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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> |
10 | #include <linux/rcupdate.h> |
11 | |
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 | |
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 | |
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; |
38 | rcu_assign_pointer(list_next_rcu(prev), new); |
39 | next->prev = new; |
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 | |
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 | |
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; |
156 | rcu_assign_pointer(list_next_rcu(new->prev), new); |
157 | new->next->prev = new; |
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; |
211 | rcu_assign_pointer(list_next_rcu(head), first); |
212 | first->prev = head; |
213 | at->prev = last; |
214 | } |
215 | |
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) \ |
226 | ({typeof (*ptr) __rcu *__ptr = (typeof (*ptr) __rcu __force *)ptr; \ |
227 | container_of((typeof(ptr))rcu_dereference_raw(__ptr), type, member); \ |
228 | }) |
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 | |
244 | #define __list_for_each_rcu(pos, head) \ |
245 | for (pos = rcu_dereference_raw(list_next_rcu(head)); \ |
246 | pos != (head); \ |
247 | pos = rcu_dereference_raw(list_next_rcu((pos))) |
248 | |
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) \ |
260 | for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \ |
261 | prefetch(pos->member.next), &pos->member != (head); \ |
262 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
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) \ |
277 | for ((pos) = rcu_dereference_raw(list_next_rcu(pos)); \ |
278 | prefetch((pos)->next), (pos) != (head); \ |
279 | (pos) = rcu_dereference_raw(list_next_rcu(pos))) |
280 | |
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); \ |
292 | prefetch(pos->member.next), &pos->member != (head); \ |
293 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
294 | |
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; |
334 | rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new); |
335 | if (next) |
336 | new->next->pprev = &new->next; |
337 | old->pprev = LIST_POISON2; |
338 | } |
339 | |
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 | |
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; |
370 | |
371 | n->next = first; |
372 | n->pprev = &h->first; |
373 | rcu_assign_pointer(hlist_first_rcu(h), n); |
374 | if (first) |
375 | first->pprev = &n->next; |
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; |
401 | rcu_assign_pointer(hlist_pprev_rcu(n), n); |
402 | next->pprev = &n->next; |
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; |
428 | rcu_assign_pointer(hlist_next_rcu(prev), n); |
429 | if (n->next) |
430 | n->next->pprev = &n->next; |
431 | } |
432 | |
433 | #define __hlist_for_each_rcu(pos, head) \ |
434 | for (pos = rcu_dereference(hlist_first_rcu(head)); \ |
435 | pos && ({ prefetch(pos->next); 1; }); \ |
436 | pos = rcu_dereference(hlist_next_rcu(pos))) |
437 | |
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 | */ |
449 | #define hlist_for_each_entry_rcu(tpos, pos, head, member) \ |
450 | for (pos = rcu_dereference_raw(hlist_first_rcu(head)); \ |
451 | pos && ({ prefetch(pos->next); 1; }) && \ |
452 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
453 | pos = rcu_dereference_raw(hlist_next_rcu(pos))) |
454 | |
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); \ |
468 | pos && ({ prefetch(pos->next); 1; }) && \ |
469 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
470 | pos = rcu_dereference_bh(pos->next)) |
471 | |
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); \ |
480 | pos && ({ prefetch(pos->next); 1; }) && \ |
481 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
482 | pos = rcu_dereference(pos->next)) |
483 | |
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); \ |
492 | pos && ({ prefetch(pos->next); 1; }) && \ |
493 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
494 | pos = rcu_dereference_bh(pos->next)) |
495 | |
496 | |
497 | #endif /* __KERNEL__ */ |
498 | #endif |
499 |
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