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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 | * Insert a new entry between two known consecutive entries. |
14 | * |
15 | * This is only for internal list manipulation where we know |
16 | * the prev/next entries already! |
17 | */ |
18 | static inline void __list_add_rcu(struct list_head *new, |
19 | struct list_head *prev, struct list_head *next) |
20 | { |
21 | new->next = next; |
22 | new->prev = prev; |
23 | rcu_assign_pointer(prev->next, new); |
24 | next->prev = new; |
25 | } |
26 | |
27 | /** |
28 | * list_add_rcu - add a new entry to rcu-protected list |
29 | * @new: new entry to be added |
30 | * @head: list head to add it after |
31 | * |
32 | * Insert a new entry after the specified head. |
33 | * This is good for implementing stacks. |
34 | * |
35 | * The caller must take whatever precautions are necessary |
36 | * (such as holding appropriate locks) to avoid racing |
37 | * with another list-mutation primitive, such as list_add_rcu() |
38 | * or list_del_rcu(), running on this same list. |
39 | * However, it is perfectly legal to run concurrently with |
40 | * the _rcu list-traversal primitives, such as |
41 | * list_for_each_entry_rcu(). |
42 | */ |
43 | static inline void list_add_rcu(struct list_head *new, struct list_head *head) |
44 | { |
45 | __list_add_rcu(new, head, head->next); |
46 | } |
47 | |
48 | /** |
49 | * list_add_tail_rcu - add a new entry to rcu-protected list |
50 | * @new: new entry to be added |
51 | * @head: list head to add it before |
52 | * |
53 | * Insert a new entry before the specified head. |
54 | * This is useful for implementing queues. |
55 | * |
56 | * The caller must take whatever precautions are necessary |
57 | * (such as holding appropriate locks) to avoid racing |
58 | * with another list-mutation primitive, such as list_add_tail_rcu() |
59 | * or list_del_rcu(), running on this same list. |
60 | * However, it is perfectly legal to run concurrently with |
61 | * the _rcu list-traversal primitives, such as |
62 | * list_for_each_entry_rcu(). |
63 | */ |
64 | static inline void list_add_tail_rcu(struct list_head *new, |
65 | struct list_head *head) |
66 | { |
67 | __list_add_rcu(new, head->prev, head); |
68 | } |
69 | |
70 | /** |
71 | * list_del_rcu - deletes entry from list without re-initialization |
72 | * @entry: the element to delete from the list. |
73 | * |
74 | * Note: list_empty() on entry does not return true after this, |
75 | * the entry is in an undefined state. It is useful for RCU based |
76 | * lockfree traversal. |
77 | * |
78 | * In particular, it means that we can not poison the forward |
79 | * pointers that may still be used for walking the list. |
80 | * |
81 | * The caller must take whatever precautions are necessary |
82 | * (such as holding appropriate locks) to avoid racing |
83 | * with another list-mutation primitive, such as list_del_rcu() |
84 | * or list_add_rcu(), running on this same list. |
85 | * However, it is perfectly legal to run concurrently with |
86 | * the _rcu list-traversal primitives, such as |
87 | * list_for_each_entry_rcu(). |
88 | * |
89 | * Note that the caller is not permitted to immediately free |
90 | * the newly deleted entry. Instead, either synchronize_rcu() |
91 | * or call_rcu() must be used to defer freeing until an RCU |
92 | * grace period has elapsed. |
93 | */ |
94 | static inline void list_del_rcu(struct list_head *entry) |
95 | { |
96 | __list_del(entry->prev, entry->next); |
97 | entry->prev = LIST_POISON2; |
98 | } |
99 | |
100 | /** |
101 | * hlist_del_init_rcu - deletes entry from hash list with re-initialization |
102 | * @n: the element to delete from the hash list. |
103 | * |
104 | * Note: list_unhashed() on the node return true after this. It is |
105 | * useful for RCU based read lockfree traversal if the writer side |
106 | * must know if the list entry is still hashed or already unhashed. |
107 | * |
108 | * In particular, it means that we can not poison the forward pointers |
