Commit | Line | Data |
---|---|---|
b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
82524746 FBH |
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> | |
10aa9d2c | 11 | #include <linux/rcupdate.h> |
82524746 | 12 | |
65e6bf48 PM |
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 | ||
2a855b64 PM |
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 | { | |
7d0ae808 PM |
33 | WRITE_ONCE(list->next, list); |
34 | WRITE_ONCE(list->prev, list); | |
2a855b64 PM |
35 | } |
36 | ||
67bdbffd AB |
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 | ||
afa47fdf MB |
43 | /** |
44 | * list_tail_rcu - returns the prev pointer of the head of the list | |
45 | * @head: the head of the list | |
46 | * | |
47 | * Note: This should only be used with the list header, and even then | |
48 | * only if list_del() and similar primitives are not also used on the | |
49 | * list header. | |
50 | */ | |
51 | #define list_tail_rcu(head) (*((struct list_head __rcu **)(&(head)->prev))) | |
52 | ||
28875945 JFG |
53 | /* |
54 | * Check during list traversal that we are within an RCU reader | |
55 | */ | |
56 | ||
57 | #define check_arg_count_one(dummy) | |
58 | ||
59 | #ifdef CONFIG_PROVE_RCU_LIST | |
60 | #define __list_check_rcu(dummy, cond, extra...) \ | |
61 | ({ \ | |
62 | check_arg_count_one(extra); \ | |
4dfd5cd8 | 63 | RCU_LOCKDEP_WARN(!(cond) && !rcu_read_lock_any_held(), \ |
28875945 | 64 | "RCU-list traversed in non-reader section!"); \ |
4dfd5cd8 | 65 | }) |
28875945 JFG |
66 | #else |
67 | #define __list_check_rcu(dummy, cond, extra...) \ | |
68 | ({ check_arg_count_one(extra); }) | |
69 | #endif | |
70 | ||
82524746 FBH |
71 | /* |
72 | * Insert a new entry between two known consecutive entries. | |
73 | * | |
74 | * This is only for internal list manipulation where we know | |
75 | * the prev/next entries already! | |
76 | */ | |
77 | static inline void __list_add_rcu(struct list_head *new, | |
78 | struct list_head *prev, struct list_head *next) | |
79 | { | |
54acd439 KC |
80 | if (!__list_add_valid(new, prev, next)) |
81 | return; | |
82 | ||
82524746 FBH |
83 | new->next = next; |
84 | new->prev = prev; | |
67bdbffd | 85 | rcu_assign_pointer(list_next_rcu(prev), new); |
82524746 | 86 | next->prev = new; |
82524746 FBH |
87 | } |
88 | ||
89 | /** | |
90 | * list_add_rcu - add a new entry to rcu-protected list | |
91 | * @new: new entry to be added | |
92 | * @head: list head to add it after | |
93 | * | |
94 | * Insert a new entry after the specified head. | |
95 | * This is good for implementing stacks. | |
96 | * | |
97 | * The caller must take whatever precautions are necessary | |
98 | * (such as holding appropriate locks) to avoid racing | |
99 | * with another list-mutation primitive, such as list_add_rcu() | |
100 | * or list_del_rcu(), running on this same list. | |
101 | * However, it is perfectly legal to run concurrently with | |
102 | * the _rcu list-traversal primitives, such as | |
103 | * list_for_each_entry_rcu(). | |
104 | */ | |
105 | static inline void list_add_rcu(struct list_head *new, struct list_head *head) | |
106 | { | |
107 | __list_add_rcu(new, head, head->next); | |
108 | } | |
109 | ||
110 | /** | |
111 | * list_add_tail_rcu - add a new entry to rcu-protected list | |
112 | * @new: new entry to be added | |
113 | * @head: list head to add it before | |
114 | * | |
115 | * Insert a new entry before the specified head. | |
116 | * This is useful for implementing queues. | |
117 | * | |
118 | * The caller must take whatever precautions are necessary | |
119 | * (such as holding appropriate locks) to avoid racing | |
120 | * with another list-mutation primitive, such as list_add_tail_rcu() | |
121 | * or list_del_rcu(), running on this same list. | |
122 | * However, it is perfectly legal to run concurrently with | |
123 | * the _rcu list-traversal primitives, such as | |
124 | * list_for_each_entry_rcu(). | |
125 | */ | |
126 | static inline void list_add_tail_rcu(struct list_head *new, | |
127 | struct list_head *head) | |
128 | { | |
129 | __list_add_rcu(new, head->prev, head); | |
130 | } | |
131 | ||
132 | /** | |
133 | * list_del_rcu - deletes entry from list without re-initialization | |
