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Franck Bui-Huu82524742008-05-12 21:21:05 +02001#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>
Franck Bui-Huu10aa9d22008-05-12 21:21:06 +020010#include <linux/rcupdate.h>
Franck Bui-Huu82524742008-05-12 21:21:05 +020011
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 */
18static 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;
Franck Bui-Huu10aa9d22008-05-12 21:21:06 +020023 rcu_assign_pointer(prev->next, new);
Franck Bui-Huu82524742008-05-12 21:21:05 +020024 next->prev = new;
Franck Bui-Huu82524742008-05-12 21:21:05 +020025}
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 */
43static 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 */
64static 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 */
94static 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/**
Andrea Arcangeli6beeac72008-07-28 15:46:22 -0700101 * 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 */
120static 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/**
Franck Bui-Huu82524742008-05-12 21:21:05 +0200129 * 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 */
136static 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;
Franck Bui-Huu10aa9d22008-05-12 21:21:06 +0200141 rcu_assign_pointer(new->prev->next, new);
Franck Bui-Huu82524742008-05-12 21:21:05 +0200142 new->next->prev = new;
Franck Bui-Huu82524742008-05-12 21:21:05 +0200143 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 */
163static 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;
Franck Bui-Huu10aa9d22008-05-12 21:21:06 +0200196 rcu_assign_pointer(head->next, first);
Franck Bui-Huu82524742008-05-12 21:21:05 +0200197 first->prev = head;
198 at->prev = last;
199}
200
Jiri Pirko72c6a982009-04-14 17:33:57 +0200201/**
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
Franck Bui-Huu82524742008-05-12 21:21:05 +0200227#define __list_for_each_rcu(pos, head) \
Paul E. McKenney78b0e0e2008-05-12 21:21:06 +0200228 for (pos = rcu_dereference((head)->next); \
229 pos != (head); \
230 pos = rcu_dereference(pos->next))
Franck Bui-Huu82524742008-05-12 21:21:05 +0200231
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) \
Jiri Pirko72c6a982009-04-14 17:33:57 +0200243 for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \
Paul E. McKenney78b0e0e2008-05-12 21:21:06 +0200244 prefetch(pos->member.next), &pos->member != (head); \
Jiri Pirko72c6a982009-04-14 17:33:57 +0200245 pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
Franck Bui-Huu82524742008-05-12 21:21:05 +0200246
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) \
Paul E. McKenney78b0e0e2008-05-12 21:21:06 +0200260 for ((pos) = rcu_dereference((pos)->next); \
261 prefetch((pos)->next), (pos) != (head); \
262 (pos) = rcu_dereference((pos)->next))
Franck Bui-Huu82524742008-05-12 21:21:05 +0200263
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 */
283static 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 */
296static 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;
Franck Bui-Huu10aa9d22008-05-12 21:21:06 +0200303 rcu_assign_pointer(*new->pprev, new);
Franck Bui-Huu82524742008-05-12 21:21:05 +0200304 if (next)
305 new->next->pprev = &new->next;
Franck Bui-Huu82524742008-05-12 21:21:05 +0200306 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 */
328static inline void hlist_add_head_rcu(struct hlist_node *n,
329 struct hlist_head *h)
330{
331 struct hlist_node *first = h->first;
Franck Bui-Huu10aa9d22008-05-12 21:21:06 +0200332
Franck Bui-Huu82524742008-05-12 21:21:05 +0200333 n->next = first;
334 n->pprev = &h->first;
Franck Bui-Huu10aa9d22008-05-12 21:21:06 +0200335 rcu_assign_pointer(h->first, n);
Franck Bui-Huu82524742008-05-12 21:21:05 +0200336 if (first)
337 first->pprev = &n->next;
Franck Bui-Huu82524742008-05-12 21:21:05 +0200338}
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 */
358static 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;
Franck Bui-Huu10aa9d22008-05-12 21:21:06 +0200363 rcu_assign_pointer(*(n->pprev), n);
Franck Bui-Huu82524742008-05-12 21:21:05 +0200364 next->pprev = &n->next;
Franck Bui-Huu82524742008-05-12 21:21:05 +0200365}
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 */
385static 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;
Franck Bui-Huu10aa9d22008-05-12 21:21:06 +0200390 rcu_assign_pointer(prev->next, n);
Franck Bui-Huu82524742008-05-12 21:21:05 +0200391 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) \
Paul E. McKenney78b0e0e2008-05-12 21:21:06 +0200407 for (pos = rcu_dereference((head)->first); \
408 pos && ({ prefetch(pos->next); 1; }) && \
Franck Bui-Huu82524742008-05-12 21:21:05 +0200409 ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
Paul E. McKenney78b0e0e2008-05-12 21:21:06 +0200410 pos = rcu_dereference(pos->next))
Franck Bui-Huu82524742008-05-12 21:21:05 +0200411
412#endif /* __KERNEL__ */
413#endif