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9a19fea4 PM |
1 | /* |
2 | * klist.c - Routines for manipulating klists. | |
3 | * | |
4 | * | |
5 | * This klist interface provides a couple of structures that wrap around | |
6 | * struct list_head to provide explicit list "head" (struct klist) and | |
7 | * list "node" (struct klist_node) objects. For struct klist, a spinlock | |
8 | * is included that protects access to the actual list itself. struct | |
9 | * klist_node provides a pointer to the klist that owns it and a kref | |
10 | * reference count that indicates the number of current users of that node | |
11 | * in the list. | |
12 | * | |
13 | * The entire point is to provide an interface for iterating over a list | |
14 | * that is safe and allows for modification of the list during the | |
15 | * iteration (e.g. insertion and removal), including modification of the | |
16 | * current node on the list. | |
17 | * | |
18 | * It works using a 3rd object type - struct klist_iter - that is declared | |
19 | * and initialized before an iteration. klist_next() is used to acquire the | |
20 | * next element in the list. It returns NULL if there are no more items. | |
21 | * Internally, that routine takes the klist's lock, decrements the reference | |
22 | * count of the previous klist_node and increments the count of the next | |
23 | * klist_node. It then drops the lock and returns. | |
24 | * | |
25 | * There are primitives for adding and removing nodes to/from a klist. | |
26 | * When deleting, klist_del() will simply decrement the reference count. | |
27 | * Only when the count goes to 0 is the node removed from the list. | |
28 | * klist_remove() will try to delete the node from the list and block | |
29 | * until it is actually removed. This is useful for objects (like devices) | |
30 | * that have been removed from the system and must be freed (but must wait | |
31 | * until all accessors have finished). | |
32 | * | |
33 | * Copyright (C) 2005 Patrick Mochel | |
34 | * | |
35 | * This file is released under the GPL v2. | |
36 | */ | |
37 | ||
38 | #include <linux/klist.h> | |
39 | #include <linux/module.h> | |
40 | ||
41 | ||
42 | /** | |
43 | * klist_init - Initialize a klist structure. | |
44 | * @k: The klist we're initializing. | |
34bb61f9 JB |
45 | * @get: The get function for the embedding object (NULL if none) |
46 | * @put: The put function for the embedding object (NULL if none) | |
47 | * | |
48 | * Initialises the klist structure. If the klist_node structures are | |
49 | * going to be embedded in refcounted objects (necessary for safe | |
50 | * deletion) then the get/put arguments are used to initialise | |
51 | * functions that take and release references on the embedding | |
52 | * objects. | |
9a19fea4 PM |
53 | */ |
54 | ||
34bb61f9 JB |
55 | void klist_init(struct klist * k, void (*get)(struct klist_node *), |
56 | void (*put)(struct klist_node *)) | |
9a19fea4 PM |
57 | { |
58 | INIT_LIST_HEAD(&k->k_list); | |
59 | spin_lock_init(&k->k_lock); | |
34bb61f9 JB |
60 | k->get = get; |
61 | k->put = put; | |
9a19fea4 PM |
62 | } |
63 | ||
64 | EXPORT_SYMBOL_GPL(klist_init); | |
65 | ||
66 | ||
67 | static void add_head(struct klist * k, struct klist_node * n) | |
68 | { | |
