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82524746 FBH |
1 | #ifndef _LINUX_RCULIST_H |
2 | #define _LINUX_RCULIST_H | |
3 | ||
4 | #ifdef __KERNEL__ | |
5 | ||
6 | /* | |
7 | * RCU-protected list version | |
8 | */ | |
9 | #include <linux/list.h> | |
10aa9d2c | 10 | #include <linux/rcupdate.h> |
82524746 | 11 | |
65e6bf48 PM |
12 | /* |
13 | * Why is there no list_empty_rcu()? Because list_empty() serves this | |
14 | * purpose. The list_empty() function fetches the RCU-protected pointer | |
15 | * and compares it to the address of the list head, but neither dereferences | |
16 | * this pointer itself nor provides this pointer to the caller. Therefore, | |
17 | * it is not necessary to use rcu_dereference(), so that list_empty() can | |
18 | * be used anywhere you would want to use a list_empty_rcu(). | |
19 | */ | |
20 | ||
67bdbffd AB |
21 | /* |
22 | * return the ->next pointer of a list_head in an rcu safe | |
23 | * way, we must not access it directly | |
24 | */ | |
25 | #define list_next_rcu(list) (*((struct list_head __rcu **)(&(list)->next))) | |
26 | ||
82524746 FBH |
27 | /* |
28 | * Insert a new entry between two known consecutive entries. | |
29 | * | |
30 | * This is only for internal list manipulation where we know | |
31 | * the prev/next entries already! | |
32 | */ | |
559f9bad | 33 | #ifndef CONFIG_DEBUG_LIST |
82524746 FBH |
34 | static inline void __list_add_rcu(struct list_head *new, |
35 | struct list_head *prev, struct list_head *next) | |
36 | { | |
37 | new->next = next; | |
38 | new->prev = prev; | |
67bdbffd | 39 | rcu_assign_pointer(list_next_rcu(prev), new); |
82524746 | 40 | next->prev = new; |
82524746 | 41 | } |
559f9bad DJ |
42 | #else |
43 | extern void __list_add_rcu(struct list_head *new, | |
44 | struct list_head *prev, struct list_head *next); | |
45 | #endif | |
82524746 FBH |
46 | |
47 | /** | |
48 | * list_add_rcu - add a new entry to rcu-protected list | |
49 | * @new: new entry to be added | |
50 | * @head: list head to add it after | |
51 | * | |
52 | * Insert a new entry after the specified head. | |
53 | * This is good for implementing stacks. | |
54 | * | |
55 | * The caller must take whatever precautions are necessary | |
56 | * (such as holding appropriate locks) to avoid racing | |
57 | * with another list-mutation primitive, such as list_add_rcu() | |
58 | * or list_del_rcu(), running on this same list. | |
59 | * However, it is perfectly legal to run concurrently with | |
60 | * the _rcu list-traversal primitives, such as | |
61 | * list_for_each_entry_rcu(). | |
62 | */ | |
63 | static inline void list_add_rcu(struct list_head *new, struct list_head *head) | |
64 | { | |
65 | __list_add_rcu(new, head, head->next); | |
66 | } | |
67 | ||
68 | /** | |
69 | * list_add_tail_rcu - add a new entry to rcu-protected list | |
70 | * @new: new entry to be added | |
71 | * @head: list head to add it before | |
72 | * | |
73 | * Insert a new entry before the specified head. | |
74 | * This is useful for implementing queues. | |
75 | * | |
76 | * The caller must take whatever precautions are necessary | |
77 | * (such as holding appropriate locks) to avoid racing | |
78 | * with another list-mutation primitive, such as list_add_tail_rcu() | |
79 | * or list_del_rcu(), running on this same list. | |
80 | * However, it is perfectly legal to run concurrently with | |
81 | * the _rcu list-traversal primitives, such as | |
82 | * list_for_each_entry_rcu(). | |
83 | */ | |
84 | static inline void list_add_tail_rcu(struct list_head *new, | |
85 | struct list_head *head) | |
86 | { | |
87 | __list_add_rcu(new, head->prev, head); | |
88 | } | |
89 | ||
90 | /** | |
91 | * list_del_rcu - deletes entry from list without re-initialization | |
92 | * @entry: the element to delete from the list. | |
93 | * | |
94 | * Note: list_empty() on entry does not return true after this, | |
95 | * the entry is in an undefined state. It is useful for RCU based | |
96 | * lockfree traversal. | |
97 | * | |
98 | * In particular, it means that we can not poison the forward | |
99 | * pointers that may still be used for walking the list. | |
100 | * | |
101 | * The caller must take whatever precautions are necessary | |
102 | * (such as holding appropriate locks) to avoid racing | |
103 | * with another list-mutation primitive, such as list_del_rcu() | |
