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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> | |
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 | ||
100 | /** | |
101 | * list_replace_rcu - replace old entry by new one | |
102 | * @old : the element to be replaced | |
103 | * @new : the new element to insert | |
104 | * | |
105 | * The @old entry will be replaced with the @new entry atomically. | |
106 | * Note: @old should not be empty. | |
107 | */ | |
108 | static inline void list_replace_rcu(struct list_head *old, | |
109 | struct list_head *new) | |
110 | { | |
111 | new->next = old->next; | |
112 | new->prev = old->prev; | |
10aa9d2c | 113 | rcu_assign_pointer(new->prev->next, new); |
82524746 | 114 | new->next->prev = new; |
82524746 FBH |
115 | old->prev = LIST_POISON2; |
116 | } | |
117 | ||
118 | /** | |
119 | * list_splice_init_rcu - splice an RCU-protected list into an existing list. | |
120 | * @list: the RCU-protected list to splice | |
121 | * @head: the place in the list to splice the first list into | |
122 | * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ... | |
123 | * | |
124 | * @head can be RCU-read traversed concurrently with this function. | |
125 | * | |
126 | * Note that this function blocks. | |
127 | * | |
128 | * Important note: the caller must take whatever action is necessary to | |
129 | * prevent any other updates to @head. In principle, it is possible | |
130 | * to modify the list as soon as sync() begins execution. | |
131 | * If this sort of thing becomes necessary, an alternative version | |
132 | * based on call_rcu() could be created. But only if -really- | |
133 | * needed -- there is no shortage of RCU API members. | |
134 | */ | |
135 | static inline void list_splice_init_rcu(struct list_head *list, | |
136 | struct list_head *head, | |
137 | void (*sync)(void)) | |
138 | { | |
139 | struct list_head *first = list->next; | |
140 | struct list_head *last = list->prev; | |
141 | struct list_head *at = head->next; | |
142 | ||
143 | if (list_empty(head)) | |
144 | return; | |
145 | ||
146 | /* "first" and "last" tracking list, so initialize it. */ | |
147 | ||
148 | INIT_LIST_HEAD(list); | |
149 | ||
150 | /* | |
151 | * At this point, the list body still points to the source list. | |
152 | * Wait for any readers to finish using the list before splicing | |
153 | * the list body into the new list. Any new readers will see | |
154 | * an empty list. | |
155 | */ | |
156 | ||
157 | sync(); | |
158 | ||
159 | /* | |
160 | * Readers are finished with the source list, so perform splice. | |
161 | * The order is important if the new list is global and accessible | |
162 | * to concurrent RCU readers. Note that RCU readers are not | |
163 | * permitted to traverse the prev pointers without excluding | |
164 | * this function. | |
165 | */ | |
166 | ||
167 | last->next = at; | |
10aa9d2c | 168 | rcu_assign_pointer(head->next, first); |
82524746 FBH |
169 | first->prev = head; |
170 | at->prev = last; | |
171 | } | |
172 | ||
173 | /** | |
174 | * list_for_each_rcu - iterate over an rcu-protected list | |
175 | * @pos: the &struct list_head to use as a loop cursor. | |
176 | * @head: the head for your list. | |
177 | * | |
178 | * This list-traversal primitive may safely run concurrently with | |
179 | * the _rcu list-mutation primitives such as list_add_rcu() | |
180 | * as long as the traversal is guarded by rcu_read_lock(). | |
181 | */ | |
182 | #define list_for_each_rcu(pos, head) \ | |
183 | for (pos = (head)->next; \ | |
184 | prefetch(rcu_dereference(pos)->next), pos != (head); \ | |
185 | pos = pos->next) | |
186 | ||
187 | #define __list_for_each_rcu(pos, head) \ | |
188 | for (pos = (head)->next; \ | |
189 | rcu_dereference(pos) != (head); \ | |
190 | pos = pos->next) | |
191 | ||
192 | /** | |
193 | * list_for_each_safe_rcu | |
194 | * @pos: the &struct list_head to use as a loop cursor. | |
195 | * @n: another &struct list_head to use as temporary storage | |
196 | * @head: the head for your list. | |
197 | * | |
198 | * Iterate over an rcu-protected list, safe against removal of list entry. | |
