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 | |
2a855b64 PM |
13 | /* |
14 | * INIT_LIST_HEAD_RCU - Initialize a list_head visible to RCU readers | |
15 | * @list: list to be initialized | |
16 | * | |
17 | * You should instead use INIT_LIST_HEAD() for normal initialization and | |
18 | * cleanup tasks, when readers have no access to the list being initialized. | |
19 | * However, if the list being initialized is visible to readers, you | |
20 | * need to keep the compiler from being too mischievous. | |
21 | */ | |
22 | static inline void INIT_LIST_HEAD_RCU(struct list_head *list) | |
23 | { | |
7d0ae808 PM |
24 | WRITE_ONCE(list->next, list); |
25 | WRITE_ONCE(list->prev, list); | |
2a855b64 PM |
26 | } |
27 | ||
67bdbffd AB |
28 | /* |
29 | * return the ->next pointer of a list_head in an rcu safe | |
30 | * way, we must not access it directly | |
31 | */ | |
32 | #define list_next_rcu(list) (*((struct list_head __rcu **)(&(list)->next))) | |
33 | ||
afa47fdf MB |
34 | /** |
35 | * list_tail_rcu - returns the prev pointer of the head of the list | |
36 | * @head: the head of the list | |
37 | * | |
38 | * Note: This should only be used with the list header, and even then | |
39 | * only if list_del() and similar primitives are not also used on the | |
40 | * list header. | |
41 | */ | |
42 | #define list_tail_rcu(head) (*((struct list_head __rcu **)(&(head)->prev))) | |
43 | ||
28875945 JFG |
44 | /* |
45 | * Check during list traversal that we are within an RCU reader | |
46 | */ | |
47 | ||
48 | #define check_arg_count_one(dummy) | |
49 | ||
50 | #ifdef CONFIG_PROVE_RCU_LIST | |
51 | #define __list_check_rcu(dummy, cond, extra...) \ | |
52 | ({ \ | |
53 | check_arg_count_one(extra); \ | |
4dfd5cd8 | 54 | RCU_LOCKDEP_WARN(!(cond) && !rcu_read_lock_any_held(), \ |
28875945 | 55 | "RCU-list traversed in non-reader section!"); \ |
4dfd5cd8 | 56 | }) |
ae2212a7 MB |
57 | |
58 | #define __list_check_srcu(cond) \ | |
59 | ({ \ | |
60 | RCU_LOCKDEP_WARN(!(cond), \ | |
61 | "RCU-list traversed without holding the required lock!");\ | |
62 | }) | |
28875945 JFG |
63 | #else |
64 | #define __list_check_rcu(dummy, cond, extra...) \ | |
65 | ({ check_arg_count_one(extra); }) | |
ae2212a7 MB |
66 | |
67 | #define __list_check_srcu(cond) ({ }) | |
28875945 JFG |
68 | #endif |
69 | ||
82524746 FBH |
70 | /* |
71 | * Insert a new entry between two known consecutive entries. | |
72 | * | |
73 | * This is only for internal list manipulation where we know | |
74 | * the prev/next entries already! | |
75 | */ | |
76 | static inline void __list_add_rcu(struct list_head *new, | |
77 | struct list_head *prev, struct list_head *next) | |
78 | { | |
54acd439 KC |
79 | if (!__list_add_valid(new, prev, next)) |
80 | return; | |
81 | ||
82524746 FBH |
82 | new->next = next; |
83 | new->prev = prev; | |
67bdbffd | 84 | rcu_assign_pointer(list_next_rcu(prev), new); |
82524746 | 85 | next->prev = new; |
82524746 FBH |
86 | } |
87 | ||
88 | /** | |
89 | * list_add_rcu - add a new entry to rcu-protected list | |
90 | * @new: new entry to be added | |
91 | * @head: list head to add it after | |
92 | * | |
93 | * Insert a new entry after the specified head. | |
94 | * This is good for implementing stacks. | |
95 | * | |
96 | * The caller must take whatever precautions are necessary | |
97 | * (such as holding appropriate locks) to avoid racing | |
98 | * with another list-mutation primitive, such as list_add_rcu() | |
99 | * or list_del_rcu(), running on this same list. | |
100 | * However, it is perfectly legal to run concurrently with | |
101 | * the _rcu list-traversal primitives, such as | |
102 | * list_for_each_entry_rcu(). | |
103 | */ | |
104 | static inline void list_add_rcu(struct list_head *new, struct list_head *head) | |
105 | { | |
106 | __list_add_rcu(new, head, head->next); | |
107 | } | |
108 | ||
109 | /** | |
110 | * list_add_tail_rcu - add a new entry to rcu-protected list | |
111 | * @new: new entry to be added | |
112 | * @head: list head to add it before | |
113 | * | |
114 | * Insert a new entry before the specified head. | |
115 | * This is useful for implementing queues. | |
116 | * | |
117 | * The caller must take whatever precautions are necessary | |
118 | * (such as holding appropriate locks) to avoid racing | |
119 | * with another list-mutation primitive, such as list_add_tail_rcu() | |
120 | * or list_del_rcu(), running on this same list. | |
121 | * However, it is perfectly legal to run concurrently with | |
122 | * the _rcu list-traversal primitives, such as | |
123 | * list_for_each_entry_rcu(). | |
124 | */ | |