104 | * or list_add_rcu(), running on this same list. | |
105 | * However, it is perfectly legal to run concurrently with | |
106 | * the _rcu list-traversal primitives, such as | |
107 | * list_for_each_entry_rcu(). | |
108 | * | |
109 | * Note that the caller is not permitted to immediately free | |
110 | * the newly deleted entry. Instead, either synchronize_rcu() | |
111 | * or call_rcu() must be used to defer freeing until an RCU | |
112 | * grace period has elapsed. | |
113 | */ | |
114 | static inline void list_del_rcu(struct list_head *entry) | |
115 | { | |
559f9bad | 116 | __list_del_entry(entry); |
82524746 FBH |
117 | entry->prev = LIST_POISON2; |
118 | } | |
119 | ||
6beeac76 AA |
120 | /** |
121 | * hlist_del_init_rcu - deletes entry from hash list with re-initialization | |
122 | * @n: the element to delete from the hash list. | |
123 | * | |
124 | * Note: list_unhashed() on the node return true after this. It is | |
125 | * useful for RCU based read lockfree traversal if the writer side | |
126 | * must know if the list entry is still hashed or already unhashed. | |
127 | * | |
128 | * In particular, it means that we can not poison the forward pointers | |
129 | * that may still be used for walking the hash list and we can only | |
130 | * zero the pprev pointer so list_unhashed() will return true after | |
131 | * this. | |
132 | * | |
133 | * The caller must take whatever precautions are necessary (such as | |
134 | * holding appropriate locks) to avoid racing with another | |
135 | * list-mutation primitive, such as hlist_add_head_rcu() or | |
136 | * hlist_del_rcu(), running on this same list. However, it is | |
137 | * perfectly legal to run concurrently with the _rcu list-traversal | |
138 | * primitives, such as hlist_for_each_entry_rcu(). | |
139 | */ | |
140 | static inline void hlist_del_init_rcu(struct hlist_node *n) | |
141 | { | |
142 | if (!hlist_unhashed(n)) { | |
143 | __hlist_del(n); | |
144 | n->pprev = NULL; | |
145 | } | |
146 | } | |
147 | ||
82524746 FBH |
148 | /** |
149 | * list_replace_rcu - replace old entry by new one | |
150 | * @old : the element to be replaced | |
151 | * @new : the new element to insert | |
152 | * | |
153 | * The @old entry will be replaced with the @new entry atomically. | |
154 | * Note: @old should not be empty. | |
155 | */ | |
156 | static inline void list_replace_rcu(struct list_head *old, | |
157 | struct list_head *new) | |
158 | { | |
159 | new->next = old->next; | |
160 | new->prev = old->prev; | |
67bdbffd | 161 | rcu_assign_pointer(list_next_rcu(new->prev), new); |
82524746 | 162 | new->next->prev = new; |
82524746 FBH |
163 | old->prev = LIST_POISON2; |
164 | } | |
165 | ||
166 | /** | |
167 | * list_splice_init_rcu - splice an RCU-protected list into an existing list. | |
168 | * @list: the RCU-protected list to splice | |
169 | * @head: the place in the list to splice the first list into | |
170 | * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ... | |
171 | * | |
172 | * @head can be RCU-read traversed concurrently with this function. | |
173 | * | |
174 | * Note that this function blocks. | |
175 | * | |
176 | * Important note: the caller must take whatever action is necessary to | |
177 | * prevent any other updates to @head. In principle, it is possible | |
178 | * to modify the list as soon as sync() begins execution. | |
179 | * If this sort of thing becomes necessary, an alternative version | |
180 | * based on call_rcu() could be created. But only if -really- | |
181 | * needed -- there is no shortage of RCU API members. | |
182 | */ | |
183 | static inline void list_splice_init_rcu(struct list_head *list, | |
184 | struct list_head *head, | |
185 | void (*sync)(void)) | |
186 | { | |
187 | struct list_head *first = list->next; | |
188 | struct list_head *last = list->prev; | |
189 | struct list_head *at = head->next; | |
190 | ||
7f708931 | 191 | if (list_empty(list)) |
82524746 FBH |
192 | return; |
193 | ||
194 | /* "first" and "last" tracking list, so initialize it. */ | |
195 | ||
196 | INIT_LIST_HEAD(list); | |
197 | ||
198 | /* | |
199 | * At this point, the list body still points to the source list. | |
200 | * Wait for any readers to finish using the list before splicing | |
201 | * the list body into the new list. Any new readers will see | |
202 | * an empty list. | |
203 | */ | |
204 | ||
205 | sync(); | |
