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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 | */ | |
33 | static inline void __list_add_rcu(struct list_head *new, | |
34 | struct list_head *prev, struct list_head *next) | |
35 | { | |
36 | new->next = next; | |
37 | new->prev = prev; | |
67bdbffd | 38 | rcu_assign_pointer(list_next_rcu(prev), new); |
82524746 | 39 | next->prev = new; |
82524746 FBH |
40 | } |
41 | ||
42 | /** | |
43 | * list_add_rcu - add a new entry to rcu-protected list | |
44 | * @new: new entry to be added | |
45 | * @head: list head to add it after | |
46 | * | |
47 | * Insert a new entry after the specified head. | |
48 | * This is good for implementing stacks. | |
49 | * | |
50 | * The caller must take whatever precautions are necessary | |
51 | * (such as holding appropriate locks) to avoid racing | |
52 | * with another list-mutation primitive, such as list_add_rcu() | |
53 | * or list_del_rcu(), running on this same list. | |
54 | * However, it is perfectly legal to run concurrently with | |
55 | * the _rcu list-traversal primitives, such as | |
56 | * list_for_each_entry_rcu(). | |
57 | */ | |
58 | static inline void list_add_rcu(struct list_head *new, struct list_head *head) | |
59 | { | |
60 | __list_add_rcu(new, head, head->next); | |
61 | } | |
62 | ||
63 | /** | |
64 | * list_add_tail_rcu - add a new entry to rcu-protected list | |
65 | * @new: new entry to be added | |
66 | * @head: list head to add it before | |
67 | * | |
68 | * Insert a new entry before the specified head. | |
69 | * This is useful for implementing queues. | |
70 | * | |
71 | * The caller must take whatever precautions are necessary | |
72 | * (such as holding appropriate locks) to avoid racing | |
73 | * with another list-mutation primitive, such as list_add_tail_rcu() | |
74 | * or list_del_rcu(), running on this same list. | |
75 | * However, it is perfectly legal to run concurrently with | |
76 | * the _rcu list-traversal primitives, such as | |
77 | * list_for_each_entry_rcu(). | |
78 | */ | |
79 | static inline void list_add_tail_rcu(struct list_head *new, | |
80 | struct list_head *head) | |
81 | { | |
82 | __list_add_rcu(new, head->prev, head); | |
83 | } | |
84 | ||
85 | /** | |
86 | * list_del_rcu - deletes entry from list without re-initialization | |
87 | * @entry: the element to delete from the list. | |
88 | * | |
89 | * Note: list_empty() on entry does not return true after this, | |
90 | * the entry is in an undefined state. It is useful for RCU based | |
91 | * lockfree traversal. | |
92 | * | |
93 | * In particular, it means that we can not poison the forward | |
94 | * pointers that may still be used for walking the list. | |
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_del_rcu() | |
99 | * or list_add_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 | * Note that the caller is not permitted to immediately free | |
105 | * the newly deleted entry. Instead, either synchronize_rcu() | |
106 | * or call_rcu() must be used to defer freeing until an RCU | |
107 | * grace period has elapsed. | |
108 | */ | |
109 | static inline void list_del_rcu(struct list_head *entry) | |
110 | { | |
111 | __list_del(entry->prev, entry->next); | |
112 | entry->prev = LIST_POISON2; | |
113 | } | |
114 | ||
6beeac76 AA |
115 | /** |
116 | * hlist_del_init_rcu - deletes entry from hash list with re-initialization | |
117 | * @n: the element to delete from the hash list. | |
118 | * | |
119 | * Note: list_unhashed() on the node return true after this. It is | |
120 | * useful for RCU based read lockfree traversal if the writer side | |
121 | * must know if the list entry is still hashed or already unhashed. | |
122 | * | |
123 | * In particular, it means that we can not poison the forward pointers | |
124 | * that may still be used for walking the hash list and we can only | |
125 | * zero the pprev pointer so list_unhashed() will return true after | |
126 | * this. | |
127 | * | |
128 | * The caller must take whatever precautions are necessary (such as | |