125 | static inline void list_add_tail_rcu(struct list_head *new, | |
126 | struct list_head *head) | |
127 | { | |
128 | __list_add_rcu(new, head->prev, head); | |
129 | } | |
130 | ||
131 | /** | |
132 | * list_del_rcu - deletes entry from list without re-initialization | |
133 | * @entry: the element to delete from the list. | |
134 | * | |
135 | * Note: list_empty() on entry does not return true after this, | |
136 | * the entry is in an undefined state. It is useful for RCU based | |
137 | * lockfree traversal. | |
138 | * | |
139 | * In particular, it means that we can not poison the forward | |
140 | * pointers that may still be used for walking the list. | |
141 | * | |
142 | * The caller must take whatever precautions are necessary | |
143 | * (such as holding appropriate locks) to avoid racing | |
144 | * with another list-mutation primitive, such as list_del_rcu() | |
145 | * or list_add_rcu(), running on this same list. | |
146 | * However, it is perfectly legal to run concurrently with | |
147 | * the _rcu list-traversal primitives, such as | |
148 | * list_for_each_entry_rcu(). | |
149 | * | |
150 | * Note that the caller is not permitted to immediately free | |
151 | * the newly deleted entry. Instead, either synchronize_rcu() | |
152 | * or call_rcu() must be used to defer freeing until an RCU | |
153 | * grace period has elapsed. | |
154 | */ | |
155 | static inline void list_del_rcu(struct list_head *entry) | |
156 | { | |
559f9bad | 157 | __list_del_entry(entry); |
82524746 FBH |
158 | entry->prev = LIST_POISON2; |
159 | } | |
160 | ||
6beeac76 AA |
161 | /** |
162 | * hlist_del_init_rcu - deletes entry from hash list with re-initialization | |
163 | * @n: the element to delete from the hash list. | |
164 | * | |
165 | * Note: list_unhashed() on the node return true after this. It is | |
166 | * useful for RCU based read lockfree traversal if the writer side | |
167 | * must know if the list entry is still hashed or already unhashed. | |
168 | * | |
169 | * In particular, it means that we can not poison the forward pointers | |
170 | * that may still be used for walking the hash list and we can only | |
171 | * zero the pprev pointer so list_unhashed() will return true after | |
172 | * this. | |
173 | * | |
174 | * The caller must take whatever precautions are necessary (such as | |
175 | * holding appropriate locks) to avoid racing with another | |
176 | * list-mutation primitive, such as hlist_add_head_rcu() or | |
177 | * hlist_del_rcu(), running on this same list. However, it is | |
178 | * perfectly legal to run concurrently with the _rcu list-traversal | |
179 | * primitives, such as hlist_for_each_entry_rcu(). | |
180 | */ | |
181 | static inline void hlist_del_init_rcu(struct hlist_node *n) | |
182 | { | |
183 | if (!hlist_unhashed(n)) { | |
184 | __hlist_del(n); | |
c54a2744 | 185 | WRITE_ONCE(n->pprev, NULL); |
6beeac76 AA |
186 | } |
187 | } | |
188 | ||
82524746 FBH |
189 | /** |
190 | * list_replace_rcu - replace old entry by new one | |
191 | * @old : the element to be replaced | |
192 | * @new : the new element to insert | |
193 | * | |
194 | * The @old entry will be replaced with the @new entry atomically. | |
195 | * Note: @old should not be empty. | |
196 | */ | |
197 | static inline void list_replace_rcu(struct list_head *old, | |
198 | struct list_head *new) | |
199 | { | |
200 | new->next = old->next; | |
201 | new->prev = old->prev; | |
67bdbffd | 202 | rcu_assign_pointer(list_next_rcu(new->prev), new); |
82524746 | 203 | new->next->prev = new; |
82524746 FBH |
204 | old->prev = LIST_POISON2; |
205 | } | |
206 | ||
207 | /** | |
7d86dccf | 208 | * __list_splice_init_rcu - join an RCU-protected list into an existing list. |
82524746 | 209 | * @list: the RCU-protected list to splice |
7d86dccf PM |
210 | * @prev: points to the last element of the existing list |
211 | * @next: points to the first element of the existing list | |
aff5f036 | 212 | * @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
82524746 | 213 | * |
7d86dccf PM |
214 | * The list pointed to by @prev and @next can be RCU-read traversed |
215 | * concurrently with this function. | |
82524746 FBH |
216 | * |
217 | * Note that this function blocks. | |
218 | * | |
7d86dccf PM |
219 | * Important note: the caller must take whatever action is necessary to prevent |
220 | * any other updates to the existing list. In principle, it is possible to | |
221 | * modify the list as soon as sync() begins execution. If this sort of thing | |
222 | * becomes necessary, an alternative version based on call_rcu() could be | |