206 | ||
207 | /* | |
208 | * Readers are finished with the source list, so perform splice. | |
209 | * The order is important if the new list is global and accessible | |
210 | * to concurrent RCU readers. Note that RCU readers are not | |
211 | * permitted to traverse the prev pointers without excluding | |
212 | * this function. | |
213 | */ | |
214 | ||
215 | last->next = at; | |
67bdbffd | 216 | rcu_assign_pointer(list_next_rcu(head), first); |
82524746 FBH |
217 | first->prev = head; |
218 | at->prev = last; | |
219 | } | |
220 | ||
72c6a987 JP |
221 | /** |
222 | * list_entry_rcu - get the struct for this entry | |
223 | * @ptr: the &struct list_head pointer. | |
224 | * @type: the type of the struct this is embedded in. | |
225 | * @member: the name of the list_struct within the struct. | |
226 | * | |
227 | * This primitive may safely run concurrently with the _rcu list-mutation | |
228 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). | |
229 | */ | |
230 | #define list_entry_rcu(ptr, type, member) \ | |
67bdbffd AB |
231 | ({typeof (*ptr) __rcu *__ptr = (typeof (*ptr) __rcu __force *)ptr; \ |
232 | container_of((typeof(ptr))rcu_dereference_raw(__ptr), type, member); \ | |
233 | }) | |
72c6a987 JP |
234 | |
235 | /** | |
236 | * list_first_entry_rcu - get the first element from a list | |
237 | * @ptr: the list head to take the element from. | |
238 | * @type: the type of the struct this is embedded in. | |
239 | * @member: the name of the list_struct within the struct. | |
240 | * | |
241 | * Note, that list is expected to be not empty. | |
242 | * | |
243 | * This primitive may safely run concurrently with the _rcu list-mutation | |
244 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). | |
245 | */ | |
246 | #define list_first_entry_rcu(ptr, type, member) \ | |
247 | list_entry_rcu((ptr)->next, type, member) | |
248 | ||
82524746 FBH |
249 | /** |
250 | * list_for_each_entry_rcu - iterate over rcu list of given type | |
251 | * @pos: the type * to use as a loop cursor. | |
252 | * @head: the head for your list. | |
253 | * @member: the name of the list_struct within the struct. | |
254 | * | |
255 | * This list-traversal primitive may safely run concurrently with | |
256 | * the _rcu list-mutation primitives such as list_add_rcu() | |
257 | * as long as the traversal is guarded by rcu_read_lock(). | |
258 | */ | |
259 | #define list_for_each_entry_rcu(pos, head, member) \ | |
72c6a987 | 260 | for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \ |
e66eed65 | 261 | &pos->member != (head); \ |
72c6a987 | 262 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
82524746 FBH |
263 | |
264 | ||
265 | /** | |
266 | * list_for_each_continue_rcu | |
267 | * @pos: the &struct list_head to use as a loop cursor. | |
268 | * @head: the head for your list. | |
269 | * | |
270 | * Iterate over an rcu-protected list, continuing after current point. | |
271 | * | |
272 | * This list-traversal primitive may safely run concurrently with | |
273 | * the _rcu list-mutation primitives such as list_add_rcu() | |
274 | * as long as the traversal is guarded by rcu_read_lock(). | |
275 | */ | |
276 | #define list_for_each_continue_rcu(pos, head) \ | |
67bdbffd | 277 | for ((pos) = rcu_dereference_raw(list_next_rcu(pos)); \ |
e66eed65 | 278 | (pos) != (head); \ |
67bdbffd | 279 | (pos) = rcu_dereference_raw(list_next_rcu(pos))) |
82524746 | 280 | |
254245d2 | 281 | /** |
282 | * list_for_each_entry_continue_rcu - continue iteration over list of given type | |
283 | * @pos: the type * to use as a loop cursor. | |
284 | * @head: the head for your list. | |
285 | * @member: the name of the list_struct within the struct. | |
286 | * | |
287 | * Continue to iterate over list of given type, continuing after | |
288 | * the current position. | |
289 | */ | |
290 | #define list_for_each_entry_continue_rcu(pos, head, member) \ | |
291 | for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \ | |
e66eed65 | 292 | &pos->member != (head); \ |
254245d2 | 293 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
294 | ||
82524746 FBH |
295 | /** |
296 | * hlist_del_rcu - deletes entry from hash list without re-initialization | |
297 | * @n: the element to delete from the hash list. | |
298 | * | |
299 | * Note: list_unhashed() on entry does not return true after this, | |