134 | * @entry: the element to delete from the list. | |
135 | * | |
136 | * Note: list_empty() on entry does not return true after this, | |
137 | * the entry is in an undefined state. It is useful for RCU based | |
138 | * lockfree traversal. | |
139 | * | |
140 | * In particular, it means that we can not poison the forward | |
141 | * pointers that may still be used for walking the list. | |
142 | * | |
143 | * The caller must take whatever precautions are necessary | |
144 | * (such as holding appropriate locks) to avoid racing | |
145 | * with another list-mutation primitive, such as list_del_rcu() | |
146 | * or list_add_rcu(), running on this same list. | |
147 | * However, it is perfectly legal to run concurrently with | |
148 | * the _rcu list-traversal primitives, such as | |
149 | * list_for_each_entry_rcu(). | |
150 | * | |
151 | * Note that the caller is not permitted to immediately free | |
152 | * the newly deleted entry. Instead, either synchronize_rcu() | |
153 | * or call_rcu() must be used to defer freeing until an RCU | |
154 | * grace period has elapsed. | |
155 | */ | |
156 | static inline void list_del_rcu(struct list_head *entry) | |
157 | { | |
559f9bad | 158 | __list_del_entry(entry); |
82524746 FBH |
159 | entry->prev = LIST_POISON2; |
160 | } | |
161 | ||
6beeac76 AA |
162 | /** |
163 | * hlist_del_init_rcu - deletes entry from hash list with re-initialization | |
164 | * @n: the element to delete from the hash list. | |
165 | * | |
166 | * Note: list_unhashed() on the node return true after this. It is | |
167 | * useful for RCU based read lockfree traversal if the writer side | |
168 | * must know if the list entry is still hashed or already unhashed. | |
169 | * | |
170 | * In particular, it means that we can not poison the forward pointers | |
171 | * that may still be used for walking the hash list and we can only | |
172 | * zero the pprev pointer so list_unhashed() will return true after | |
173 | * this. | |
174 | * | |
175 | * The caller must take whatever precautions are necessary (such as | |
176 | * holding appropriate locks) to avoid racing with another | |
177 | * list-mutation primitive, such as hlist_add_head_rcu() or | |
178 | * hlist_del_rcu(), running on this same list. However, it is | |
179 | * perfectly legal to run concurrently with the _rcu list-traversal | |
180 | * primitives, such as hlist_for_each_entry_rcu(). | |
181 | */ | |
182 | static inline void hlist_del_init_rcu(struct hlist_node *n) | |
183 | { | |
184 | if (!hlist_unhashed(n)) { | |
185 | __hlist_del(n); | |
c54a2744 | 186 | WRITE_ONCE(n->pprev, NULL); |
6beeac76 AA |
187 | } |
188 | } | |
189 | ||
82524746 FBH |
190 | /** |
191 | * list_replace_rcu - replace old entry by new one | |
192 | * @old : the element to be replaced | |
193 | * @new : the new element to insert | |
194 | * | |
195 | * The @old entry will be replaced with the @new entry atomically. | |
196 | * Note: @old should not be empty. | |
197 | */ | |
198 | static inline void list_replace_rcu(struct list_head *old, | |
199 | struct list_head *new) | |
200 | { | |
201 | new->next = old->next; | |
202 | new->prev = old->prev; | |
67bdbffd | 203 | rcu_assign_pointer(list_next_rcu(new->prev), new); |
82524746 | 204 | new->next->prev = new; |
82524746 FBH |
205 | old->prev = LIST_POISON2; |
206 | } | |
207 | ||
208 | /** | |
7d86dccf | 209 | * __list_splice_init_rcu - join an RCU-protected list into an existing list. |
82524746 | 210 | * @list: the RCU-protected list to splice |
7d86dccf PM |
211 | * @prev: points to the last element of the existing list |
212 | * @next: points to the first element of the existing list | |
aff5f036 | 213 | * @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
82524746 | 214 | * |
7d86dccf PM |
215 | * The list pointed to by @prev and @next can be RCU-read traversed |
216 | * concurrently with this function. | |
82524746 FBH |
217 | * |
218 | * Note that this function blocks. | |
219 | * | |
7d86dccf PM |
220 | * Important note: the caller must take whatever action is necessary to prevent |
221 | * any other updates to the existing list. In principle, it is possible to | |
222 | * modify the list as soon as sync() begins execution. If this sort of thing | |
