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git.proxmox.com Git - mirror_ubuntu-zesty-kernel.git/blob - lib/klist.c
2 * klist.c - Routines for manipulating klists.
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
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.
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.
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).
33 * Copyright (C) 2005 Patrick Mochel
35 * This file is released under the GPL v2.
38 #include <linux/klist.h>
39 #include <linux/module.h>
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)
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
55 void klist_init(struct klist
* k
, void (*get
)(struct klist_node
*),
56 void (*put
)(struct klist_node
*))
58 INIT_LIST_HEAD(&k
->k_list
);
59 spin_lock_init(&k
->k_lock
);
64 EXPORT_SYMBOL_GPL(klist_init
);
67 static void add_head(struct klist
* k
, struct klist_node
* n
)
69 spin_lock(&k
->k_lock
);
70 list_add(&n
->n_node
, &k
->k_list
);
71 spin_unlock(&k
->k_lock
);
74 static void add_tail(struct klist
* k
, struct klist_node
* n
)
76 spin_lock(&k
->k_lock
);
77 list_add_tail(&n
->n_node
, &k
->k_list
);
78 spin_unlock(&k
->k_lock
);
82 static void klist_node_init(struct klist
* k
, struct klist_node
* n
)
84 INIT_LIST_HEAD(&n
->n_node
);
85 init_completion(&n
->n_removed
);
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.
99 void klist_add_head(struct klist_node
* n
, struct klist
* k
)
101 klist_node_init(k
, n
);
105 EXPORT_SYMBOL_GPL(klist_add_head
);
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.
114 void klist_add_tail(struct klist_node
* n
, struct klist
* k
)
116 klist_node_init(k
, n
);
120 EXPORT_SYMBOL_GPL(klist_add_tail
);
123 static void klist_release(struct kref
* kref
)
125 struct klist_node
* n
= container_of(kref
, struct klist_node
, n_ref
);
127 list_del(&n
->n_node
);
128 complete(&n
->n_removed
);
132 static int klist_dec_and_del(struct klist_node
* n
)
134 return kref_put(&n
->n_ref
, klist_release
);
139 * klist_del - Decrement the reference count of node and try to remove.
140 * @n: node we're deleting.
143 void klist_del(struct klist_node
* n
)
145 struct klist
* k
= n
->n_klist
;
146 void (*put
)(struct klist_node
*) = k
->put
;
148 spin_lock(&k
->k_lock
);
149 if (!klist_dec_and_del(n
))
151 spin_unlock(&k
->k_lock
);
156 EXPORT_SYMBOL_GPL(klist_del
);
160 * klist_remove - Decrement the refcount of node and wait for it to go away.
161 * @n: node we're removing.
164 void klist_remove(struct klist_node
* n
)
167 wait_for_completion(&n
->n_removed
);
170 EXPORT_SYMBOL_GPL(klist_remove
);
174 * klist_node_attached - Say whether a node is bound to a list or not.
175 * @n: Node that we're testing.
178 int klist_node_attached(struct klist_node
* n
)
180 return (n
->n_klist
!= NULL
);
183 EXPORT_SYMBOL_GPL(klist_node_attached
);
187 * klist_iter_init_node - Initialize a klist_iter structure.
188 * @k: klist we're iterating.
189 * @i: klist_iter we're filling.
190 * @n: node to start with.
192 * Similar to klist_iter_init(), but starts the action off with @n,
193 * instead of with the list head.
196 void klist_iter_init_node(struct klist
* k
, struct klist_iter
* i
, struct klist_node
* n
)
199 i
->i_head
= &k
->k_list
;
205 EXPORT_SYMBOL_GPL(klist_iter_init_node
);
209 * klist_iter_init - Iniitalize a klist_iter structure.
210 * @k: klist we're iterating.
211 * @i: klist_iter structure we're filling.
213 * Similar to klist_iter_init_node(), but start with the list head.
216 void klist_iter_init(struct klist
* k
, struct klist_iter
* i
)
218 klist_iter_init_node(k
, i
, NULL
);
221 EXPORT_SYMBOL_GPL(klist_iter_init
);
225 * klist_iter_exit - Finish a list iteration.
226 * @i: Iterator structure.
228 * Must be called when done iterating over list, as it decrements the
229 * refcount of the current node. Necessary in case iteration exited before
230 * the end of the list was reached, and always good form.
233 void klist_iter_exit(struct klist_iter
* i
)
241 EXPORT_SYMBOL_GPL(klist_iter_exit
);
244 static struct klist_node
* to_klist_node(struct list_head
* n
)
246 return container_of(n
, struct klist_node
, n_node
);
251 * klist_next - Ante up next node in list.
252 * @i: Iterator structure.
254 * First grab list lock. Decrement the reference count of the previous
255 * node, if there was one. Grab the next node, increment its reference
256 * count, drop the lock, and return that next node.
259 struct klist_node
* klist_next(struct klist_iter
* i
)
261 struct list_head
* next
;
262 struct klist_node
* lnode
= i
->i_cur
;
263 struct klist_node
* knode
= NULL
;
264 void (*put
)(struct klist_node
*) = i
->i_klist
->put
;
266 spin_lock(&i
->i_klist
->k_lock
);
268 next
= lnode
->n_node
.next
;
269 if (!klist_dec_and_del(lnode
))
272 next
= i
->i_head
->next
;
274 if (next
!= i
->i_head
) {
275 knode
= to_klist_node(next
);
276 kref_get(&knode
->n_ref
);
279 spin_unlock(&i
->i_klist
->k_lock
);
285 EXPORT_SYMBOL_GPL(klist_next
);