109 | * that may still be used for walking the hash list and we can only |
110 | * zero the pprev pointer so list_unhashed() will return true after |
111 | * this. |
112 | * |
113 | * The caller must take whatever precautions are necessary (such as |
114 | * holding appropriate locks) to avoid racing with another |
115 | * list-mutation primitive, such as hlist_add_head_rcu() or |
116 | * hlist_del_rcu(), running on this same list. However, it is |
117 | * perfectly legal to run concurrently with the _rcu list-traversal |
118 | * primitives, such as hlist_for_each_entry_rcu(). |
119 | */ |
120 | static inline void hlist_del_init_rcu(struct hlist_node *n) |
121 | { |
122 | if (!hlist_unhashed(n)) { |
123 | __hlist_del(n); |
124 | n->pprev = NULL; |
125 | } |
126 | } |
127 | |
128 | /** |
129 | * list_replace_rcu - replace old entry by new one |
130 | * @old : the element to be replaced |
131 | * @new : the new element to insert |
132 | * |
133 | * The @old entry will be replaced with the @new entry atomically. |
134 | * Note: @old should not be empty. |
135 | */ |
136 | static inline void list_replace_rcu(struct list_head *old, |
137 | struct list_head *new) |
138 | { |
139 | new->next = old->next; |
140 | new->prev = old->prev; |
141 | rcu_assign_pointer(new->prev->next, new); |
142 | new->next->prev = new; |
143 | old->prev = LIST_POISON2; |
144 | } |
145 | |
146 | /** |
147 | * list_splice_init_rcu - splice an RCU-protected list into an existing list. |
148 | * @list: the RCU-protected list to splice |
149 | * @head: the place in the list to splice the first list into |
150 | * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ... |
151 | * |
152 | * @head can be RCU-read traversed concurrently with this function. |
153 | * |
154 | * Note that this function blocks. |
155 | * |
156 | * Important note: the caller must take whatever action is necessary to |
157 | * prevent any other updates to @head. In principle, it is possible |
158 | * to modify the list as soon as sync() begins execution. |
159 | * If this sort of thing becomes necessary, an alternative version |
160 | * based on call_rcu() could be created. But only if -really- |
161 | * needed -- there is no shortage of RCU API members. |
162 | */ |
163 | static inline void list_splice_init_rcu(struct list_head *list, |
164 | struct list_head *head, |
165 | void (*sync)(void)) |
166 | { |
167 | struct list_head *first = list->next; |
168 | struct list_head *last = list->prev; |
169 | struct list_head *at = head->next; |
170 | |
171 | if (list_empty(head)) |
172 | return; |
173 | |
174 | /* "first" and "last" tracking list, so initialize it. */ |
175 | |
176 | INIT_LIST_HEAD(list); |
177 | |
178 | /* |
179 | * At this point, the list body still points to the source list. |
180 | * Wait for any readers to finish using the list before splicing |
181 | * the list body into the new list. Any new readers will see |
182 | * an empty list. |
183 | */ |
184 | |
185 | sync(); |
186 | |
187 | /* |
188 | * Readers are finished with the source list, so perform splice. |
189 | * The order is important if the new list is global and accessible |
190 | * to concurrent RCU readers. Note that RCU readers are not |
191 | * permitted to traverse the prev pointers without excluding |
192 | * this function. |
193 | */ |
194 | |
195 | last->next = at; |
196 | rcu_assign_pointer(head->next, first); |
197 | first->prev = head; |
198 | at->prev = last; |
199 | } |
200 | |
201 | /** |
202 | * list_entry_rcu - get the struct for this entry |
203 | * @ptr: the &struct list_head pointer. |
204 | * @type: the type of the struct this is embedded in. |
205 | * @member: the name of the list_struct within the struct. |
206 | * |
207 | * This primitive may safely run concurrently with the _rcu list-mutation |
208 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). |
209 | */ |
210 | #define list_entry_rcu(ptr, type, member) \ |
211 | container_of(rcu_dereference(ptr), type, member) |
212 | |