223 | * becomes necessary, an alternative version based on call_rcu() could be | |
224 | * created. But only if -really- needed -- there is no shortage of RCU API | |
225 | * members. | |
82524746 | 226 | */ |
7d86dccf PM |
227 | static inline void __list_splice_init_rcu(struct list_head *list, |
228 | struct list_head *prev, | |
229 | struct list_head *next, | |
230 | void (*sync)(void)) | |
82524746 FBH |
231 | { |
232 | struct list_head *first = list->next; | |
233 | struct list_head *last = list->prev; | |
82524746 | 234 | |
2a855b64 PM |
235 | /* |
236 | * "first" and "last" tracking list, so initialize it. RCU readers | |
237 | * have access to this list, so we must use INIT_LIST_HEAD_RCU() | |
238 | * instead of INIT_LIST_HEAD(). | |
239 | */ | |
82524746 | 240 | |
2a855b64 | 241 | INIT_LIST_HEAD_RCU(list); |
82524746 FBH |
242 | |
243 | /* | |
244 | * At this point, the list body still points to the source list. | |
245 | * Wait for any readers to finish using the list before splicing | |
246 | * the list body into the new list. Any new readers will see | |
247 | * an empty list. | |
248 | */ | |
249 | ||
250 | sync(); | |
c93773c1 PM |
251 | ASSERT_EXCLUSIVE_ACCESS(*first); |
252 | ASSERT_EXCLUSIVE_ACCESS(*last); | |
82524746 FBH |
253 | |
254 | /* | |
255 | * Readers are finished with the source list, so perform splice. | |
256 | * The order is important if the new list is global and accessible | |
257 | * to concurrent RCU readers. Note that RCU readers are not | |
258 | * permitted to traverse the prev pointers without excluding | |
259 | * this function. | |
260 | */ | |
261 | ||
7d86dccf PM |
262 | last->next = next; |
263 | rcu_assign_pointer(list_next_rcu(prev), first); | |
264 | first->prev = prev; | |
265 | next->prev = last; | |
266 | } | |
267 | ||
268 | /** | |
269 | * list_splice_init_rcu - splice an RCU-protected list into an existing list, | |
270 | * designed for stacks. | |
271 | * @list: the RCU-protected list to splice | |
272 | * @head: the place in the existing list to splice the first list into | |
aff5f036 | 273 | * @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
7d86dccf PM |
274 | */ |
275 | static inline void list_splice_init_rcu(struct list_head *list, | |
276 | struct list_head *head, | |
277 | void (*sync)(void)) | |
278 | { | |
279 | if (!list_empty(list)) | |
280 | __list_splice_init_rcu(list, head, head->next, sync); | |
281 | } | |
282 | ||
283 | /** | |
284 | * list_splice_tail_init_rcu - splice an RCU-protected list into an existing | |
285 | * list, designed for queues. | |
286 | * @list: the RCU-protected list to splice | |
287 | * @head: the place in the existing list to splice the first list into | |
aff5f036 | 288 | * @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
7d86dccf PM |
289 | */ |
290 | static inline void list_splice_tail_init_rcu(struct list_head *list, | |
291 | struct list_head *head, | |
292 | void (*sync)(void)) | |
293 | { | |
294 | if (!list_empty(list)) | |
295 | __list_splice_init_rcu(list, head->prev, head, sync); | |
82524746 FBH |
296 | } |
297 | ||
72c6a987 JP |
298 | /** |
299 | * list_entry_rcu - get the struct for this entry | |
300 | * @ptr: the &struct list_head pointer. | |
301 | * @type: the type of the struct this is embedded in. | |
3943f42c | 302 | * @member: the name of the list_head within the struct. |
72c6a987 JP |
303 | * |
304 | * This primitive may safely run concurrently with the _rcu list-mutation | |
305 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). | |
306 | */ | |
307 | #define list_entry_rcu(ptr, type, member) \ | |
506458ef | 308 | container_of(READ_ONCE(ptr), type, member) |
72c6a987 | 309 | |
27fdb35f | 310 | /* |
f88022a4 MM |
311 | * Where are list_empty_rcu() and list_first_entry_rcu()? |
312 | * | |
313 | * Implementing those functions following their counterparts list_empty() and | |
314 | * list_first_entry() is not advisable because they lead to subtle race | |
315 | * conditions as the following snippet shows: | |
316 | * | |
317 | * if (!list_empty_rcu(mylist)) { | |
318 | * struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member); | |
319 | * do_something(bar); | |
320 | * } | |