300 | * the entry is in an undefined state. It is useful for RCU based | |
301 | * lockfree traversal. | |
302 | * | |
303 | * In particular, it means that we can not poison the forward | |
304 | * pointers that may still be used for walking the hash list. | |
305 | * | |
306 | * The caller must take whatever precautions are necessary | |
307 | * (such as holding appropriate locks) to avoid racing | |
308 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
309 | * or hlist_del_rcu(), running on this same list. | |
310 | * However, it is perfectly legal to run concurrently with | |
311 | * the _rcu list-traversal primitives, such as | |
312 | * hlist_for_each_entry(). | |
313 | */ | |
314 | static inline void hlist_del_rcu(struct hlist_node *n) | |
315 | { | |
316 | __hlist_del(n); | |
317 | n->pprev = LIST_POISON2; | |
318 | } | |
319 | ||
320 | /** | |
321 | * hlist_replace_rcu - replace old entry by new one | |
322 | * @old : the element to be replaced | |
323 | * @new : the new element to insert | |
324 | * | |
325 | * The @old entry will be replaced with the @new entry atomically. | |
326 | */ | |
327 | static inline void hlist_replace_rcu(struct hlist_node *old, | |
328 | struct hlist_node *new) | |
329 | { | |
330 | struct hlist_node *next = old->next; | |
331 | ||
332 | new->next = next; | |
333 | new->pprev = old->pprev; | |
67bdbffd | 334 | rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new); |
82524746 FBH |
335 | if (next) |
336 | new->next->pprev = &new->next; | |
82524746 FBH |
337 | old->pprev = LIST_POISON2; |
338 | } | |
339 | ||
67bdbffd AB |
340 | /* |
341 | * return the first or the next element in an RCU protected hlist | |
342 | */ | |
343 | #define hlist_first_rcu(head) (*((struct hlist_node __rcu **)(&(head)->first))) | |
344 | #define hlist_next_rcu(node) (*((struct hlist_node __rcu **)(&(node)->next))) | |
345 | #define hlist_pprev_rcu(node) (*((struct hlist_node __rcu **)((node)->pprev))) | |
346 | ||
82524746 FBH |
347 | /** |
348 | * hlist_add_head_rcu | |
349 | * @n: the element to add to the hash list. | |
350 | * @h: the list to add to. | |
351 | * | |
352 | * Description: | |
353 | * Adds the specified element to the specified hlist, | |
354 | * while permitting racing traversals. | |
355 | * | |
356 | * The caller must take whatever precautions are necessary | |
357 | * (such as holding appropriate locks) to avoid racing | |
358 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
359 | * or hlist_del_rcu(), running on this same list. | |
360 | * However, it is perfectly legal to run concurrently with | |
361 | * the _rcu list-traversal primitives, such as | |
362 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
363 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
364 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
365 | */ | |
366 | static inline void hlist_add_head_rcu(struct hlist_node *n, | |
367 | struct hlist_head *h) | |
368 | { | |
369 | struct hlist_node *first = h->first; | |
10aa9d2c | 370 | |
82524746 FBH |
371 | n->next = first; |
372 | n->pprev = &h->first; | |
67bdbffd | 373 | rcu_assign_pointer(hlist_first_rcu(h), n); |
82524746 FBH |
374 | if (first) |
375 | first->pprev = &n->next; | |
82524746 FBH |
376 | } |
377 | ||
378 | /** | |
379 | * hlist_add_before_rcu | |
380 | * @n: the new element to add to the hash list. | |
381 | * @next: the existing element to add the new element before. | |
382 | * | |
383 | * Description: | |
384 | * Adds the specified element to the specified hlist | |
385 | * before the specified node while permitting racing traversals. | |
386 | * | |
387 | * The caller must take whatever precautions are necessary | |
388 | * (such as holding appropriate locks) to avoid racing | |
389 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
390 | * or hlist_del_rcu(), running on this same list. | |
391 | * However, it is perfectly legal to run concurrently with | |
392 | * the _rcu list-traversal primitives, such as | |
393 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
394 | * problems on Alpha CPUs. | |
395 | */ | |
396 | static inline void hlist_add_before_rcu(struct hlist_node *n, | |
397 | struct hlist_node *next) | |
398 | { | |
399 | n->pprev = next->pprev; | |
400 | n->next = next; | |
67bdbffd | 401 | rcu_assign_pointer(hlist_pprev_rcu(n), n); |
82524746 | 402 | next->pprev = &n->next; |
82524746 FBH |
403 | } |
404 | ||
