**
674 : : * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type
675 : : * @pos: the type * to use as a loop cursor.
676 : : * @head: the head for your list.
677 : : * @member: the name of the hlist_node within the struct.
678 : : *
679 : : * This list-traversal primitive may safely run concurrently with
680 : : * the _rcu list-mutation primitives such as hlist_add_head_rcu()
681 : : * as long as the traversal is guarded by rcu_read_lock().
682 : : */
683 : : #define hlist_for_each_entry_rcu_bh(pos, head, member) \
684 : : for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_first_rcu(head)),\
685 : : typeof(*(pos)), member); \
686 : : pos; \
687 : : pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(\
688 : : &(pos)->member)), typeof(*(pos)), member))
689 : :
690 : : /**
691 : : * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point
692 : : * @pos: the type * to use as a loop cursor.
693 : : * @member: the name of the hlist_node within the struct.
694 : : */
695 : : #define hlist_for_each_entry_continue_rcu(pos, member) \
696 : : for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
697 : : &(pos)->member)), typeof(*(pos)), member); \
698 : : pos; \
699 : : pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
700 : : &(pos)->member)), typeof(*(pos)), member))
701 : :
702 : : /**
703 : : * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point
704 : : * @pos: the type * to use as a loop cursor.
705 : : * @member: the name of the hlist_node within the struct.
706 : : */
707 : : #define hlist_for_each_entry_continue_rcu_bh(pos, member) \
708 : : for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \
709 : : &(pos)->member)), typeof(*(pos)), member); \
710 : : pos; \
711 : : pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \
712 : : &(pos)->member)), typeof(*(pos)), member))
713 : :
714 : : /**
715 : : * hlist_for_each_entry_from_rcu - iterate over a hlist continuing from current point
716 : : * @pos: the type * to use as a loop cursor.
717 : : * @member: the name of the hlist_node within the struct.
718 : : */
719 : : #define hlist_for_each_entry_from_rcu(pos, member) \
720 : : for (; pos; \
721 : : pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
722 : : &(pos)->member)), typeof(*(pos)), member))
723 : :
724 : : #endif /* __KERNEL__ */
725 : : #endif
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