321 | * | |
322 | * The list may not be empty when list_empty_rcu checks it, but it may be when | |
323 | * list_first_entry_rcu rereads the ->next pointer. | |
324 | * | |
325 | * Rereading the ->next pointer is not a problem for list_empty() and | |
326 | * list_first_entry() because they would be protected by a lock that blocks | |
327 | * writers. | |
328 | * | |
329 | * See list_first_or_null_rcu for an alternative. | |
330 | */ | |
331 | ||
332 | /** | |
333 | * list_first_or_null_rcu - get the first element from a list | |
72c6a987 JP |
334 | * @ptr: the list head to take the element from. |
335 | * @type: the type of the struct this is embedded in. | |
3943f42c | 336 | * @member: the name of the list_head within the struct. |
72c6a987 | 337 | * |
f88022a4 | 338 | * Note that if the list is empty, it returns NULL. |
72c6a987 JP |
339 | * |
340 | * This primitive may safely run concurrently with the _rcu list-mutation | |
341 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). | |
342 | */ | |
f88022a4 | 343 | #define list_first_or_null_rcu(ptr, type, member) \ |
0adab9b9 JP |
344 | ({ \ |
345 | struct list_head *__ptr = (ptr); \ | |
7d0ae808 | 346 | struct list_head *__next = READ_ONCE(__ptr->next); \ |
0adab9b9 JP |
347 | likely(__ptr != __next) ? list_entry_rcu(__next, type, member) : NULL; \ |
348 | }) | |
72c6a987 | 349 | |
ff3c44e6 TH |
350 | /** |
351 | * list_next_or_null_rcu - get the first element from a list | |
352 | * @head: the head for the list. | |
353 | * @ptr: the list head to take the next element from. | |
354 | * @type: the type of the struct this is embedded in. | |
355 | * @member: the name of the list_head within the struct. | |
356 | * | |
357 | * Note that if the ptr is at the end of the list, NULL is returned. | |
358 | * | |
359 | * This primitive may safely run concurrently with the _rcu list-mutation | |
360 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). | |
361 | */ | |
362 | #define list_next_or_null_rcu(head, ptr, type, member) \ | |
363 | ({ \ | |
364 | struct list_head *__head = (head); \ | |
365 | struct list_head *__ptr = (ptr); \ | |
366 | struct list_head *__next = READ_ONCE(__ptr->next); \ | |
367 | likely(__next != __head) ? list_entry_rcu(__next, type, \ | |
368 | member) : NULL; \ | |
369 | }) | |
370 | ||
82524746 FBH |
371 | /** |
372 | * list_for_each_entry_rcu - iterate over rcu list of given type | |
373 | * @pos: the type * to use as a loop cursor. | |
374 | * @head: the head for your list. | |
3943f42c | 375 | * @member: the name of the list_head within the struct. |
ddc46593 | 376 | * @cond: optional lockdep expression if called from non-RCU protection. |
82524746 FBH |
377 | * |
378 | * This list-traversal primitive may safely run concurrently with | |
379 | * the _rcu list-mutation primitives such as list_add_rcu() | |
380 | * as long as the traversal is guarded by rcu_read_lock(). | |
381 | */ | |
28875945 JFG |
382 | #define list_for_each_entry_rcu(pos, head, member, cond...) \ |
383 | for (__list_check_rcu(dummy, ## cond, 0), \ | |
384 | pos = list_entry_rcu((head)->next, typeof(*pos), member); \ | |
385 | &pos->member != (head); \ | |
72c6a987 | 386 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
82524746 | 387 | |
69b90729 AK |
388 | /** |
389 | * list_entry_lockless - get the struct for this entry | |
390 | * @ptr: the &struct list_head pointer. | |
391 | * @type: the type of the struct this is embedded in. | |
392 | * @member: the name of the list_head within the struct. | |
393 | * | |
aff5f036 PM |
394 | * This primitive may safely run concurrently with the _rcu |
395 | * list-mutation primitives such as list_add_rcu(), but requires some | |
396 | * implicit RCU read-side guarding. One example is running within a special | |
397 | * exception-time environment where preemption is disabled and where lockdep | |
398 | * cannot be invoked. Another example is when items are added to the list, | |
399 | * but never deleted. | |
69b90729 AK |
400 | */ |
401 | #define list_entry_lockless(ptr, type, member) \ | |
506458ef | 402 | container_of((typeof(ptr))READ_ONCE(ptr), type, member) |
69b90729 AK |
403 | |
404 | /** | |
405 | * list_for_each_entry_lockless - iterate over rcu list of given type | |