223 | * created. But only if -really- needed -- there is no shortage of RCU API | |
224 | * members. | |
82524746 | 225 | */ |
7d86dccf PM |
226 | static inline void __list_splice_init_rcu(struct list_head *list, |
227 | struct list_head *prev, | |
228 | struct list_head *next, | |
229 | void (*sync)(void)) | |
82524746 FBH |
230 | { |
231 | struct list_head *first = list->next; | |
232 | struct list_head *last = list->prev; | |
82524746 | 233 | |
2a855b64 PM |
234 | /* |
235 | * "first" and "last" tracking list, so initialize it. RCU readers | |
236 | * have access to this list, so we must use INIT_LIST_HEAD_RCU() | |
237 | * instead of INIT_LIST_HEAD(). | |
238 | */ | |
82524746 | 239 | |
2a855b64 | 240 | INIT_LIST_HEAD_RCU(list); |
82524746 FBH |
241 | |
242 | /* | |
243 | * At this point, the list body still points to the source list. | |
244 | * Wait for any readers to finish using the list before splicing | |
245 | * the list body into the new list. Any new readers will see | |
246 | * an empty list. | |
247 | */ | |
248 | ||
249 | sync(); | |
c93773c1 PM |
250 | ASSERT_EXCLUSIVE_ACCESS(*first); |
251 | ASSERT_EXCLUSIVE_ACCESS(*last); | |
82524746 FBH |
252 | |
253 | /* | |
254 | * Readers are finished with the source list, so perform splice. | |
255 | * The order is important if the new list is global and accessible | |
256 | * to concurrent RCU readers. Note that RCU readers are not | |
257 | * permitted to traverse the prev pointers without excluding | |
258 | * this function. | |
259 | */ | |
260 | ||
7d86dccf PM |
261 | last->next = next; |
262 | rcu_assign_pointer(list_next_rcu(prev), first); | |
263 | first->prev = prev; | |
264 | next->prev = last; | |
265 | } | |
266 | ||
267 | /** | |
268 | * list_splice_init_rcu - splice an RCU-protected list into an existing list, | |
269 | * designed for stacks. | |
270 | * @list: the RCU-protected list to splice | |
271 | * @head: the place in the existing list to splice the first list into | |
aff5f036 | 272 | * @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
7d86dccf PM |
273 | */ |
274 | static inline void list_splice_init_rcu(struct list_head *list, | |
275 | struct list_head *head, | |
276 | void (*sync)(void)) | |
277 | { | |
278 | if (!list_empty(list)) | |
279 | __list_splice_init_rcu(list, head, head->next, sync); | |
280 | } | |
281 | ||
282 | /** | |
283 | * list_splice_tail_init_rcu - splice an RCU-protected list into an existing | |
284 | * list, designed for queues. | |
285 | * @list: the RCU-protected list to splice | |
286 | * @head: the place in the existing list to splice the first list into | |
aff5f036 | 287 | * @sync: synchronize_rcu, synchronize_rcu_expedited, ... |
7d86dccf PM |
288 | */ |
289 | static inline void list_splice_tail_init_rcu(struct list_head *list, | |
290 | struct list_head *head, | |
291 | void (*sync)(void)) | |
292 | { | |
293 | if (!list_empty(list)) | |
294 | __list_splice_init_rcu(list, head->prev, head, sync); | |
82524746 FBH |
295 | } |
296 | ||
72c6a987 JP |
297 | /** |
298 | * list_entry_rcu - get the struct for this entry | |
299 | * @ptr: the &struct list_head pointer. | |
300 | * @type: the type of the struct this is embedded in. | |
3943f42c | 301 | * @member: the name of the list_head within the struct. |
72c6a987 JP |
302 | * |
303 | * This primitive may safely run concurrently with the _rcu list-mutation | |
304 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). | |
305 | */ | |
306 | #define list_entry_rcu(ptr, type, member) \ | |
506458ef | 307 | container_of(READ_ONCE(ptr), type, member) |
72c6a987 | 308 | |
27fdb35f | 309 | /* |
f88022a4 MM |
310 | * Where are list_empty_rcu() and list_first_entry_rcu()? |
311 | * | |
751b1710 | 312 | * They do not exist because they would lead to subtle race conditions: |
f88022a4 MM |
313 | * |
314 | * if (!list_empty_rcu(mylist)) { | |
315 | * struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member); | |
316 | * do_something(bar); | |
317 | * } | |
318 | * | |
751b1710 JW |
319 | * The list might be non-empty when list_empty_rcu() checks it, but it |
320 | * might have become empty by the time that list_first_entry_rcu() rereads | |
321 | * the ->next pointer, which would result in a SEGV. | |
322 | * | |
323 | * When not using RCU, it is OK for list_first_entry() to re-read that | |
324 | * pointer because both functions should be protected by some lock that | |
325 | * blocks writers. | |
f88022a4 | 326 | * |
751b1710 JW |
327 | * When using RCU, list_empty() uses READ_ONCE() to fetch the |
328 | * RCU-protected ->next pointer and then compares it to the address of the | |