129 | * holding appropriate locks) to avoid racing with another | |
130 | * list-mutation primitive, such as hlist_add_head_rcu() or | |
131 | * hlist_del_rcu(), running on this same list. However, it is | |
132 | * perfectly legal to run concurrently with the _rcu list-traversal | |
133 | * primitives, such as hlist_for_each_entry_rcu(). | |
134 | */ | |
135 | static inline void hlist_del_init_rcu(struct hlist_node *n) | |
136 | { | |
137 | if (!hlist_unhashed(n)) { | |
138 | __hlist_del(n); | |
139 | n->pprev = NULL; | |
140 | } | |
141 | } | |
142 | ||
82524746 FBH |
143 | /** |
144 | * list_replace_rcu - replace old entry by new one | |
145 | * @old : the element to be replaced | |
146 | * @new : the new element to insert | |
147 | * | |
148 | * The @old entry will be replaced with the @new entry atomically. | |
149 | * Note: @old should not be empty. | |
150 | */ | |
151 | static inline void list_replace_rcu(struct list_head *old, | |
152 | struct list_head *new) | |
153 | { | |
154 | new->next = old->next; | |
155 | new->prev = old->prev; | |
67bdbffd | 156 | rcu_assign_pointer(list_next_rcu(new->prev), new); |
82524746 | 157 | new->next->prev = new; |
82524746 FBH |
158 | old->prev = LIST_POISON2; |
159 | } | |
160 | ||
161 | /** | |
162 | * list_splice_init_rcu - splice an RCU-protected list into an existing list. | |
163 | * @list: the RCU-protected list to splice | |
164 | * @head: the place in the list to splice the first list into | |
165 | * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ... | |
166 | * | |
167 | * @head can be RCU-read traversed concurrently with this function. | |
168 | * | |
169 | * Note that this function blocks. | |
170 | * | |
171 | * Important note: the caller must take whatever action is necessary to | |
172 | * prevent any other updates to @head. In principle, it is possible | |
173 | * to modify the list as soon as sync() begins execution. | |
174 | * If this sort of thing becomes necessary, an alternative version | |
175 | * based on call_rcu() could be created. But only if -really- | |
176 | * needed -- there is no shortage of RCU API members. | |
177 | */ | |
178 | static inline void list_splice_init_rcu(struct list_head *list, | |
179 | struct list_head *head, | |
180 | void (*sync)(void)) | |
181 | { | |
182 | struct list_head *first = list->next; | |
183 | struct list_head *last = list->prev; | |
184 | struct list_head *at = head->next; | |
185 | ||
186 | if (list_empty(head)) | |
187 | return; | |
188 | ||
189 | /* "first" and "last" tracking list, so initialize it. */ | |
190 | ||
191 | INIT_LIST_HEAD(list); | |
192 | ||
193 | /* | |
194 | * At this point, the list body still points to the source list. | |
195 | * Wait for any readers to finish using the list before splicing | |
196 | * the list body into the new list. Any new readers will see | |
197 | * an empty list. | |
198 | */ | |
199 | ||
200 | sync(); | |
201 | ||
202 | /* | |
203 | * Readers are finished with the source list, so perform splice. | |
204 | * The order is important if the new list is global and accessible | |
205 | * to concurrent RCU readers. Note that RCU readers are not | |
206 | * permitted to traverse the prev pointers without excluding | |
207 | * this function. | |
208 | */ | |
209 | ||
210 | last->next = at; | |
67bdbffd | 211 | rcu_assign_pointer(list_next_rcu(head), first); |
82524746 FBH |
212 | first->prev = head; |
213 | at->prev = last; | |
214 | } | |
215 | ||
72c6a987 JP |
216 | /** |
217 | * list_entry_rcu - get the struct for this entry | |
218 | * @ptr: the &struct list_head pointer. | |
219 | * @type: the type of the struct this is embedded in. | |
220 | * @member: the name of the list_struct within the struct. | |
221 | * | |
222 | * This primitive may safely run concurrently with the _rcu list-mutation | |
223 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). | |
224 | */ | |
225 | #define list_entry_rcu(ptr, type, member) \ | |
67bdbffd AB |
226 | ({typeof (*ptr) __rcu *__ptr = (typeof (*ptr) __rcu __force *)ptr; \ |