213 | /** |
214 | * list_first_entry_rcu - get the first element from a list |
215 | * @ptr: the list head to take the element from. |
216 | * @type: the type of the struct this is embedded in. |
217 | * @member: the name of the list_struct within the struct. |
218 | * |
219 | * Note, that list is expected to be not empty. |
220 | * |
221 | * This primitive may safely run concurrently with the _rcu list-mutation |
222 | * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock(). |
223 | */ |
224 | #define list_first_entry_rcu(ptr, type, member) \ |
225 | list_entry_rcu((ptr)->next, type, member) |
226 | |
227 | #define __list_for_each_rcu(pos, head) \ |
228 | for (pos = rcu_dereference((head)->next); \ |
229 | pos != (head); \ |
230 | pos = rcu_dereference(pos->next)) |
231 | |
232 | /** |
233 | * list_for_each_entry_rcu - iterate over rcu list of given type |
234 | * @pos: the type * to use as a loop cursor. |
235 | * @head: the head for your list. |
236 | * @member: the name of the list_struct within the struct. |
237 | * |
238 | * This list-traversal primitive may safely run concurrently with |
239 | * the _rcu list-mutation primitives such as list_add_rcu() |
240 | * as long as the traversal is guarded by rcu_read_lock(). |
241 | */ |
242 | #define list_for_each_entry_rcu(pos, head, member) \ |
243 | for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \ |
244 | prefetch(pos->member.next), &pos->member != (head); \ |
245 | pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) |
246 | |
247 | |
248 | /** |
249 | * list_for_each_continue_rcu |
250 | * @pos: the &struct list_head to use as a loop cursor. |
251 | * @head: the head for your list. |
252 | * |
253 | * Iterate over an rcu-protected list, continuing after current point. |
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_continue_rcu(pos, head) \ |
260 | for ((pos) = rcu_dereference((pos)->next); \ |
261 | prefetch((pos)->next), (pos) != (head); \ |
262 | (pos) = rcu_dereference((pos)->next)) |
263 | |
264 | /** |
265 | * hlist_del_rcu - deletes entry from hash list without re-initialization |
266 | * @n: the element to delete from the hash list. |
267 | * |
268 | * Note: list_unhashed() on entry does not return true after this, |
269 | * the entry is in an undefined state. It is useful for RCU based |
270 | * lockfree traversal. |
271 | * |
272 | * In particular, it means that we can not poison the forward |
273 | * pointers that may still be used for walking the hash list. |
274 | * |
275 | * The caller must take whatever precautions are necessary |
276 | * (such as holding appropriate locks) to avoid racing |
277 | * with another list-mutation primitive, such as hlist_add_head_rcu() |
278 | * or hlist_del_rcu(), running on this same list. |
279 | * However, it is perfectly legal to run concurrently with |
280 | * the _rcu list-traversal primitives, such as |
281 | * hlist_for_each_entry(). |
282 | */ |
283 | static inline void hlist_del_rcu(struct hlist_node *n) |
284 | { |
285 | __hlist_del(n); |
286 | n->pprev = LIST_POISON2; |
287 | } |
288 | |
289 | /** |
290 | * hlist_replace_rcu - replace old entry by new one |
291 | * @old : the element to be replaced |
292 | * @new : the new element to insert |
293 | * |
294 | * The @old entry will be replaced with the @new entry atomically. |
295 | */ |
296 | static inline void hlist_replace_rcu(struct hlist_node *old, |
297 | struct hlist_node *new) |
298 | { |
299 | struct hlist_node *next = old->next; |
300 | |
301 | new->next = next; |
302 | new->pprev = old->pprev; |
303 | rcu_assign_pointer(*new->pprev, new); |
304 | if (next) |
305 | new->next->pprev = &new->next; |
306 | old->pprev = LIST_POISON2; |
307 | } |
308 | |
309 | /** |
310 | * hlist_add_head_rcu |
311 | * @n: the element to add to the hash list. |
312 | * @h: the list to add to. |
313 | * |
314 | * Description: |
315 | * Adds the specified element to the specified hlist, |
316 | * while permitting racing traversals. |
317 | * |
318 | * The caller must take whatever precautions are necessary |