329 | * list head. However, it neither dereferences this pointer nor provides | |
330 | * this pointer to its caller. Thus, READ_ONCE() suffices (that is, | |
331 | * rcu_dereference() is not needed), which means that list_empty() can be | |
332 | * used anywhere you would want to use list_empty_rcu(). Just don't | |
333 | * expect anything useful to happen if you do a subsequent lockless | |
334 | * call to list_first_entry_rcu()!!! | |
f88022a4 MM |
335 | * |
336 | * See list_first_or_null_rcu for an alternative. | |
337 | */ | |
338 | ||
339 | /** | |
340 | * list_first_or_null_rcu - get the first element from a list | |
72c6a987 JP |
341 | * @ptr: the list head to take the element from. |
342 | * @type: the type of the struct this is embedded in. | |
3943f42c | 343 | * @member: the name of the list_head within the struct. |
72c6a987 | 344 | * |
f88022a4 | 345 | * Note that if the list is empty, it returns NULL. |
72c6a987 JP |
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 | */ | |
f88022a4 | 350 | #define list_first_or_null_rcu(ptr, type, member) \ |
0adab9b9 JP |
351 | ({ \ |
352 | struct list_head *__ptr = (ptr); \ | |
7d0ae808 | 353 | struct list_head *__next = READ_ONCE(__ptr->next); \ |
0adab9b9 JP |
354 | likely(__ptr != __next) ? list_entry_rcu(__next, type, member) : NULL; \ |
355 | }) | |
72c6a987 | 356 | |
ff3c44e6 TH |
357 | /** |
358 | * list_next_or_null_rcu - get the first element from a list | |
359 | * @head: the head for the list. | |
360 | * @ptr: the list head to take the next element from. | |
361 | * @type: the type of the struct this is embedded in. | |
362 | * @member: the name of the list_head within the struct. | |
363 | * | |
364 | * Note that if the ptr is at the end of the list, NULL is returned. | |
365 | * | |
366 | * This primitive may safely run concurrently with the _rcu list-mutation | |
367 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). | |
368 | */ | |
369 | #define list_next_or_null_rcu(head, ptr, type, member) \ | |
370 | ({ \ | |
371 | struct list_head *__head = (head); \ | |
372 | struct list_head *__ptr = (ptr); \ | |
373 | struct list_head *__next = READ_ONCE(__ptr->next); \ | |
374 | likely(__next != __head) ? list_entry_rcu(__next, type, \ | |
375 | member) : NULL; \ | |
376 | }) | |
377 | ||
82524746 FBH |
378 | /** |
379 | * list_for_each_entry_rcu - iterate over rcu list of given type | |
380 | * @pos: the type * to use as a loop cursor. | |
381 | * @head: the head for your list. | |
3943f42c | 382 | * @member: the name of the list_head within the struct. |
ddc46593 | 383 | * @cond: optional lockdep expression if called from non-RCU protection. |
82524746 FBH |
384 | * |
385 | * This list-traversal primitive may safely run concurrently with | |
386 | * the _rcu list-mutation primitives such as list_add_rcu() | |
387 | * as long as the traversal is guarded by rcu_read_lock(). | |
388 | */ | |
28875945 JFG |
389 | #define list_for_each_entry_rcu(pos, head, member, cond...) \ |
390 | for (__list_check_rcu(dummy, ## cond, 0), \ | |
391 | pos = list_entry_rcu((head)->next, typeof(*pos), member); \ | |
392 | &pos->member != (head); \ | |
72c6a987 | 393 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
82524746 | 394 | |
ae2212a7 MB |
395 | /** |
396 | * list_for_each_entry_srcu - iterate over rcu list of given type | |
397 | * @pos: the type * to use as a loop cursor. | |
398 | * @head: the head for your list. | |
399 | * @member: the name of the list_head within the struct. | |
400 | * @cond: lockdep expression for the lock required to traverse the list. | |
401 | * | |
402 | * This list-traversal primitive may safely run concurrently with | |
403 | * the _rcu list-mutation primitives such as list_add_rcu() | |
404 | * as long as the traversal is guarded by srcu_read_lock(). | |
405 | * The lockdep expression srcu_read_lock_held() can be passed as the | |
406 | * cond argument from read side. | |
407 | */ | |
408 | #define list_for_each_entry_srcu(pos, head, member, cond) \ | |
409 | for (__list_check_srcu(cond), \ | |
410 | pos = list_entry_rcu((head)->next, typeof(*pos), member); \ | |
411 | &pos->member != (head); \ | |
412 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) | |
413 | ||
69b90729 AK |
414 | /** |
415 | * list_entry_lockless - get the struct for this entry | |
416 | * @ptr: the &struct list_head pointer. | |
417 | * @type: the type of the struct this is embedded in. | |
418 | * @member: the name of the list_head within the struct. | |
419 | * | |
aff5f036 PM |
420 | * This primitive may safely run concurrently with the _rcu |
421 | * list-mutation primitives such as list_add_rcu(), but requires some | |
