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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 FBH |
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; | |
10aa9d2c | 23 | rcu_assign_pointer(prev->next, new); |
82524746 | 24 | next->prev = new; |
82524746 FBH |
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 | ||
6beeac76 AA |
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 | ||
82524746 FBH |
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; | |
10aa9d2c | 141 | rcu_assign_pointer(new->prev->next, new); |
82524746 | 142 | new->next->prev = new; |
82524746 FBH |
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; | |
10aa9d2c | 196 | rcu_assign_pointer(head->next, first); |
82524746 FBH |
197 | first->prev = head; |
198 | at->prev = last; | |
199 | } | |
200 | ||
82524746 | 201 | #define __list_for_each_rcu(pos, head) \ |
78b0e0e9 PM |
202 | for (pos = rcu_dereference((head)->next); \ |
203 | pos != (head); \ | |
204 | pos = rcu_dereference(pos->next)) | |
82524746 FBH |
205 | |
206 | /** | |
207 | * list_for_each_entry_rcu - iterate over rcu list of given type | |
208 | * @pos: the type * to use as a loop cursor. | |
209 | * @head: the head for your list. | |
210 | * @member: the name of the list_struct within the struct. | |
211 | * | |
212 | * This list-traversal primitive may safely run concurrently with | |
213 | * the _rcu list-mutation primitives such as list_add_rcu() | |
214 | * as long as the traversal is guarded by rcu_read_lock(). | |
215 | */ | |
216 | #define list_for_each_entry_rcu(pos, head, member) \ | |
78b0e0e9 PM |
217 | for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \ |
218 | prefetch(pos->member.next), &pos->member != (head); \ | |
219 | pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member)) | |
82524746 FBH |
220 | |
221 | ||
222 | /** | |
223 | * list_for_each_continue_rcu | |
224 | * @pos: the &struct list_head to use as a loop cursor. | |
225 | * @head: the head for your list. | |
226 | * | |
227 | * Iterate over an rcu-protected list, continuing after current point. | |
228 | * | |
229 | * This list-traversal primitive may safely run concurrently with | |
230 | * the _rcu list-mutation primitives such as list_add_rcu() | |
231 | * as long as the traversal is guarded by rcu_read_lock(). | |
232 | */ | |
233 | #define list_for_each_continue_rcu(pos, head) \ | |
78b0e0e9 PM |
234 | for ((pos) = rcu_dereference((pos)->next); \ |
235 | prefetch((pos)->next), (pos) != (head); \ | |
236 | (pos) = rcu_dereference((pos)->next)) | |
82524746 FBH |
237 | |
238 | /** | |
239 | * hlist_del_rcu - deletes entry from hash list without re-initialization | |
240 | * @n: the element to delete from the hash list. | |
241 | * | |
242 | * Note: list_unhashed() on entry does not return true after this, | |
243 | * the entry is in an undefined state. It is useful for RCU based | |
244 | * lockfree traversal. | |
245 | * | |
246 | * In particular, it means that we can not poison the forward | |
247 | * pointers that may still be used for walking the hash list. | |
248 | * | |
249 | * The caller must take whatever precautions are necessary | |
250 | * (such as holding appropriate locks) to avoid racing | |
251 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
252 | * or hlist_del_rcu(), running on this same list. | |
253 | * However, it is perfectly legal to run concurrently with | |
254 | * the _rcu list-traversal primitives, such as | |
255 | * hlist_for_each_entry(). | |
256 | */ | |
257 | static inline void hlist_del_rcu(struct hlist_node *n) | |
258 | { | |
259 | __hlist_del(n); | |
260 | n->pprev = LIST_POISON2; | |
261 | } | |
262 | ||
263 | /** | |
264 | * hlist_replace_rcu - replace old entry by new one | |
265 | * @old : the element to be replaced | |
266 | * @new : the new element to insert | |
267 | * | |
268 | * The @old entry will be replaced with the @new entry atomically. | |
269 | */ | |
270 | static inline void hlist_replace_rcu(struct hlist_node *old, | |
271 | struct hlist_node *new) | |
272 | { | |
273 | struct hlist_node *next = old->next; | |
274 | ||
275 | new->next = next; | |
276 | new->pprev = old->pprev; | |
10aa9d2c | 277 | rcu_assign_pointer(*new->pprev, new); |
82524746 FBH |
278 | if (next) |
279 | new->next->pprev = &new->next; | |
82524746 FBH |
280 | old->pprev = LIST_POISON2; |
281 | } | |
282 | ||
283 | /** | |
284 | * hlist_add_head_rcu | |