227 | container_of((typeof(ptr))rcu_dereference_raw(__ptr), type, member); \ | |
228 | }) | |
72c6a987 JP |
229 | |
230 | /** | |
231 | * list_first_entry_rcu - get the first element from a list | |
232 | * @ptr: the list head to take the element from. | |
233 | * @type: the type of the struct this is embedded in. | |
234 | * @member: the name of the list_struct within the struct. | |
235 | * | |
236 | * Note, that list is expected to be not empty. | |
237 | * | |
238 | * This primitive may safely run concurrently with the _rcu list-mutation | |
239 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). | |
240 | */ | |
241 | #define list_first_entry_rcu(ptr, type, member) \ | |
242 | list_entry_rcu((ptr)->next, type, member) | |
243 | ||
82524746 FBH |
244 | /** |
245 | * list_for_each_entry_rcu - iterate over rcu list of given type | |
246 | * @pos: the type * to use as a loop cursor. | |
247 | * @head: the head for your list. | |
248 | * @member: the name of the list_struct within the struct. | |
249 | * | |
250 | * This list-traversal primitive may safely run concurrently with | |
251 | * the _rcu list-mutation primitives such as list_add_rcu() | |
252 | * as long as the traversal is guarded by rcu_read_lock(). | |
253 | */ | |
254 | #define list_for_each_entry_rcu(pos, head, member) \ | |
72c6a987 | 255 | for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \ |
78b0e0e9 | 256 | prefetch(pos->member.next), &pos->member != (head); \ |
72c6a987 | 257 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
82524746 FBH |
258 | |
259 | ||
260 | /** | |
261 | * list_for_each_continue_rcu | |
262 | * @pos: the &struct list_head to use as a loop cursor. | |
263 | * @head: the head for your list. | |
264 | * | |
265 | * Iterate over an rcu-protected list, continuing after current point. | |
266 | * | |
267 | * This list-traversal primitive may safely run concurrently with | |
268 | * the _rcu list-mutation primitives such as list_add_rcu() | |
269 | * as long as the traversal is guarded by rcu_read_lock(). | |
270 | */ | |
271 | #define list_for_each_continue_rcu(pos, head) \ | |
67bdbffd | 272 | for ((pos) = rcu_dereference_raw(list_next_rcu(pos)); \ |
78b0e0e9 | 273 | prefetch((pos)->next), (pos) != (head); \ |
67bdbffd | 274 | (pos) = rcu_dereference_raw(list_next_rcu(pos))) |
82524746 | 275 | |
254245d2 | 276 | /** |
277 | * list_for_each_entry_continue_rcu - continue iteration over list of given type | |
278 | * @pos: the type * to use as a loop cursor. | |
279 | * @head: the head for your list. | |
280 | * @member: the name of the list_struct within the struct. | |
281 | * | |
282 | * Continue to iterate over list of given type, continuing after | |
283 | * the current position. | |
284 | */ | |
285 | #define list_for_each_entry_continue_rcu(pos, head, member) \ | |
286 | for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \ | |
287 | prefetch(pos->member.next), &pos->member != (head); \ | |
288 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) | |
289 | ||
82524746 FBH |
290 | /** |
291 | * hlist_del_rcu - deletes entry from hash list without re-initialization | |
292 | * @n: the element to delete from the hash list. | |
293 | * | |
294 | * Note: list_unhashed() on entry does not return true after this, | |
295 | * the entry is in an undefined state. It is useful for RCU based | |
296 | * lockfree traversal. | |
297 | * | |
298 | * In particular, it means that we can not poison the forward | |
299 | * pointers that may still be used for walking the hash list. | |
300 | * | |
301 | * The caller must take whatever precautions are necessary | |
302 | * (such as holding appropriate locks) to avoid racing | |
303 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
304 | * or hlist_del_rcu(), running on this same list. | |
305 | * However, it is perfectly legal to run concurrently with | |
306 | * the _rcu list-traversal primitives, such as | |
307 | * hlist_for_each_entry(). | |
308 | */ | |