422 | * implicit RCU read-side guarding. One example is running within a special | |
423 | * exception-time environment where preemption is disabled and where lockdep | |
424 | * cannot be invoked. Another example is when items are added to the list, | |
425 | * but never deleted. | |
69b90729 AK |
426 | */ |
427 | #define list_entry_lockless(ptr, type, member) \ | |
506458ef | 428 | container_of((typeof(ptr))READ_ONCE(ptr), type, member) |
69b90729 AK |
429 | |
430 | /** | |
431 | * list_for_each_entry_lockless - iterate over rcu list of given type | |
432 | * @pos: the type * to use as a loop cursor. | |
433 | * @head: the head for your list. | |
434 | * @member: the name of the list_struct within the struct. | |
435 | * | |
aff5f036 PM |
436 | * This primitive may safely run concurrently with the _rcu |
437 | * list-mutation primitives such as list_add_rcu(), but requires some | |
438 | * implicit RCU read-side guarding. One example is running within a special | |
439 | * exception-time environment where preemption is disabled and where lockdep | |
440 | * cannot be invoked. Another example is when items are added to the list, | |
441 | * but never deleted. | |
69b90729 AK |
442 | */ |
443 | #define list_for_each_entry_lockless(pos, head, member) \ | |
444 | for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \ | |
445 | &pos->member != (head); \ | |
446 | pos = list_entry_lockless(pos->member.next, typeof(*pos), member)) | |
447 | ||
254245d2 | 448 | /** |
449 | * list_for_each_entry_continue_rcu - continue iteration over list of given type | |
450 | * @pos: the type * to use as a loop cursor. | |
451 | * @head: the head for your list. | |
3943f42c | 452 | * @member: the name of the list_head within the struct. |
254245d2 | 453 | * |
454 | * Continue to iterate over list of given type, continuing after | |
b7b6f94c N |
455 | * the current position which must have been in the list when the RCU read |
456 | * lock was taken. | |
457 | * This would typically require either that you obtained the node from a | |
458 | * previous walk of the list in the same RCU read-side critical section, or | |
459 | * that you held some sort of non-RCU reference (such as a reference count) | |
460 | * to keep the node alive *and* in the list. | |
461 | * | |
462 | * This iterator is similar to list_for_each_entry_from_rcu() except | |
463 | * this starts after the given position and that one starts at the given | |
464 | * position. | |
254245d2 | 465 | */ |
466 | #define list_for_each_entry_continue_rcu(pos, head, member) \ | |
467 | for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \ | |
e66eed65 | 468 | &pos->member != (head); \ |
254245d2 | 469 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
470 | ||
ead9ad72 N |
471 | /** |
472 | * list_for_each_entry_from_rcu - iterate over a list from current point | |
473 | * @pos: the type * to use as a loop cursor. | |
474 | * @head: the head for your list. | |
475 | * @member: the name of the list_node within the struct. | |
476 | * | |
477 | * Iterate over the tail of a list starting from a given position, | |
478 | * which must have been in the list when the RCU read lock was taken. | |
b7b6f94c N |
479 | * This would typically require either that you obtained the node from a |
480 | * previous walk of the list in the same RCU read-side critical section, or | |
481 | * that you held some sort of non-RCU reference (such as a reference count) | |
482 | * to keep the node alive *and* in the list. | |
483 | * | |
484 | * This iterator is similar to list_for_each_entry_continue_rcu() except | |
485 | * this starts from the given position and that one starts from the position | |
486 | * after the given position. | |
ead9ad72 N |
487 | */ |
488 | #define list_for_each_entry_from_rcu(pos, head, member) \ | |
489 | for (; &(pos)->member != (head); \ | |
490 | pos = list_entry_rcu(pos->member.next, typeof(*(pos)), member)) | |
491 | ||
82524746 FBH |
492 | /** |
493 | * hlist_del_rcu - deletes entry from hash list without re-initialization | |
494 | * @n: the element to delete from the hash list. | |
495 | * | |
496 | * Note: list_unhashed() on entry does not return true after this, | |
497 | * the entry is in an undefined state. It is useful for RCU based | |
498 | * lockfree traversal. | |
499 | * | |
500 | * In particular, it means that we can not poison the forward | |
501 | * pointers that may still be used for walking the hash list. | |
502 | * | |
503 | * The caller must take whatever precautions are necessary | |
504 | * (such as holding appropriate locks) to avoid racing | |
