tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 * @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.
53 */
54
55void klist_init(struct klist * k, void (*get)(struct klist_node *),
56 void (*put)(struct klist_node *))
57{
58 INIT_LIST_HEAD(&k->k_list);
59 spin_lock_init(&k->k_lock);
60 k->get = get;
61 k->put = put;
62}
63
64EXPORT_SYMBOL_GPL(klist_init);
65
66
67static 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
74static 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
82static 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;
88 if (k->get)
89 k->get(n);
90}
91
92
93/**
94 * klist_add_head - Initialize a klist_node and add it to front.
95 * @n: node we're adding.
96 * @k: klist it's going on.
97 */
98
99void klist_add_head(struct klist_node * n, struct klist * k)
100{
101 klist_node_init(k, n);
102 add_head(k, n);
103}
104
105EXPORT_SYMBOL_GPL(klist_add_head);
106
107
108/**
109 * klist_add_tail - Initialize a klist_node and add it to back.
110 * @n: node we're adding.
111 * @k: klist it's going on.
112 */
113
114void klist_add_tail(struct klist_node * n, struct klist * k)
115{
116 klist_node_init(k, n);
117 add_tail(k, n);
118}
119
120EXPORT_SYMBOL_GPL(klist_add_tail);
121
122
123static void klist_release(struct kref * kref)
124{
125 struct klist_node * n = container_of(kref, struct klist_node, n_ref);
126 void (*put)(struct klist_node *) = n->n_klist->put;
127 list_del(&n->n_node);
128 complete(&n->n_removed);
129 n->n_klist = NULL;
130 if (put)
131 put(n);
132}
133
134static 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
145void 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
154EXPORT_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
162void klist_remove(struct klist_node * n)
163{
164 struct klist * k = n->n_klist;
165 spin_lock(&k->k_lock);
166 klist_dec_and_del(n);
167 spin_unlock(&k->k_lock);
168 wait_for_completion(&n->n_removed);
169}
170
171EXPORT_SYMBOL_GPL(klist_remove);
172
173
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
179int klist_node_attached(struct klist_node * n)
180{
181 return (n->n_klist != NULL);
182}
183
184EXPORT_SYMBOL_GPL(klist_node_attached);
185
186
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
197void 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;
202}
203
204EXPORT_SYMBOL_GPL(klist_iter_init_node);
205
206
207/**
208 * klist_iter_init - Iniitalize a klist_iter structure.
209 * @k: klist we're iterating.
210 * @i: klist_iter structure we're filling.
211 *
212 * Similar to klist_iter_init_node(), but start with the list head.
213 */
214
215void klist_iter_init(struct klist * k, struct klist_iter * i)
216{
217 klist_iter_init_node(k, i, NULL);
218}
219
220EXPORT_SYMBOL_GPL(klist_iter_init);
221
222
223/**
224 * klist_iter_exit - Finish a list iteration.
225 * @i: Iterator structure.
226 *
227 * Must be called when done iterating over list, as it decrements the
228 * refcount of the current node. Necessary in case iteration exited before
229 * the end of the list was reached, and always good form.
230 */
231
232void klist_iter_exit(struct klist_iter * i)
233{
234 if (i->i_cur) {
235 klist_del(i->i_cur);
236 i->i_cur = NULL;
237 }
238}
239
240EXPORT_SYMBOL_GPL(klist_iter_exit);
241
242
243static struct klist_node * to_klist_node(struct list_head * n)
244{
245 return container_of(n, struct klist_node, n_node);
246}
247
248
249/**
250 * klist_next - Ante up next node in list.
251 * @i: Iterator structure.
252 *
253 * First grab list lock. Decrement the reference count of the previous
254 * node, if there was one. Grab the next node, increment its reference
255 * count, drop the lock, and return that next node.
256 */
257
258struct klist_node * klist_next(struct klist_iter * i)
259{
260 struct list_head * next;
261 struct klist_node * knode = NULL;
262
263 spin_lock(&i->i_klist->k_lock);
264 if (i->i_cur) {
265 next = i->i_cur->n_node.next;
266 klist_dec_and_del(i->i_cur);
267 } else
268 next = i->i_head->next;
269
270 if (next != i->i_head) {
271 knode = to_klist_node(next);
272 kref_get(&knode->n_ref);
273 }
274 i->i_cur = knode;
275 spin_unlock(&i->i_klist->k_lock);
276 return knode;
277}
278
279EXPORT_SYMBOL_GPL(klist_next);
280
281