309 | static inline void hlist_del_rcu(struct hlist_node *n) | |
310 | { | |
311 | __hlist_del(n); | |
312 | n->pprev = LIST_POISON2; | |
313 | } | |
314 | ||
315 | /** | |
316 | * hlist_replace_rcu - replace old entry by new one | |
317 | * @old : the element to be replaced | |
318 | * @new : the new element to insert | |
319 | * | |
320 | * The @old entry will be replaced with the @new entry atomically. | |
321 | */ | |
322 | static inline void hlist_replace_rcu(struct hlist_node *old, | |
323 | struct hlist_node *new) | |
324 | { | |
325 | struct hlist_node *next = old->next; | |
326 | ||
327 | new->next = next; | |
328 | new->pprev = old->pprev; | |
67bdbffd | 329 | rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new); |
82524746 FBH |
330 | if (next) |
331 | new->next->pprev = &new->next; | |
82524746 FBH |
332 | old->pprev = LIST_POISON2; |
333 | } | |
334 | ||
67bdbffd AB |
335 | /* |
336 | * return the first or the next element in an RCU protected hlist | |
337 | */ | |
338 | #define hlist_first_rcu(head) (*((struct hlist_node __rcu **)(&(head)->first))) | |
339 | #define hlist_next_rcu(node) (*((struct hlist_node __rcu **)(&(node)->next))) | |
340 | #define hlist_pprev_rcu(node) (*((struct hlist_node __rcu **)((node)->pprev))) | |
341 | ||
82524746 FBH |
342 | /** |
343 | * hlist_add_head_rcu | |
344 | * @n: the element to add to the hash list. | |
345 | * @h: the list to add to. | |
346 | * | |
347 | * Description: | |
348 | * Adds the specified element to the specified hlist, | |
349 | * while permitting racing traversals. | |
350 | * | |
351 | * The caller must take whatever precautions are necessary | |
352 | * (such as holding appropriate locks) to avoid racing | |
353 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
354 | * or hlist_del_rcu(), running on this same list. | |
355 | * However, it is perfectly legal to run concurrently with | |
356 | * the _rcu list-traversal primitives, such as | |
357 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
358 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
359 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
360 | */ | |
361 | static inline void hlist_add_head_rcu(struct hlist_node *n, | |
362 | struct hlist_head *h) | |
363 | { | |
364 | struct hlist_node *first = h->first; | |
10aa9d2c | 365 | |
82524746 FBH |
366 | n->next = first; |
367 | n->pprev = &h->first; | |
67bdbffd | 368 | rcu_assign_pointer(hlist_first_rcu(h), n); |
82524746 FBH |
369 | if (first) |
370 | first->pprev = &n->next; | |
82524746 FBH |
371 | } |
372 | ||
373 | /** | |
374 | * hlist_add_before_rcu | |
375 | * @n: the new element to add to the hash list. | |
376 | * @next: the existing element to add the new element before. | |
377 | * | |
378 | * Description: | |
379 | * Adds the specified element to the specified hlist | |
380 | * before the specified node while permitting racing traversals. | |
381 | * | |
382 | * The caller must take whatever precautions are necessary | |
383 | * (such as holding appropriate locks) to avoid racing | |
384 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
385 | * or hlist_del_rcu(), running on this same list. | |
386 | * However, it is perfectly legal to run concurrently with | |
387 | * the _rcu list-traversal primitives, such as | |
388 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
389 | * problems on Alpha CPUs. | |
390 | */ | |
391 | static inline void hlist_add_before_rcu(struct hlist_node *n, | |
392 | struct hlist_node *next) | |
393 | { | |
394 | n->pprev = next->pprev; | |
395 | n->next = next; | |
67bdbffd | 396 | rcu_assign_pointer(hlist_pprev_rcu(n), n); |
82524746 | 397 | next->pprev = &n->next; |
82524746 FBH |
398 | } |
399 | ||
400 | /** | |
401 | * hlist_add_after_rcu | |
402 | * @prev: the existing element to add the new element after. | |
403 | * @n: the new element to add to the hash list. | |
404 | * | |
405 | * Description: | |
406 | * Adds the specified element to the specified hlist | |
407 | * after the specified node while permitting racing traversals. | |