505 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
506 | * or hlist_del_rcu(), running on this same list. | |
507 | * However, it is perfectly legal to run concurrently with | |
508 | * the _rcu list-traversal primitives, such as | |
509 | * hlist_for_each_entry(). | |
510 | */ | |
511 | static inline void hlist_del_rcu(struct hlist_node *n) | |
512 | { | |
513 | __hlist_del(n); | |
c54a2744 | 514 | WRITE_ONCE(n->pprev, LIST_POISON2); |
82524746 FBH |
515 | } |
516 | ||
517 | /** | |
518 | * hlist_replace_rcu - replace old entry by new one | |
519 | * @old : the element to be replaced | |
520 | * @new : the new element to insert | |
521 | * | |
522 | * The @old entry will be replaced with the @new entry atomically. | |
523 | */ | |
524 | static inline void hlist_replace_rcu(struct hlist_node *old, | |
525 | struct hlist_node *new) | |
526 | { | |
527 | struct hlist_node *next = old->next; | |
528 | ||
529 | new->next = next; | |
c54a2744 | 530 | WRITE_ONCE(new->pprev, old->pprev); |
67bdbffd | 531 | rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new); |
82524746 | 532 | if (next) |
c54a2744 ED |
533 | WRITE_ONCE(new->next->pprev, &new->next); |
534 | WRITE_ONCE(old->pprev, LIST_POISON2); | |
82524746 FBH |
535 | } |
536 | ||
35fc0e3b EB |
537 | /** |
538 | * hlists_swap_heads_rcu - swap the lists the hlist heads point to | |
539 | * @left: The hlist head on the left | |
540 | * @right: The hlist head on the right | |
541 | * | |
542 | * The lists start out as [@left ][node1 ... ] and | |
24692fa2 | 543 | * [@right ][node2 ... ] |
35fc0e3b EB |
544 | * The lists end up as [@left ][node2 ... ] |
545 | * [@right ][node1 ... ] | |
546 | */ | |
547 | static inline void hlists_swap_heads_rcu(struct hlist_head *left, struct hlist_head *right) | |
548 | { | |
549 | struct hlist_node *node1 = left->first; | |
550 | struct hlist_node *node2 = right->first; | |
551 | ||
552 | rcu_assign_pointer(left->first, node2); | |
553 | rcu_assign_pointer(right->first, node1); | |
554 | WRITE_ONCE(node2->pprev, &left->first); | |
555 | WRITE_ONCE(node1->pprev, &right->first); | |
556 | } | |
557 | ||
67bdbffd AB |
558 | /* |
559 | * return the first or the next element in an RCU protected hlist | |
560 | */ | |
561 | #define hlist_first_rcu(head) (*((struct hlist_node __rcu **)(&(head)->first))) | |
562 | #define hlist_next_rcu(node) (*((struct hlist_node __rcu **)(&(node)->next))) | |
563 | #define hlist_pprev_rcu(node) (*((struct hlist_node __rcu **)((node)->pprev))) | |
564 | ||
82524746 FBH |
565 | /** |
566 | * hlist_add_head_rcu | |
567 | * @n: the element to add to the hash list. | |
568 | * @h: the list to add to. | |
569 | * | |
570 | * Description: | |
571 | * Adds the specified element to the specified hlist, | |
572 | * while permitting racing traversals. | |
573 | * | |
574 | * The caller must take whatever precautions are necessary | |
575 | * (such as holding appropriate locks) to avoid racing | |
576 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
577 | * or hlist_del_rcu(), running on this same list. | |
578 | * However, it is perfectly legal to run concurrently with | |
579 | * the _rcu list-traversal primitives, such as | |
580 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
581 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
582 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
583 | */ | |
584 | static inline void hlist_add_head_rcu(struct hlist_node *n, | |
585 | struct hlist_head *h) | |
586 | { | |
587 | struct hlist_node *first = h->first; | |
10aa9d2c | 588 | |
82524746 | 589 | n->next = first; |
c54a2744 | 590 | WRITE_ONCE(n->pprev, &h->first); |
67bdbffd | 591 | rcu_assign_pointer(hlist_first_rcu(h), n); |
82524746 | 592 | if (first) |
c54a2744 | 593 | WRITE_ONCE(first->pprev, &n->next); |
82524746 FBH |
594 | } |
595 | ||
1602f49b DM |
596 | /** |
597 | * hlist_add_tail_rcu | |
598 | * @n: the element to add to the hash list. | |
599 | * @h: the list to add to. | |
600 | * | |
601 | * Description: | |
602 | * Adds the specified element to the specified hlist, | |
603 | * while permitting racing traversals. | |
604 | * | |
605 | * The caller must take whatever precautions are necessary | |
606 | * (such as holding appropriate locks) to avoid racing | |
607 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
608 | * or hlist_del_rcu(), running on this same list. | |
609 | * However, it is perfectly legal to run concurrently with | |
610 | * the _rcu list-traversal primitives, such as | |
611 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
612 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