199 | * | |
200 | * This list-traversal primitive may safely run concurrently with | |
201 | * the _rcu list-mutation primitives such as list_add_rcu() | |
202 | * as long as the traversal is guarded by rcu_read_lock(). | |
203 | */ | |
204 | #define list_for_each_safe_rcu(pos, n, head) \ | |
205 | for (pos = (head)->next; \ | |
206 | n = rcu_dereference(pos)->next, pos != (head); \ | |
207 | pos = n) | |
208 | ||
209 | /** | |
210 | * list_for_each_entry_rcu - iterate over rcu list of given type | |
211 | * @pos: the type * to use as a loop cursor. | |
212 | * @head: the head for your list. | |
213 | * @member: the name of the list_struct within the struct. | |
214 | * | |
215 | * This list-traversal primitive may safely run concurrently with | |
216 | * the _rcu list-mutation primitives such as list_add_rcu() | |
217 | * as long as the traversal is guarded by rcu_read_lock(). | |
218 | */ | |
219 | #define list_for_each_entry_rcu(pos, head, member) \ | |
220 | for (pos = list_entry((head)->next, typeof(*pos), member); \ | |
221 | prefetch(rcu_dereference(pos)->member.next), \ | |
222 | &pos->member != (head); \ | |
223 | pos = list_entry(pos->member.next, typeof(*pos), member)) | |
224 | ||
225 | ||
226 | /** | |
227 | * list_for_each_continue_rcu | |
228 | * @pos: the &struct list_head to use as a loop cursor. | |
229 | * @head: the head for your list. | |
230 | * | |
231 | * Iterate over an rcu-protected list, continuing after current point. | |
232 | * | |
233 | * This list-traversal primitive may safely run concurrently with | |
234 | * the _rcu list-mutation primitives such as list_add_rcu() | |
235 | * as long as the traversal is guarded by rcu_read_lock(). | |
236 | */ | |
237 | #define list_for_each_continue_rcu(pos, head) \ | |
238 | for ((pos) = (pos)->next; \ | |
239 | prefetch(rcu_dereference((pos))->next), (pos) != (head); \ | |
240 | (pos) = (pos)->next) | |
241 | ||
242 | /** | |
243 | * hlist_del_rcu - deletes entry from hash list without re-initialization | |
244 | * @n: the element to delete from the hash list. | |
245 | * | |
246 | * Note: list_unhashed() on entry does not return true after this, | |
247 | * the entry is in an undefined state. It is useful for RCU based | |
248 | * lockfree traversal. | |
249 | * | |
250 | * In particular, it means that we can not poison the forward | |
251 | * pointers that may still be used for walking the hash list. | |
252 | * | |
253 | * The caller must take whatever precautions are necessary | |
254 | * (such as holding appropriate locks) to avoid racing | |
255 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
256 | * or hlist_del_rcu(), running on this same list. | |
257 | * However, it is perfectly legal to run concurrently with | |
258 | * the _rcu list-traversal primitives, such as | |
259 | * hlist_for_each_entry(). | |
260 | */ | |
261 | static inline void hlist_del_rcu(struct hlist_node *n) | |
262 | { | |
263 | __hlist_del(n); | |
264 | n->pprev = LIST_POISON2; | |
265 | } | |
266 | ||
267 | /** | |
268 | * hlist_replace_rcu - replace old entry by new one | |
269 | * @old : the element to be replaced | |
270 | * @new : the new element to insert | |
271 | * | |
272 | * The @old entry will be replaced with the @new entry atomically. | |
273 | */ | |
274 | static inline void hlist_replace_rcu(struct hlist_node *old, | |
275 | struct hlist_node *new) | |
276 | { | |
277 | struct hlist_node *next = old->next; | |
278 | ||
279 | new->next = next; | |
280 | new->pprev = old->pprev; | |
10aa9d2c | 281 | rcu_assign_pointer(*new->pprev, new); |
82524746 FBH |
282 | if (next) |
283 | new->next->pprev = &new->next; | |
82524746 FBH |
284 | old->pprev = LIST_POISON2; |
285 | } | |
286 | ||
287 | /** | |
288 | * hlist_add_head_rcu | |
289 | * @n: the element to add to the hash list. | |
290 | * @h: the list to add to. | |
291 | * | |
292 | * Description: | |
293 | * Adds the specified element to the specified hlist, | |
294 | * while permitting racing traversals. | |
295 | * | |
296 | * The caller must take whatever precautions are necessary | |
