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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. | |
45 | */ | |
46 | ||
47 | void klist_init(struct klist * k) | |
48 | { | |
49 | INIT_LIST_HEAD(&k->k_list); | |
50 | spin_lock_init(&k->k_lock); | |
51 | } | |
52 | ||
53 | EXPORT_SYMBOL_GPL(klist_init); | |
54 | ||
55 | ||
56 | static void add_head(struct klist * k, struct klist_node * n) | |
57 | { | |
58 | spin_lock(&k->k_lock); | |
59 | list_add(&n->n_node, &k->k_list); | |
60 | spin_unlock(&k->k_lock); | |
61 | } | |
62 | ||
63 | static void add_tail(struct klist * k, struct klist_node * n) | |
64 | { | |
65 | spin_lock(&k->k_lock); | |
66 | list_add_tail(&n->n_node, &k->k_list); | |
67 | spin_unlock(&k->k_lock); | |
68 | } | |
69 | ||
70 | ||
71 | static void klist_node_init(struct klist * k, struct klist_node * n) | |
72 | { | |
73 | INIT_LIST_HEAD(&n->n_node); | |
74 | init_completion(&n->n_removed); | |
75 | kref_init(&n->n_ref); | |
76 | n->n_klist = k; | |
77 | } | |
78 | ||
79 | ||
80 | /** | |
81 | * klist_add_head - Initialize a klist_node and add it to front. | |
9a19fea4 | 82 | * @n: node we're adding. |
d856f1e3 | 83 | * @k: klist it's going on. |
9a19fea4 PM |
84 | */ |
85 | ||
d856f1e3 | 86 | void klist_add_head(struct klist_node * n, struct klist * k) |
9a19fea4 PM |
87 | { |
88 | klist_node_init(k, n); | |
89 | add_head(k, n); | |
90 | } | |
91 | ||
92 | EXPORT_SYMBOL_GPL(klist_add_head); | |
93 | ||
94 | ||
95 | /** | |
96 | * klist_add_tail - Initialize a klist_node and add it to back. | |
9a19fea4 | 97 | * @n: node we're adding. |
d856f1e3 | 98 | * @k: klist it's going on. |
9a19fea4 PM |
99 | */ |
100 | ||
d856f1e3 | 101 | void klist_add_tail(struct klist_node * n, struct klist * k) |
9a19fea4 PM |
102 | { |
103 | klist_node_init(k, n); | |
104 | add_tail(k, n); | |
105 | } | |
106 | ||
107 | EXPORT_SYMBOL_GPL(klist_add_tail); | |
108 | ||
109 | ||
110 | static void klist_release(struct kref * kref) | |
111 | { | |
112 | struct klist_node * n = container_of(kref, struct klist_node, n_ref); | |
113 | list_del(&n->n_node); | |
114 | complete(&n->n_removed); | |
8b0c250b | 115 | n->n_klist = NULL; |
9a19fea4 PM |
116 | } |
117 | ||
118 | static int klist_dec_and_del(struct klist_node * n) | |
119 | { | |
120 | return kref_put(&n->n_ref, klist_release); | |
121 | } | |
122 | ||
123 | ||
124 | /** | |
125 | * klist_del - Decrement the reference count of node and try to remove. | |
126 | * @n: node we're deleting. | |
127 | */ | |
128 | ||
129 | void klist_del(struct klist_node * n) | |
130 | { | |
131 | struct klist * k = n->n_klist; | |
132 | ||
133 | spin_lock(&k->k_lock); | |
134 | klist_dec_and_del(n); | |
135 | spin_unlock(&k->k_lock); | |
136 | } | |
137 | ||
138 | EXPORT_SYMBOL_GPL(klist_del); | |
139 | ||
140 | ||
141 | /** | |
142 | * klist_remove - Decrement the refcount of node and wait for it to go away. | |
143 | * @n: node we're removing. | |
144 | */ | |
145 | ||
146 | void klist_remove(struct klist_node * n) | |
147 | { | |
0293a509 PM |
148 | struct klist * k = n->n_klist; |
149 | spin_lock(&k->k_lock); | |
9a19fea4 | 150 | klist_dec_and_del(n); |
0293a509 | 151 | spin_unlock(&k->k_lock); |
9a19fea4 PM |
152 | wait_for_completion(&n->n_removed); |
153 | } | |
154 | ||
155 | EXPORT_SYMBOL_GPL(klist_remove); | |
156 | ||
157 | ||