69 | spin_lock(&k->k_lock); | |
70 | list_add(&n->n_node, &k->k_list); | |
71 | spin_unlock(&k->k_lock); | |
72 | } | |
73 | ||
74 | static void add_tail(struct klist * k, struct klist_node * n) | |
75 | { | |
76 | spin_lock(&k->k_lock); | |
77 | list_add_tail(&n->n_node, &k->k_list); | |
78 | spin_unlock(&k->k_lock); | |
79 | } | |
80 | ||
81 | ||
82 | static void klist_node_init(struct klist * k, struct klist_node * n) | |
83 | { | |
84 | INIT_LIST_HEAD(&n->n_node); | |
85 | init_completion(&n->n_removed); | |
86 | kref_init(&n->n_ref); | |
87 | n->n_klist = k; | |
34bb61f9 JB |
88 | if (k->get) |
89 | k->get(n); | |
9a19fea4 PM |
90 | } |
91 | ||
92 | ||
93 | /** | |
94 | * klist_add_head - Initialize a klist_node and add it to front. | |
9a19fea4 | 95 | * @n: node we're adding. |
d856f1e3 | 96 | * @k: klist it's going on. |
9a19fea4 PM |
97 | */ |
98 | ||
d856f1e3 | 99 | void klist_add_head(struct klist_node * n, struct klist * k) |
9a19fea4 PM |
100 | { |
101 | klist_node_init(k, n); | |
102 | add_head(k, n); | |
103 | } | |
104 | ||
105 | EXPORT_SYMBOL_GPL(klist_add_head); | |
106 | ||
107 | ||
108 | /** | |
109 | * klist_add_tail - Initialize a klist_node and add it to back. | |
9a19fea4 | 110 | * @n: node we're adding. |
d856f1e3 | 111 | * @k: klist it's going on. |
9a19fea4 PM |
112 | */ |
113 | ||
d856f1e3 | 114 | void klist_add_tail(struct klist_node * n, struct klist * k) |
9a19fea4 PM |
115 | { |
116 | klist_node_init(k, n); | |
117 | add_tail(k, n); | |
118 | } | |
119 | ||
120 | EXPORT_SYMBOL_GPL(klist_add_tail); | |
121 | ||
122 | ||
123 | static void klist_release(struct kref * kref) | |
124 | { | |
125 | struct klist_node * n = container_of(kref, struct klist_node, n_ref); | |
34bb61f9 | 126 | void (*put)(struct klist_node *) = n->n_klist->put; |
9a19fea4 PM |
127 | list_del(&n->n_node); |
128 | complete(&n->n_removed); | |
8b0c250b | 129 | n->n_klist = NULL; |
34bb61f9 JB |
130 | if (put) |
131 | put(n); | |
9a19fea4 PM |
132 | } |
133 | ||
134 | static int klist_dec_and_del(struct klist_node * n) | |
135 | { | |
136 | return kref_put(&n->n_ref, klist_release); | |
137 | } | |
138 | ||
139 | ||
140 | /** | |
141 | * klist_del - Decrement the reference count of node and try to remove. | |
142 | * @n: node we're deleting. | |
143 | */ | |
144 | ||
145 | void klist_del(struct klist_node * n) | |
146 | { | |
147 | struct klist * k = n->n_klist; | |
148 | ||
149 | spin_lock(&k->k_lock); | |
150 | klist_dec_and_del(n); | |
151 | spin_unlock(&k->k_lock); | |
152 | } | |
153 | ||
154 | EXPORT_SYMBOL_GPL(klist_del); | |
155 | ||
156 | ||
157 | /** | |
158 | * klist_remove - Decrement the refcount of node and wait for it to go away. | |
159 | * @n: node we're removing. | |
160 | */ | |
161 | ||
162 | void klist_remove(struct klist_node * n) | |
163 | { | |
0293a509 PM |
164 | struct klist * k = n->n_klist; |
165 | spin_lock(&k->k_lock); | |
9a19fea4 | 166 | klist_dec_and_del(n); |
0293a509 | 167 | spin_unlock(&k->k_lock); |
9a19fea4 PM |
168 | wait_for_completion(&n->n_removed); |
169 | } | |
170 | ||
171 | EXPORT_SYMBOL_GPL(klist_remove); | |
172 | ||
173 | ||
8b0c250b PM |
174 | /** |
175 | * klist_node_attached - Say whether a node is bound to a list or not. | |
176 | * @n: Node that we're testing. | |