406 | * @pos: the type * to use as a loop cursor. | |
407 | * @head: the head for your list. | |
408 | * @member: the name of the list_struct within the struct. | |
409 | * | |
aff5f036 PM |
410 | * This primitive may safely run concurrently with the _rcu |
411 | * list-mutation primitives such as list_add_rcu(), but requires some | |
412 | * implicit RCU read-side guarding. One example is running within a special | |
413 | * exception-time environment where preemption is disabled and where lockdep | |
414 | * cannot be invoked. Another example is when items are added to the list, | |
415 | * but never deleted. | |
69b90729 AK |
416 | */ |
417 | #define list_for_each_entry_lockless(pos, head, member) \ | |
418 | for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \ | |
419 | &pos->member != (head); \ | |
420 | pos = list_entry_lockless(pos->member.next, typeof(*pos), member)) | |
421 | ||
254245d2 | 422 | /** |
423 | * list_for_each_entry_continue_rcu - continue iteration over list of given type | |
424 | * @pos: the type * to use as a loop cursor. | |
425 | * @head: the head for your list. | |
3943f42c | 426 | * @member: the name of the list_head within the struct. |
254245d2 | 427 | * |
428 | * Continue to iterate over list of given type, continuing after | |
b7b6f94c N |
429 | * the current position which must have been in the list when the RCU read |
430 | * lock was taken. | |
431 | * This would typically require either that you obtained the node from a | |
432 | * previous walk of the list in the same RCU read-side critical section, or | |
433 | * that you held some sort of non-RCU reference (such as a reference count) | |
434 | * to keep the node alive *and* in the list. | |
435 | * | |
436 | * This iterator is similar to list_for_each_entry_from_rcu() except | |
437 | * this starts after the given position and that one starts at the given | |
438 | * position. | |
254245d2 | 439 | */ |
440 | #define list_for_each_entry_continue_rcu(pos, head, member) \ | |
441 | for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \ | |
e66eed65 | 442 | &pos->member != (head); \ |
254245d2 | 443 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
444 | ||
ead9ad72 N |
445 | /** |
446 | * list_for_each_entry_from_rcu - iterate over a list from current point | |
447 | * @pos: the type * to use as a loop cursor. | |
448 | * @head: the head for your list. | |
449 | * @member: the name of the list_node within the struct. | |
450 | * | |
451 | * Iterate over the tail of a list starting from a given position, | |
452 | * which must have been in the list when the RCU read lock was taken. | |
b7b6f94c N |
453 | * This would typically require either that you obtained the node from a |
454 | * previous walk of the list in the same RCU read-side critical section, or | |
455 | * that you held some sort of non-RCU reference (such as a reference count) | |
456 | * to keep the node alive *and* in the list. | |
457 | * | |
458 | * This iterator is similar to list_for_each_entry_continue_rcu() except | |
459 | * this starts from the given position and that one starts from the position | |
460 | * after the given position. | |
ead9ad72 N |
461 | */ |
462 | #define list_for_each_entry_from_rcu(pos, head, member) \ | |
463 | for (; &(pos)->member != (head); \ | |
464 | pos = list_entry_rcu(pos->member.next, typeof(*(pos)), member)) | |
465 | ||
82524746 FBH |
466 | /** |
467 | * hlist_del_rcu - deletes entry from hash list without re-initialization | |
468 | * @n: the element to delete from the hash list. | |
469 | * | |
470 | * Note: list_unhashed() on entry does not return true after this, | |
471 | * the entry is in an undefined state. It is useful for RCU based | |
472 | * lockfree traversal. | |
473 | * | |
474 | * In particular, it means that we can not poison the forward | |
475 | * pointers that may still be used for walking the hash list. | |
476 | * | |
477 | * The caller must take whatever precautions are necessary | |
478 | * (such as holding appropriate locks) to avoid racing | |
479 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
480 | * or hlist_del_rcu(), running on this same list. | |