613 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
614 | */ | |
615 | static inline void hlist_add_tail_rcu(struct hlist_node *n, | |
616 | struct hlist_head *h) | |
617 | { | |
618 | struct hlist_node *i, *last = NULL; | |
619 | ||
48ac3466 MT |
620 | /* Note: write side code, so rcu accessors are not needed. */ |
621 | for (i = h->first; i; i = i->next) | |
1602f49b DM |
622 | last = i; |
623 | ||
624 | if (last) { | |
625 | n->next = last->next; | |
c54a2744 | 626 | WRITE_ONCE(n->pprev, &last->next); |
1602f49b DM |
627 | rcu_assign_pointer(hlist_next_rcu(last), n); |
628 | } else { | |
629 | hlist_add_head_rcu(n, h); | |
630 | } | |
631 | } | |
632 | ||
82524746 FBH |
633 | /** |
634 | * hlist_add_before_rcu | |
635 | * @n: the new element to add to the hash list. | |
636 | * @next: the existing element to add the new element before. | |
637 | * | |
638 | * Description: | |
639 | * Adds the specified element to the specified hlist | |
640 | * before the specified node while permitting racing traversals. | |
641 | * | |
642 | * The caller must take whatever precautions are necessary | |
643 | * (such as holding appropriate locks) to avoid racing | |
644 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
645 | * or hlist_del_rcu(), running on this same list. | |
646 | * However, it is perfectly legal to run concurrently with | |
647 | * the _rcu list-traversal primitives, such as | |
648 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
649 | * problems on Alpha CPUs. | |
650 | */ | |
651 | static inline void hlist_add_before_rcu(struct hlist_node *n, | |
652 | struct hlist_node *next) | |
653 | { | |
c54a2744 | 654 | WRITE_ONCE(n->pprev, next->pprev); |
82524746 | 655 | n->next = next; |
67bdbffd | 656 | rcu_assign_pointer(hlist_pprev_rcu(n), n); |
c54a2744 | 657 | WRITE_ONCE(next->pprev, &n->next); |
82524746 FBH |
658 | } |
659 | ||
660 | /** | |
1d023284 | 661 | * hlist_add_behind_rcu |
82524746 | 662 | * @n: the new element to add to the hash list. |
1d023284 | 663 | * @prev: the existing element to add the new element after. |
82524746 FBH |
664 | * |
665 | * Description: | |
666 | * Adds the specified element to the specified hlist | |
667 | * after the specified node while permitting racing traversals. | |
668 | * | |
669 | * The caller must take whatever precautions are necessary | |
670 | * (such as holding appropriate locks) to avoid racing | |
671 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
672 | * or hlist_del_rcu(), running on this same list. | |
673 | * However, it is perfectly legal to run concurrently with | |
674 | * the _rcu list-traversal primitives, such as | |
675 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
676 | * problems on Alpha CPUs. | |
677 | */ | |
1d023284 KH |
678 | static inline void hlist_add_behind_rcu(struct hlist_node *n, |
679 | struct hlist_node *prev) | |
82524746 FBH |
680 | { |
681 | n->next = prev->next; | |
c54a2744 | 682 | WRITE_ONCE(n->pprev, &prev->next); |
67bdbffd | 683 | rcu_assign_pointer(hlist_next_rcu(prev), n); |
82524746 | 684 | if (n->next) |
c54a2744 | 685 | WRITE_ONCE(n->next->pprev, &n->next); |
82524746 FBH |
686 | } |
687 | ||
67bdbffd AB |
688 | #define __hlist_for_each_rcu(pos, head) \ |
689 | for (pos = rcu_dereference(hlist_first_rcu(head)); \ | |
75d65a42 | 690 | pos; \ |
67bdbffd | 691 | pos = rcu_dereference(hlist_next_rcu(pos))) |
1cc52327 | 692 | |
82524746 FBH |
693 | /** |
694 | * hlist_for_each_entry_rcu - iterate over rcu list of given type | |
b67bfe0d | 695 | * @pos: the type * to use as a loop cursor. |
82524746 FBH |
696 | * @head: the head for your list. |
697 | * @member: the name of the hlist_node within the struct. | |
ddc46593 | 698 | * @cond: optional lockdep expression if called from non-RCU protection. |
82524746 FBH |
699 | * |
700 | * This list-traversal primitive may safely run concurrently with | |
701 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
702 | * as long as the traversal is guarded by rcu_read_lock(). | |
703 | */ | |
28875945 JFG |
704 | #define hlist_for_each_entry_rcu(pos, head, member, cond...) \ |
705 | for (__list_check_rcu(dummy, ## cond, 0), \ | |
706 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\ | |
b67bfe0d SL |
707 | typeof(*(pos)), member); \ |
708 | pos; \ | |
709 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\ | |
ae2212a7 MB |
710 | &(pos)->member)), typeof(*(pos)), member)) |
711 | ||
712 | /** | |
713 | * hlist_for_each_entry_srcu - iterate over rcu list of given type | |
714 | * @pos: the type * to use as a loop cursor. | |