177 | */ | |
178 | ||
179 | int klist_node_attached(struct klist_node * n) | |
180 | { | |
181 | return (n->n_klist != NULL); | |
182 | } | |
183 | ||
184 | EXPORT_SYMBOL_GPL(klist_node_attached); | |
185 | ||
186 | ||
9a19fea4 PM |
187 | /** |
188 | * klist_iter_init_node - Initialize a klist_iter structure. | |
189 | * @k: klist we're iterating. | |
190 | * @i: klist_iter we're filling. | |
191 | * @n: node to start with. | |
192 | * | |
193 | * Similar to klist_iter_init(), but starts the action off with @n, | |
194 | * instead of with the list head. | |
195 | */ | |
196 | ||
197 | void klist_iter_init_node(struct klist * k, struct klist_iter * i, struct klist_node * n) | |
198 | { | |
199 | i->i_klist = k; | |
200 | i->i_head = &k->k_list; | |
201 | i->i_cur = n; | |
e22dafbc FP |
202 | if (n) |
203 | kref_get(&n->n_ref); | |
9a19fea4 PM |
204 | } |
205 | ||
206 | EXPORT_SYMBOL_GPL(klist_iter_init_node); | |
207 | ||
208 | ||
209 | /** | |
210 | * klist_iter_init - Iniitalize a klist_iter structure. | |
211 | * @k: klist we're iterating. | |
212 | * @i: klist_iter structure we're filling. | |
213 | * | |
214 | * Similar to klist_iter_init_node(), but start with the list head. | |
215 | */ | |
216 | ||
217 | void klist_iter_init(struct klist * k, struct klist_iter * i) | |
218 | { | |
219 | klist_iter_init_node(k, i, NULL); | |
220 | } | |
221 | ||
222 | EXPORT_SYMBOL_GPL(klist_iter_init); | |
223 | ||
224 | ||
225 | /** | |
226 | * klist_iter_exit - Finish a list iteration. | |
227 | * @i: Iterator structure. | |
228 | * | |
229 | * Must be called when done iterating over list, as it decrements the | |
230 | * refcount of the current node. Necessary in case iteration exited before | |
231 | * the end of the list was reached, and always good form. | |
232 | */ | |
233 | ||
234 | void klist_iter_exit(struct klist_iter * i) | |
235 | { | |
236 | if (i->i_cur) { | |
237 | klist_del(i->i_cur); | |
238 | i->i_cur = NULL; | |
239 | } | |
240 | } | |
241 | ||
242 | EXPORT_SYMBOL_GPL(klist_iter_exit); | |
243 | ||
244 | ||
245 | static struct klist_node * to_klist_node(struct list_head * n) | |
246 | { | |
247 | return container_of(n, struct klist_node, n_node); | |
248 | } | |
249 | ||
250 | ||
251 | /** | |
252 | * klist_next - Ante up next node in list. | |
253 | * @i: Iterator structure. | |
254 | * | |
255 | * First grab list lock. Decrement the reference count of the previous | |
256 | * node, if there was one. Grab the next node, increment its reference | |
257 | * count, drop the lock, and return that next node. | |
258 | */ | |
259 | ||
260 | struct klist_node * klist_next(struct klist_iter * i) | |
261 | { | |
262 | struct list_head * next; | |
263 | struct klist_node * knode = NULL; | |
264 | ||
265 | spin_lock(&i->i_klist->k_lock); | |
266 | if (i->i_cur) { | |
267 | next = i->i_cur->n_node.next; | |
268 | klist_dec_and_del(i->i_cur); | |
269 | } else | |
270 | next = i->i_head->next; | |
271 | ||
272 | if (next != i->i_head) { | |
273 | knode = to_klist_node(next); | |
274 | kref_get(&knode->n_ref); | |
275 | } | |
276 | i->i_cur = knode; | |
277 | spin_unlock(&i->i_klist->k_lock); | |
278 | return knode; | |
279 | } | |
280 | ||
281 | EXPORT_SYMBOL_GPL(klist_next); | |
8b0c250b PM |
282 | |
283 |