481 | * However, it is perfectly legal to run concurrently with | |
482 | * the _rcu list-traversal primitives, such as | |
483 | * hlist_for_each_entry(). | |
484 | */ | |
485 | static inline void hlist_del_rcu(struct hlist_node *n) | |
486 | { | |
487 | __hlist_del(n); | |
c54a2744 | 488 | WRITE_ONCE(n->pprev, LIST_POISON2); |
82524746 FBH |
489 | } |
490 | ||
491 | /** | |
492 | * hlist_replace_rcu - replace old entry by new one | |
493 | * @old : the element to be replaced | |
494 | * @new : the new element to insert | |
495 | * | |
496 | * The @old entry will be replaced with the @new entry atomically. | |
497 | */ | |
498 | static inline void hlist_replace_rcu(struct hlist_node *old, | |
499 | struct hlist_node *new) | |
500 | { | |
501 | struct hlist_node *next = old->next; | |
502 | ||
503 | new->next = next; | |
c54a2744 | 504 | WRITE_ONCE(new->pprev, old->pprev); |
67bdbffd | 505 | rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new); |
82524746 | 506 | if (next) |
c54a2744 ED |
507 | WRITE_ONCE(new->next->pprev, &new->next); |
508 | WRITE_ONCE(old->pprev, LIST_POISON2); | |
82524746 FBH |
509 | } |
510 | ||
35fc0e3b EB |
511 | /** |
512 | * hlists_swap_heads_rcu - swap the lists the hlist heads point to | |
513 | * @left: The hlist head on the left | |
514 | * @right: The hlist head on the right | |
515 | * | |
516 | * The lists start out as [@left ][node1 ... ] and | |
24692fa2 | 517 | * [@right ][node2 ... ] |
35fc0e3b EB |
518 | * The lists end up as [@left ][node2 ... ] |
519 | * [@right ][node1 ... ] | |
520 | */ | |
521 | static inline void hlists_swap_heads_rcu(struct hlist_head *left, struct hlist_head *right) | |
522 | { | |
523 | struct hlist_node *node1 = left->first; | |
524 | struct hlist_node *node2 = right->first; | |
525 | ||
526 | rcu_assign_pointer(left->first, node2); | |
527 | rcu_assign_pointer(right->first, node1); | |
528 | WRITE_ONCE(node2->pprev, &left->first); | |
529 | WRITE_ONCE(node1->pprev, &right->first); | |
530 | } | |
531 | ||
67bdbffd AB |
532 | /* |
533 | * return the first or the next element in an RCU protected hlist | |
534 | */ | |
535 | #define hlist_first_rcu(head) (*((struct hlist_node __rcu **)(&(head)->first))) | |
536 | #define hlist_next_rcu(node) (*((struct hlist_node __rcu **)(&(node)->next))) | |
537 | #define hlist_pprev_rcu(node) (*((struct hlist_node __rcu **)((node)->pprev))) | |
538 | ||
82524746 FBH |
539 | /** |
540 | * hlist_add_head_rcu | |
541 | * @n: the element to add to the hash list. | |
542 | * @h: the list to add to. | |
543 | * | |
544 | * Description: | |
545 | * Adds the specified element to the specified hlist, | |
546 | * while permitting racing traversals. | |
547 | * | |
548 | * The caller must take whatever precautions are necessary | |
549 | * (such as holding appropriate locks) to avoid racing | |
550 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
551 | * or hlist_del_rcu(), running on this same list. | |
552 | * However, it is perfectly legal to run concurrently with | |
553 | * the _rcu list-traversal primitives, such as | |
554 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
555 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
556 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
557 | */ | |
558 | static inline void hlist_add_head_rcu(struct hlist_node *n, | |
559 | struct hlist_head *h) | |
560 | { | |
561 | struct hlist_node *first = h->first; | |
10aa9d2c | 562 | |
82524746 | 563 | n->next = first; |
c54a2744 | 564 | WRITE_ONCE(n->pprev, &h->first); |
67bdbffd | 565 | rcu_assign_pointer(hlist_first_rcu(h), n); |
82524746 | 566 | if (first) |
c54a2744 | 567 | WRITE_ONCE(first->pprev, &n->next); |
82524746 FBH |
568 | } |
569 | ||
1602f49b DM |
570 | /** |
571 | * hlist_add_tail_rcu | |
572 | * @n: the element to add to the hash list. | |
573 | * @h: the list to add to. | |
574 | * | |
575 | * Description: | |
576 | * Adds the specified element to the specified hlist, | |
577 | * while permitting racing traversals. | |
578 | * | |
579 | * The caller must take whatever precautions are necessary | |
580 | * (such as holding appropriate locks) to avoid racing | |
581 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