405 | /** | |
406 | * hlist_add_after_rcu | |
407 | * @prev: the existing element to add the new element after. | |
408 | * @n: the new element to add to the hash list. | |
409 | * | |
410 | * Description: | |
411 | * Adds the specified element to the specified hlist | |
412 | * after the specified node while permitting racing traversals. | |
413 | * | |
414 | * The caller must take whatever precautions are necessary | |
415 | * (such as holding appropriate locks) to avoid racing | |
416 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
417 | * or hlist_del_rcu(), running on this same list. | |
418 | * However, it is perfectly legal to run concurrently with | |
419 | * the _rcu list-traversal primitives, such as | |
420 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
421 | * problems on Alpha CPUs. | |
422 | */ | |
423 | static inline void hlist_add_after_rcu(struct hlist_node *prev, | |
424 | struct hlist_node *n) | |
425 | { | |
426 | n->next = prev->next; | |
427 | n->pprev = &prev->next; | |
67bdbffd | 428 | rcu_assign_pointer(hlist_next_rcu(prev), n); |
82524746 FBH |
429 | if (n->next) |
430 | n->next->pprev = &n->next; | |
431 | } | |
432 | ||
67bdbffd AB |
433 | #define __hlist_for_each_rcu(pos, head) \ |
434 | for (pos = rcu_dereference(hlist_first_rcu(head)); \ | |
75d65a42 | 435 | pos; \ |
67bdbffd | 436 | pos = rcu_dereference(hlist_next_rcu(pos))) |
1cc52327 | 437 | |
82524746 FBH |
438 | /** |
439 | * hlist_for_each_entry_rcu - iterate over rcu list of given type | |
440 | * @tpos: the type * to use as a loop cursor. | |
441 | * @pos: the &struct hlist_node to use as a loop cursor. | |
442 | * @head: the head for your list. | |
443 | * @member: the name of the hlist_node within the struct. | |
444 | * | |
445 | * This list-traversal primitive may safely run concurrently with | |
446 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
447 | * as long as the traversal is guarded by rcu_read_lock(). | |
448 | */ | |
67bdbffd AB |
449 | #define hlist_for_each_entry_rcu(tpos, pos, head, member) \ |
450 | for (pos = rcu_dereference_raw(hlist_first_rcu(head)); \ | |
75d65a42 | 451 | pos && \ |
82524746 | 452 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
67bdbffd | 453 | pos = rcu_dereference_raw(hlist_next_rcu(pos))) |
82524746 | 454 | |
4f70ecca ED |
455 | /** |
456 | * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type | |
457 | * @tpos: the type * to use as a loop cursor. | |
458 | * @pos: the &struct hlist_node to use as a loop cursor. | |
459 | * @head: the head for your list. | |
460 | * @member: the name of the hlist_node within the struct. | |
461 | * | |
462 | * This list-traversal primitive may safely run concurrently with | |
463 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
464 | * as long as the traversal is guarded by rcu_read_lock(). | |
465 | */ | |
466 | #define hlist_for_each_entry_rcu_bh(tpos, pos, head, member) \ | |
467 | for (pos = rcu_dereference_bh((head)->first); \ | |
75d65a42 | 468 | pos && \ |
4f70ecca ED |
469 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
470 | pos = rcu_dereference_bh(pos->next)) | |
471 | ||
5c578aed | 472 | /** |
473 | * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point | |
474 | * @tpos: the type * to use as a loop cursor. | |
475 | * @pos: the &struct hlist_node to use as a loop cursor. | |
476 | * @member: the name of the hlist_node within the struct. | |
477 | */ | |
478 | #define hlist_for_each_entry_continue_rcu(tpos, pos, member) \ | |
479 | for (pos = rcu_dereference((pos)->next); \ | |
75d65a42 | 480 | pos && \ |
5c578aed | 481 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
482 | pos = rcu_dereference(pos->next)) | |
483 | ||
4f70ecca ED |
484 | /** |
485 | * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point | |
486 | * @tpos: the type * to use as a loop cursor. | |
487 | * @pos: the &struct hlist_node to use as a loop cursor. | |
488 | * @member: the name of the hlist_node within the struct. | |
489 | */ | |
490 | #define hlist_for_each_entry_continue_rcu_bh(tpos, pos, member) \ | |
491 | for (pos = rcu_dereference_bh((pos)->next); \ | |
75d65a42 | 492 | pos && \ |
4f70ecca ED |
493 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
494 | pos = rcu_dereference_bh(pos->next)) | |
495 | ||
5c578aed | 496 | |
82524746 FBH |
497 | #endif /* __KERNEL__ */ |
498 | #endif |