285 | * @n: the element to add to the hash list. | |
286 | * @h: the list to add to. | |
287 | * | |
288 | * Description: | |
289 | * Adds the specified element to the specified hlist, | |
290 | * while permitting racing traversals. | |
291 | * | |
292 | * The caller must take whatever precautions are necessary | |
293 | * (such as holding appropriate locks) to avoid racing | |
294 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
295 | * or hlist_del_rcu(), running on this same list. | |
296 | * However, it is perfectly legal to run concurrently with | |
297 | * the _rcu list-traversal primitives, such as | |
298 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
299 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
300 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
301 | */ | |
302 | static inline void hlist_add_head_rcu(struct hlist_node *n, | |
303 | struct hlist_head *h) | |
304 | { | |
305 | struct hlist_node *first = h->first; | |
10aa9d2c | 306 | |
82524746 FBH |
307 | n->next = first; |
308 | n->pprev = &h->first; | |
10aa9d2c | 309 | rcu_assign_pointer(h->first, n); |
82524746 FBH |
310 | if (first) |
311 | first->pprev = &n->next; | |
82524746 FBH |
312 | } |
313 | ||
314 | /** | |
315 | * hlist_add_before_rcu | |
316 | * @n: the new element to add to the hash list. | |
317 | * @next: the existing element to add the new element before. | |
318 | * | |
319 | * Description: | |
320 | * Adds the specified element to the specified hlist | |
321 | * before the specified node while permitting racing traversals. | |
322 | * | |
323 | * The caller must take whatever precautions are necessary | |
324 | * (such as holding appropriate locks) to avoid racing | |
325 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
326 | * or hlist_del_rcu(), running on this same list. | |
327 | * However, it is perfectly legal to run concurrently with | |
328 | * the _rcu list-traversal primitives, such as | |
329 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
330 | * problems on Alpha CPUs. | |
331 | */ | |
332 | static inline void hlist_add_before_rcu(struct hlist_node *n, | |
333 | struct hlist_node *next) | |
334 | { | |
335 | n->pprev = next->pprev; | |
336 | n->next = next; | |
10aa9d2c | 337 | rcu_assign_pointer(*(n->pprev), n); |
82524746 | 338 | next->pprev = &n->next; |
82524746 FBH |
339 | } |
340 | ||
341 | /** | |
342 | * hlist_add_after_rcu | |
343 | * @prev: the existing element to add the new element after. | |
344 | * @n: the new element to add to the hash list. | |
345 | * | |
346 | * Description: | |
347 | * Adds the specified element to the specified hlist | |
348 | * after the specified node while permitting racing traversals. | |
349 | * | |
350 | * The caller must take whatever precautions are necessary | |
351 | * (such as holding appropriate locks) to avoid racing | |
352 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
353 | * or hlist_del_rcu(), running on this same list. | |
354 | * However, it is perfectly legal to run concurrently with | |
355 | * the _rcu list-traversal primitives, such as | |
356 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
357 | * problems on Alpha CPUs. | |
358 | */ | |
359 | static inline void hlist_add_after_rcu(struct hlist_node *prev, | |
360 | struct hlist_node *n) | |
361 | { | |
362 | n->next = prev->next; | |
363 | n->pprev = &prev->next; | |
10aa9d2c | 364 | rcu_assign_pointer(prev->next, n); |
82524746 FBH |
365 | if (n->next) |
366 | n->next->pprev = &n->next; | |
367 | } | |
368 | ||
369 | /** | |
370 | * hlist_for_each_entry_rcu - iterate over rcu list of given type | |
371 | * @tpos: the type * to use as a loop cursor. | |
372 | * @pos: the &struct hlist_node to use as a loop cursor. | |
373 | * @head: the head for your list. | |
374 | * @member: the name of the hlist_node within the struct. | |
375 | * | |
376 | * This list-traversal primitive may safely run concurrently with | |
377 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
378 | * as long as the traversal is guarded by rcu_read_lock(). | |
379 | */ | |
380 | #define hlist_for_each_entry_rcu(tpos, pos, head, member) \ | |
78b0e0e9 PM |
381 | for (pos = rcu_dereference((head)->first); \ |
382 | pos && ({ prefetch(pos->next); 1; }) && \ | |
82524746 | 383 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ |
78b0e0e9 | 384 | pos = rcu_dereference(pos->next)) |
82524746 FBH |
385 | |
386 | #endif /* __KERNEL__ */ | |
387 | #endif |