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 */
46
47void klist_init(struct klist * k)
48{
49 INIT_LIST_HEAD(&k->k_list);
50 spin_lock_init(&k->k_lock);
51}
52
53EXPORT_SYMBOL_GPL(klist_init);
54
55
56static 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
63static 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
71static 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
86void klist_add_head(struct klist * k, struct klist_node * n)
87{
88 klist_node_init(k, n);
89 add_head(k, n);
90}
91
92EXPORT_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
101void klist_add_tail(struct klist * k, struct klist_node * n)
102{
103 klist_node_init(k, n);
104 add_tail(k, n);
105}
106
107EXPORT_SYMBOL_GPL(klist_add_tail);
108
109
110static 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 n->n_klist = NULL;
116}
117
118static 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
129void 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
138EXPORT_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
146void klist_remove(struct klist_node * n)
147{
148 struct klist * k = n->n_klist;
149 spin_lock(&k->k_lock);
150 klist_dec_and_del(n);
151 spin_unlock(&k->k_lock);
152 wait_for_completion(&n->n_removed);
153}
154
155EXPORT_SYMBOL_GPL(klist_remove);
156
157
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
163int klist_node_attached(struct klist_node * n)
164{
165 return (n->n_klist != NULL);
166}
167
168EXPORT_SYMBOL_GPL(klist_node_attached);
169
170
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
181void 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
188EXPORT_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
199void klist_iter_init(struct klist * k, struct klist_iter * i)
200{
201 klist_iter_init_node(k, i, NULL);
202}
203
204EXPORT_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
216void 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
224EXPORT_SYMBOL_GPL(klist_iter_exit);
225
226
227static 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
242struct 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
263EXPORT_SYMBOL_GPL(klist_next);
264
265