319 | * (such as holding appropriate locks) to avoid racing |
320 | * with another list-mutation primitive, such as hlist_add_head_rcu() |
321 | * or hlist_del_rcu(), running on this same list. |
322 | * However, it is perfectly legal to run concurrently with |
323 | * the _rcu list-traversal primitives, such as |
324 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency |
325 | * problems on Alpha CPUs. Regardless of the type of CPU, the |
326 | * list-traversal primitive must be guarded by rcu_read_lock(). |
327 | */ |
328 | static inline void hlist_add_head_rcu(struct hlist_node *n, |
329 | struct hlist_head *h) |
330 | { |
331 | struct hlist_node *first = h->first; |
332 | |
333 | n->next = first; |
334 | n->pprev = &h->first; |
335 | rcu_assign_pointer(h->first, n); |
336 | if (first) |
337 | first->pprev = &n->next; |
338 | } |
339 | |
340 | /** |
341 | * hlist_add_before_rcu |
342 | * @n: the new element to add to the hash list. |
343 | * @next: the existing element to add the new element before. |
344 | * |
345 | * Description: |
346 | * Adds the specified element to the specified hlist |
347 | * before the specified node while permitting racing traversals. |
348 | * |
349 | * The caller must take whatever precautions are necessary |
350 | * (such as holding appropriate locks) to avoid racing |
351 | * with another list-mutation primitive, such as hlist_add_head_rcu() |
352 | * or hlist_del_rcu(), running on this same list. |
353 | * However, it is perfectly legal to run concurrently with |
354 | * the _rcu list-traversal primitives, such as |
355 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency |
356 | * problems on Alpha CPUs. |
357 | */ |
358 | static inline void hlist_add_before_rcu(struct hlist_node *n, |
359 | struct hlist_node *next) |
360 | { |
361 | n->pprev = next->pprev; |
362 | n->next = next; |
363 | rcu_assign_pointer(*(n->pprev), n); |
364 | next->pprev = &n->next; |
365 | } |
366 | |
367 | /** |
368 | * hlist_add_after_rcu |
369 | * @prev: the existing element to add the new element after. |
370 | * @n: the new element to add to the hash list. |
371 | * |
372 | * Description: |
373 | * Adds the specified element to the specified hlist |
374 | * after the specified node while permitting racing traversals. |
375 | * |
376 | * The caller must take whatever precautions are necessary |
377 | * (such as holding appropriate locks) to avoid racing |
378 | * with another list-mutation primitive, such as hlist_add_head_rcu() |
379 | * or hlist_del_rcu(), running on this same list. |
380 | * However, it is perfectly legal to run concurrently with |
381 | * the _rcu list-traversal primitives, such as |
382 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency |
383 | * problems on Alpha CPUs. |
384 | */ |
385 | static inline void hlist_add_after_rcu(struct hlist_node *prev, |
386 | struct hlist_node *n) |
387 | { |
388 | n->next = prev->next; |
389 | n->pprev = &prev->next; |
390 | rcu_assign_pointer(prev->next, n); |
391 | if (n->next) |
392 | n->next->pprev = &n->next; |
393 | } |
394 | |
395 | /** |
396 | * hlist_for_each_entry_rcu - iterate over rcu list of given type |
397 | * @tpos: the type * to use as a loop cursor. |
398 | * @pos: the &struct hlist_node to use as a loop cursor. |
399 | * @head: the head for your list. |
400 | * @member: the name of the hlist_node within the struct. |
401 | * |
402 | * This list-traversal primitive may safely run concurrently with |
403 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() |
404 | * as long as the traversal is guarded by rcu_read_lock(). |
405 | */ |
406 | #define hlist_for_each_entry_rcu(tpos, pos, head, member) \ |
407 | for (pos = rcu_dereference((head)->first); \ |
408 | pos && ({ prefetch(pos->next); 1; }) && \ |
409 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
410 | pos = rcu_dereference(pos->next)) |
411 | |
412 | #endif /* __KERNEL__ */ |
413 | #endif |
414 |
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