408 | * | |
409 | * The caller must take whatever precautions are necessary | |
410 | * (such as holding appropriate locks) to avoid racing | |
411 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
412 | * or hlist_del_rcu(), running on this same list. | |
413 | * However, it is perfectly legal to run concurrently with | |
414 | * the _rcu list-traversal primitives, such as | |
415 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
416 | * problems on Alpha CPUs. | |
417 | */ | |
418 | static inline void hlist_add_after_rcu(struct hlist_node *prev, | |
419 | struct hlist_node *n) | |
420 | { | |
421 | n->next = prev->next; | |
422 | n->pprev = &prev->next; | |
67bdbffd | 423 | rcu_assign_pointer(hlist_next_rcu(prev), n); |
82524746 FBH |
424 | if (n->next) |
425 | n->next->pprev = &n->next; | |
426 | } | |
427 | ||
67bdbffd AB |
428 | #define __hlist_for_each_rcu(pos, head) \ |
429 | for (pos = rcu_dereference(hlist_first_rcu(head)); \ | |
75d65a42 | 430 | pos; \ |
67bdbffd | 431 | pos = rcu_dereference(hlist_next_rcu(pos))) |
1cc52327 | 432 | |
82524746 FBH |
433 | /** |
434 | * hlist_for_each_entry_rcu - iterate over rcu list of given type | |
435 | * @tpos: the type * to use as a loop cursor. | |
436 | * @pos: the &struct hlist_node to use as a loop cursor. | |
437 | * @head: the head for your list. | |
438 | * @member: the name of the hlist_node within the struct. | |
439 | * | |
440 | * This list-traversal primitive may safely run concurrently with | |
441 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
442 | * as long as the traversal is guarded by rcu_read_lock(). | |
443 | */ | |
67bdbffd AB |
444 | #define hlist_for_each_entry_rcu(tpos, pos, head, member) \ |
445 | for (pos = rcu_dereference_raw(hlist_first_rcu(head)); \ | |
75d65a42 | 446 | pos && \ |
82524746 | 447 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
67bdbffd | 448 | pos = rcu_dereference_raw(hlist_next_rcu(pos))) |
82524746 | 449 | |
4f70ecca ED |
450 | /** |
451 | * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type | |
452 | * @tpos: the type * to use as a loop cursor. | |
453 | * @pos: the &struct hlist_node to use as a loop cursor. | |
454 | * @head: the head for your list. | |
455 | * @member: the name of the hlist_node within the struct. | |
456 | * | |
457 | * This list-traversal primitive may safely run concurrently with | |
458 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
459 | * as long as the traversal is guarded by rcu_read_lock(). | |
460 | */ | |
461 | #define hlist_for_each_entry_rcu_bh(tpos, pos, head, member) \ | |
462 | for (pos = rcu_dereference_bh((head)->first); \ | |
75d65a42 | 463 | pos && \ |
4f70ecca ED |
464 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
465 | pos = rcu_dereference_bh(pos->next)) | |
466 | ||
5c578aed | 467 | /** |
468 | * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point | |
469 | * @tpos: the type * to use as a loop cursor. | |
470 | * @pos: the &struct hlist_node to use as a loop cursor. | |
471 | * @member: the name of the hlist_node within the struct. | |
472 | */ | |
473 | #define hlist_for_each_entry_continue_rcu(tpos, pos, member) \ | |
474 | for (pos = rcu_dereference((pos)->next); \ | |
75d65a42 | 475 | pos && \ |
5c578aed | 476 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
477 | pos = rcu_dereference(pos->next)) | |
478 | ||
4f70ecca ED |
479 | /** |
480 | * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point | |
481 | * @tpos: the type * to use as a loop cursor. | |
482 | * @pos: the &struct hlist_node to use as a loop cursor. | |
483 | * @member: the name of the hlist_node within the struct. | |
484 | */ | |
485 | #define hlist_for_each_entry_continue_rcu_bh(tpos, pos, member) \ | |
486 | for (pos = rcu_dereference_bh((pos)->next); \ | |
75d65a42 | 487 | pos && \ |
4f70ecca ED |
488 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
489 | pos = rcu_dereference_bh(pos->next)) | |
490 | ||
5c578aed | 491 | |
82524746 FBH |
492 | #endif /* __KERNEL__ */ |
493 | #endif |