582 | * or hlist_del_rcu(), running on this same list. | |
583 | * However, it is perfectly legal to run concurrently with | |
584 | * the _rcu list-traversal primitives, such as | |
585 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
586 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
587 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
588 | */ | |
589 | static inline void hlist_add_tail_rcu(struct hlist_node *n, | |
590 | struct hlist_head *h) | |
591 | { | |
592 | struct hlist_node *i, *last = NULL; | |
593 | ||
48ac3466 MT |
594 | /* Note: write side code, so rcu accessors are not needed. */ |
595 | for (i = h->first; i; i = i->next) | |
1602f49b DM |
596 | last = i; |
597 | ||
598 | if (last) { | |
599 | n->next = last->next; | |
c54a2744 | 600 | WRITE_ONCE(n->pprev, &last->next); |
1602f49b DM |
601 | rcu_assign_pointer(hlist_next_rcu(last), n); |
602 | } else { | |
603 | hlist_add_head_rcu(n, h); | |
604 | } | |
605 | } | |
606 | ||
82524746 FBH |
607 | /** |
608 | * hlist_add_before_rcu | |
609 | * @n: the new element to add to the hash list. | |
610 | * @next: the existing element to add the new element before. | |
611 | * | |
612 | * Description: | |
613 | * Adds the specified element to the specified hlist | |
614 | * before the specified node while permitting racing traversals. | |
615 | * | |
616 | * The caller must take whatever precautions are necessary | |
617 | * (such as holding appropriate locks) to avoid racing | |
618 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
619 | * or hlist_del_rcu(), running on this same list. | |
620 | * However, it is perfectly legal to run concurrently with | |
621 | * the _rcu list-traversal primitives, such as | |
622 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
623 | * problems on Alpha CPUs. | |
624 | */ | |
625 | static inline void hlist_add_before_rcu(struct hlist_node *n, | |
626 | struct hlist_node *next) | |
627 | { | |
c54a2744 | 628 | WRITE_ONCE(n->pprev, next->pprev); |
82524746 | 629 | n->next = next; |
67bdbffd | 630 | rcu_assign_pointer(hlist_pprev_rcu(n), n); |
c54a2744 | 631 | WRITE_ONCE(next->pprev, &n->next); |
82524746 FBH |
632 | } |
633 | ||
634 | /** | |
1d023284 | 635 | * hlist_add_behind_rcu |
82524746 | 636 | * @n: the new element to add to the hash list. |
1d023284 | 637 | * @prev: the existing element to add the new element after. |
82524746 FBH |
638 | * |
639 | * Description: | |
640 | * Adds the specified element to the specified hlist | |
641 | * after the specified node while permitting racing traversals. | |
642 | * | |
643 | * The caller must take whatever precautions are necessary | |
644 | * (such as holding appropriate locks) to avoid racing | |
645 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
646 | * or hlist_del_rcu(), running on this same list. | |
647 | * However, it is perfectly legal to run concurrently with | |
648 | * the _rcu list-traversal primitives, such as | |
649 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
650 | * problems on Alpha CPUs. | |
651 | */ | |
1d023284 KH |
652 | static inline void hlist_add_behind_rcu(struct hlist_node *n, |
653 | struct hlist_node *prev) | |
82524746 FBH |
654 | { |
655 | n->next = prev->next; | |
c54a2744 | 656 | WRITE_ONCE(n->pprev, &prev->next); |
67bdbffd | 657 | rcu_assign_pointer(hlist_next_rcu(prev), n); |
82524746 | 658 | if (n->next) |
c54a2744 | 659 | WRITE_ONCE(n->next->pprev, &n->next); |
82524746 FBH |
660 | } |
661 | ||
67bdbffd AB |
662 | #define __hlist_for_each_rcu(pos, head) \ |
663 | for (pos = rcu_dereference(hlist_first_rcu(head)); \ | |
75d65a42 | 664 | pos; \ |
67bdbffd | 665 | pos = rcu_dereference(hlist_next_rcu(pos))) |
1cc52327 | 666 | |
82524746 FBH |
667 | /** |
668 | * hlist_for_each_entry_rcu - iterate over rcu list of given type | |
b67bfe0d | 669 | * @pos: the type * to use as a loop cursor. |
82524746 FBH |
670 | * @head: the head for your list. |
671 | * @member: the name of the hlist_node within the struct. | |
ddc46593 | 672 | * @cond: optional lockdep expression if called from non-RCU protection. |
82524746 FBH |
673 | * |
674 | * This list-traversal primitive may safely run concurrently with | |
675 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
