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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. | |
82 | * @k: klist it's going on. | |
83 | * @n: node we're adding. | |
84 | */ | |
85 | ||
86 | void klist_add_head(struct klist * k, struct klist_node * n) | |
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. | |
97 | * @k: klist it's going on. | |
98 | * @n: node we're adding. | |
99 | */ | |
100 | ||
101 | void klist_add_tail(struct klist * k, struct klist_node * n) | |
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); | |
115 | } | |
116 | ||
117 | static int klist_dec_and_del(struct klist_node * n) | |
118 | { | |
119 | return kref_put(&n->n_ref, klist_release); | |
120 | } | |
121 | ||
122 | ||
123 | /** | |
124 | * klist_del - Decrement the reference count of node and try to remove. | |
125 | * @n: node we're deleting. | |
126 | */ | |
127 | ||
128 | void klist_del(struct klist_node * n) | |
129 | { | |
130 | struct klist * k = n->n_klist; | |
131 | ||
132 | spin_lock(&k->k_lock); | |
133 | klist_dec_and_del(n); | |
134 | spin_unlock(&k->k_lock); | |
135 | } | |
136 | ||
137 | EXPORT_SYMBOL_GPL(klist_del); | |
138 | ||
139 | ||
140 | /** | |
141 | * klist_remove - Decrement the refcount of node and wait for it to go away. | |
142 | * @n: node we're removing. | |
143 | */ | |
144 | ||
145 | void klist_remove(struct klist_node * n) | |
146 | { | |
147 | spin_lock(&n->n_klist->k_lock); | |
148 | klist_dec_and_del(n); | |
149 | spin_unlock(&n->n_klist->k_lock); | |
150 | wait_for_completion(&n->n_removed); | |
151 | } | |
152 | ||
153 | EXPORT_SYMBOL_GPL(klist_remove); | |
154 | ||
155 | ||
156 | /** | |
157 | * klist_iter_init_node - Initialize a klist_iter structure. | |
158 | * @k: klist we're iterating. | |
159 | * @i: klist_iter we're filling. | |
160 | * @n: node to start with. | |
161 | * | |
162 | * Similar to klist_iter_init(), but starts the action off with @n, | |
163 | * instead of with the list head. | |
164 | */ | |
165 | ||
166 | void klist_iter_init_node(struct klist * k, struct klist_iter * i, struct klist_node * n) | |
167 | { | |
168 | i->i_klist = k; | |
169 | i->i_head = &k->k_list; | |
170 | i->i_cur = n; | |
171 | } | |
172 | ||
173 | EXPORT_SYMBOL_GPL(klist_iter_init_node); | |
174 | ||
175 | ||
176 | /** | |
177 | * klist_iter_init - Iniitalize a klist_iter structure. | |
178 | * @k: klist we're iterating. | |
179 | * @i: klist_iter structure we're filling. | |
180 | * | |
181 | * Similar to klist_iter_init_node(), but start with the list head. | |
182 | */ | |
183 | ||
184 | void klist_iter_init(struct klist * k, struct klist_iter * i) | |
185 | { | |
186 | klist_iter_init_node(k, i, NULL); | |
187 | } | |
188 | ||
189 | EXPORT_SYMBOL_GPL(klist_iter_init); | |
190 | ||
191 | ||
192 | /** | |
193 | * klist_iter_exit - Finish a list iteration. | |
194 | * @i: Iterator structure. | |
195 | * | |
196 | * Must be called when done iterating over list, as it decrements the | |
197 | * refcount of the current node. Necessary in case iteration exited before | |
198 | * the end of the list was reached, and always good form. | |
199 | */ | |
200 | ||
201 | void klist_iter_exit(struct klist_iter * i) | |
202 | { | |
203 | if (i->i_cur) { | |
204 | klist_del(i->i_cur); | |
205 | i->i_cur = NULL; | |
206 | } | |
207 | } | |
208 | ||
209 | EXPORT_SYMBOL_GPL(klist_iter_exit); | |
210 | ||
211 | ||
212 | static struct klist_node * to_klist_node(struct list_head * n) | |
213 | { | |
214 | return container_of(n, struct klist_node, n_node); | |
215 | } | |
216 | ||
217 | ||
218 | /** | |
219 | * klist_next - Ante up next node in list. | |
220 | * @i: Iterator structure. | |
221 | * | |
222 | * First grab list lock. Decrement the reference count of the previous | |
223 | * node, if there was one. Grab the next node, increment its reference | |
224 | * count, drop the lock, and return that next node. | |
225 | */ | |
226 | ||
227 | struct klist_node * klist_next(struct klist_iter * i) | |
228 | { | |
229 | struct list_head * next; | |
230 | struct klist_node * knode = NULL; | |
231 | ||
232 | spin_lock(&i->i_klist->k_lock); | |
233 | if (i->i_cur) { | |
234 | next = i->i_cur->n_node.next; | |
235 | klist_dec_and_del(i->i_cur); | |
236 | } else | |
237 | next = i->i_head->next; | |
238 | ||
239 | if (next != i->i_head) { | |
240 | knode = to_klist_node(next); | |
241 | kref_get(&knode->n_ref); | |
242 | } | |
243 | i->i_cur = knode; | |
244 | spin_unlock(&i->i_klist->k_lock); | |
245 | return knode; | |
246 | } | |
247 | ||
248 | EXPORT_SYMBOL_GPL(klist_next); |