715 | * @head: the head for your list. | |
716 | * @member: the name of the hlist_node within the struct. | |
717 | * @cond: lockdep expression for the lock required to traverse the list. | |
718 | * | |
719 | * This list-traversal primitive may safely run concurrently with | |
720 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
721 | * as long as the traversal is guarded by srcu_read_lock(). | |
722 | * The lockdep expression srcu_read_lock_held() can be passed as the | |
723 | * cond argument from read side. | |
724 | */ | |
725 | #define hlist_for_each_entry_srcu(pos, head, member, cond) \ | |
726 | for (__list_check_srcu(cond), \ | |
727 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\ | |
728 | typeof(*(pos)), member); \ | |
729 | pos; \ | |
730 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\ | |
b67bfe0d | 731 | &(pos)->member)), typeof(*(pos)), member)) |
82524746 | 732 | |
12bcbe66 SR |
733 | /** |
734 | * hlist_for_each_entry_rcu_notrace - iterate over rcu list of given type (for tracing) | |
735 | * @pos: the type * to use as a loop cursor. | |
736 | * @head: the head for your list. | |
737 | * @member: the name of the hlist_node within the struct. | |
738 | * | |
739 | * This list-traversal primitive may safely run concurrently with | |
740 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
741 | * as long as the traversal is guarded by rcu_read_lock(). | |
742 | * | |
743 | * This is the same as hlist_for_each_entry_rcu() except that it does | |
744 | * not do any RCU debugging or tracing. | |
745 | */ | |
746 | #define hlist_for_each_entry_rcu_notrace(pos, head, member) \ | |
0a5b99f5 | 747 | for (pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_first_rcu(head)),\ |
12bcbe66 SR |
748 | typeof(*(pos)), member); \ |
749 | pos; \ | |
0a5b99f5 | 750 | pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_next_rcu(\ |
12bcbe66 SR |
751 | &(pos)->member)), typeof(*(pos)), member)) |
752 | ||
4f70ecca ED |
753 | /** |
754 | * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type | |
b67bfe0d | 755 | * @pos: the type * to use as a loop cursor. |
4f70ecca ED |
756 | * @head: the head for your list. |
757 | * @member: the name of the hlist_node within the struct. | |
758 | * | |
759 | * This list-traversal primitive may safely run concurrently with | |
760 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
761 | * as long as the traversal is guarded by rcu_read_lock(). | |
762 | */ | |
b67bfe0d SL |
763 | #define hlist_for_each_entry_rcu_bh(pos, head, member) \ |
764 | for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_first_rcu(head)),\ | |
765 | typeof(*(pos)), member); \ | |
766 | pos; \ | |
767 | pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(\ | |
768 | &(pos)->member)), typeof(*(pos)), member)) | |
4f70ecca | 769 | |
5c578aed | 770 | /** |
771 | * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point | |
b67bfe0d | 772 | * @pos: the type * to use as a loop cursor. |
5c578aed | 773 | * @member: the name of the hlist_node within the struct. |
774 | */ | |
b67bfe0d | 775 | #define hlist_for_each_entry_continue_rcu(pos, member) \ |
f520c98e YX |
776 | for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
777 | &(pos)->member)), typeof(*(pos)), member); \ | |
b67bfe0d | 778 | pos; \ |
f520c98e YX |
779 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
780 | &(pos)->member)), typeof(*(pos)), member)) | |
5c578aed | 781 | |
4f70ecca ED |
782 | /** |
783 | * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point | |
b67bfe0d | 784 | * @pos: the type * to use as a loop cursor. |
4f70ecca ED |
785 | * @member: the name of the hlist_node within the struct. |
786 | */ | |
b67bfe0d | 787 | #define hlist_for_each_entry_continue_rcu_bh(pos, member) \ |
f520c98e YX |
788 | for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \ |
789 | &(pos)->member)), typeof(*(pos)), member); \ | |
b67bfe0d | 790 | pos; \ |
f520c98e YX |
791 | pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu( \ |
792 | &(pos)->member)), typeof(*(pos)), member)) | |
4f70ecca | 793 | |
97ede29e YX |
794 | /** |
795 | * hlist_for_each_entry_from_rcu - iterate over a hlist continuing from current point | |
796 | * @pos: the type * to use as a loop cursor. | |
797 | * @member: the name of the hlist_node within the struct. | |
798 | */ | |
799 | #define hlist_for_each_entry_from_rcu(pos, member) \ | |
800 | for (; pos; \ | |
f517700c YX |
801 | pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \ |
802 | &(pos)->member)), typeof(*(pos)), member)) | |
5c578aed | 803 | |
82524746 FBH |
804 | #endif /* __KERNEL__ */ |
805 | #endif |