676 | * as long as the traversal is guarded by rcu_read_lock(). | |
677 | */ | |
28875945 JFG |
678 | #define hlist_for_each_entry_rcu(pos, head, member, cond...) \ |
679 | for (__list_check_rcu(dummy, ## cond, 0), \ | |
680 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\ | |
b67bfe0d SL |
681 | typeof(*(pos)), member); \ |
682 | pos; \ | |
683 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\ | |
684 | &(pos)->member)), typeof(*(pos)), member)) | |
82524746 | 685 | |
12bcbe66 SR |
686 | /** |
687 | * hlist_for_each_entry_rcu_notrace - iterate over rcu list of given type (for tracing) | |
688 | * @pos: the type * to use as a loop cursor. | |
689 | * @head: the head for your list. | |
690 | * @member: the name of the hlist_node within the struct. | |
691 | * | |
692 | * This list-traversal primitive may safely run concurrently with | |
693 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
694 | * as long as the traversal is guarded by rcu_read_lock(). | |
695 | * | |
696 | * This is the same as hlist_for_each_entry_rcu() except that it does | |
697 | * not do any RCU debugging or tracing. | |
698 | */ | |
699 | #define hlist_for_each_entry_rcu_notrace(pos, head, member) \ | |
0a5b99f5 | 700 | for (pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_first_rcu(head)),\ |
12bcbe66 SR |
701 | typeof(*(pos)), member); \ |
702 | pos; \ | |
0a5b99f5 | 703 | pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_next_rcu(\ |
12bcbe66 SR |
704 | &(pos)->member)), typeof(*(pos)), member)) |
705 | ||
4f70ecca ED |
706 | /** |
707 | * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type | |
b67bfe0d | 708 | * @pos: the type * to use as a loop cursor. |
4f70ecca ED |
709 | * @head: the head for your list. |
710 | * @member: the name of the hlist_node within the struct. | |
711 | * | |
712 | * This list-traversal primitive may safely run concurrently with | |
713 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
714 | * as long as the traversal is guarded by rcu_read_lock(). | |
715 | */ | |
b67bfe0d SL |
716 | #define hlist_for_each_entry_rcu_bh(pos, head, member) \ |
717 | for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_first_rcu(head)),\ | |
718 | typeof(*(pos)), member); \ | |
719 | pos; \ | |
720 | pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(\ | |
721 | &(pos)->member)), typeof(*(pos)), member)) | |
4f70ecca | 722 | |
5c578aed | 723 | /** |
724 | * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point | |
b67bfe0d | 725 | * @pos: the type * to use as a loop cursor. |
5c578aed | 726 | * @member: the name of the hlist_node within the struct. |
727 | */ | |
b67bfe0d | 728 | #define hlist_for_each_entry_continue_rcu(pos, member) \ |
f520c98e YX |
729 | for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
730 | &(pos)->member)), typeof(*(pos)), member); \ | |
b67bfe0d | 731 | pos; \ |
f520c98e YX |
732 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
733 | &(pos)->member)), typeof(*(pos)), member)) | |
5c578aed | 734 | |
4f70ecca ED |
735 | /** |
736 | * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point | |
b67bfe0d | 737 | * @pos: the type * to use as a loop cursor. |
4f70ecca ED |
738 | * @member: the name of the hlist_node within the struct. |
739 | */ | |
b67bfe0d | 740 | #define hlist_for_each_entry_continue_rcu_bh(pos, member) \ |
f520c98e YX |
741 | for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \ |
742 | &(pos)->member)), typeof(*(pos)), member); \ | |
b67bfe0d | 743 | pos; \ |
f520c98e YX |
744 | pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \ |
745 | &(pos)->member)), typeof(*(pos)), member)) | |
4f70ecca | 746 | |
97ede29e YX |
747 | /** |
748 | * hlist_for_each_entry_from_rcu - iterate over a hlist continuing from current point | |
749 | * @pos: the type * to use as a loop cursor. | |
750 | * @member: the name of the hlist_node within the struct. | |
751 | */ | |
752 | #define hlist_for_each_entry_from_rcu(pos, member) \ | |
753 | for (; pos; \ | |
f517700c YX |
754 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
755 | &(pos)->member)), typeof(*(pos)), member)) | |
5c578aed | 756 | |
82524746 FBH |
757 | #endif /* __KERNEL__ */ |
758 | #endif |