297 | * (such as holding appropriate locks) to avoid racing | |
298 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
299 | * or hlist_del_rcu(), running on this same list. | |
300 | * However, it is perfectly legal to run concurrently with | |
301 | * the _rcu list-traversal primitives, such as | |
302 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
303 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
304 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
305 | */ | |
306 | static inline void hlist_add_head_rcu(struct hlist_node *n, | |
307 | struct hlist_head *h) | |
308 | { | |
309 | struct hlist_node *first = h->first; | |
10aa9d2c | 310 | |
82524746 FBH |
311 | n->next = first; |
312 | n->pprev = &h->first; | |
10aa9d2c | 313 | rcu_assign_pointer(h->first, n); |
82524746 FBH |
314 | if (first) |
315 | first->pprev = &n->next; | |
82524746 FBH |
316 | } |
317 | ||
318 | /** | |
319 | * hlist_add_before_rcu | |
320 | * @n: the new element to add to the hash list. | |
321 | * @next: the existing element to add the new element before. | |
322 | * | |
323 | * Description: | |
324 | * Adds the specified element to the specified hlist | |
325 | * before the specified node while permitting racing traversals. | |
326 | * | |
327 | * The caller must take whatever precautions are necessary | |
328 | * (such as holding appropriate locks) to avoid racing | |
329 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
330 | * or hlist_del_rcu(), running on this same list. | |
331 | * However, it is perfectly legal to run concurrently with | |
332 | * the _rcu list-traversal primitives, such as | |
333 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
334 | * problems on Alpha CPUs. | |
335 | */ | |
336 | static inline void hlist_add_before_rcu(struct hlist_node *n, | |
337 | struct hlist_node *next) | |
338 | { | |
339 | n->pprev = next->pprev; | |
340 | n->next = next; | |
10aa9d2c | 341 | rcu_assign_pointer(*(n->pprev), n); |
82524746 | 342 | next->pprev = &n->next; |
82524746 FBH |
343 | } |
344 | ||
345 | /** | |
346 | * hlist_add_after_rcu | |
347 | * @prev: the existing element to add the new element after. | |
348 | * @n: the new element to add to the hash list. | |
349 | * | |
350 | * Description: | |
351 | * Adds the specified element to the specified hlist | |
352 | * after the specified node while permitting racing traversals. | |
353 | * | |
354 | * The caller must take whatever precautions are necessary | |
355 | * (such as holding appropriate locks) to avoid racing | |
356 | * with another list-mutation primitive, such as hlist_add_head_rcu() | |
357 | * or hlist_del_rcu(), running on this same list. | |
358 | * However, it is perfectly legal to run concurrently with | |
359 | * the _rcu list-traversal primitives, such as | |
360 | * hlist_for_each_entry_rcu(), used to prevent memory-consistency | |
361 | * problems on Alpha CPUs. | |
362 | */ | |
363 | static inline void hlist_add_after_rcu(struct hlist_node *prev, | |
364 | struct hlist_node *n) | |
365 | { | |
366 | n->next = prev->next; | |
367 | n->pprev = &prev->next; | |
10aa9d2c | 368 | rcu_assign_pointer(prev->next, n); |
82524746 FBH |
369 | if (n->next) |
370 | n->next->pprev = &n->next; | |
371 | } | |
372 | ||
373 | /** | |
374 | * hlist_for_each_entry_rcu - iterate over rcu list of given type | |
375 | * @tpos: the type * to use as a loop cursor. | |
376 | * @pos: the &struct hlist_node to use as a loop cursor. | |
377 | * @head: the head for your list. | |
378 | * @member: the name of the hlist_node within the struct. | |
379 | * | |
380 | * This list-traversal primitive may safely run concurrently with | |
381 | * the _rcu list-mutation primitives such as hlist_add_head_rcu() | |
382 | * as long as the traversal is guarded by rcu_read_lock(). | |
383 | */ | |
384 | #define hlist_for_each_entry_rcu(tpos, pos, head, member) \ | |
385 | for (pos = (head)->first; \ | |
386 | rcu_dereference(pos) && ({ prefetch(pos->next); 1; }) && \ | |
387 | ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \ | |
388 | pos = pos->next) | |
389 | ||
390 | #endif /* __KERNEL__ */ | |
391 | #endif |