8b0c250b PM |
158 | /** |
159 | * klist_node_attached - Say whether a node is bound to a list or not. | |
160 | * @n: Node that we're testing. | |
161 | */ | |
162 | ||
163 | int klist_node_attached(struct klist_node * n) | |
164 | { | |
165 | return (n->n_klist != NULL); | |
166 | } | |
167 | ||
168 | EXPORT_SYMBOL_GPL(klist_node_attached); | |
169 | ||
170 | ||
9a19fea4 PM |
171 | /** |
172 | * klist_iter_init_node - Initialize a klist_iter structure. | |
173 | * @k: klist we're iterating. | |
174 | * @i: klist_iter we're filling. | |
175 | * @n: node to start with. | |
176 | * | |
177 | * Similar to klist_iter_init(), but starts the action off with @n, | |
178 | * instead of with the list head. | |
179 | */ | |
180 | ||
181 | void klist_iter_init_node(struct klist * k, struct klist_iter * i, struct klist_node * n) | |
182 | { | |
183 | i->i_klist = k; | |
184 | i->i_head = &k->k_list; | |
185 | i->i_cur = n; | |
186 | } | |
187 | ||
188 | EXPORT_SYMBOL_GPL(klist_iter_init_node); | |
189 | ||
190 | ||
191 | /** | |
192 | * klist_iter_init - Iniitalize a klist_iter structure. | |
193 | * @k: klist we're iterating. | |
194 | * @i: klist_iter structure we're filling. | |
195 | * | |
196 | * Similar to klist_iter_init_node(), but start with the list head. | |
197 | */ | |
198 | ||
199 | void klist_iter_init(struct klist * k, struct klist_iter * i) | |
200 | { | |
201 | klist_iter_init_node(k, i, NULL); | |
202 | } | |
203 | ||
204 | EXPORT_SYMBOL_GPL(klist_iter_init); | |
205 | ||
206 | ||
207 | /** | |
208 | * klist_iter_exit - Finish a list iteration. | |
209 | * @i: Iterator structure. | |
210 | * | |
211 | * Must be called when done iterating over list, as it decrements the | |
212 | * refcount of the current node. Necessary in case iteration exited before | |
213 | * the end of the list was reached, and always good form. | |
214 | */ | |
215 | ||
216 | void klist_iter_exit(struct klist_iter * i) | |
217 | { | |
218 | if (i->i_cur) { | |
219 | klist_del(i->i_cur); | |
220 | i->i_cur = NULL; | |
221 | } | |
222 | } | |
223 | ||
224 | EXPORT_SYMBOL_GPL(klist_iter_exit); | |
225 | ||
226 | ||
227 | static struct klist_node * to_klist_node(struct list_head * n) | |
228 | { | |
229 | return container_of(n, struct klist_node, n_node); | |
230 | } | |
231 | ||
232 | ||
233 | /** | |
234 | * klist_next - Ante up next node in list. | |
235 | * @i: Iterator structure. | |
236 | * | |
237 | * First grab list lock. Decrement the reference count of the previous | |
238 | * node, if there was one. Grab the next node, increment its reference | |
239 | * count, drop the lock, and return that next node. | |
240 | */ | |
241 | ||
242 | struct klist_node * klist_next(struct klist_iter * i) | |
243 | { | |
244 | struct list_head * next; | |
245 | struct klist_node * knode = NULL; | |
246 | ||
247 | spin_lock(&i->i_klist->k_lock); | |
248 | if (i->i_cur) { | |
249 | next = i->i_cur->n_node.next; | |
250 | klist_dec_and_del(i->i_cur); | |
251 | } else | |
252 | next = i->i_head->next; | |
253 | ||
254 | if (next != i->i_head) { | |
255 | knode = to_klist_node(next); | |
256 | kref_get(&knode->n_ref); | |
257 | } | |
258 | i->i_cur = knode; | |
259 | spin_unlock(&i->i_klist->k_lock); | |
260 | return knode; | |
261 | } | |
262 | ||
263 | EXPORT_SYMBOL_GPL(klist_next); | |
8b0c250b PM |
264 | |
265 |