--- /dev/null
+/*
+ * klist.c - Routines for manipulating klists.
+ *
+ *
+ * This klist interface provides a couple of structures that wrap around
+ * struct list_head to provide explicit list "head" (struct klist) and
+ * list "node" (struct klist_node) objects. For struct klist, a spinlock
+ * is included that protects access to the actual list itself. struct
+ * klist_node provides a pointer to the klist that owns it and a kref
+ * reference count that indicates the number of current users of that node
+ * in the list.
+ *
+ * The entire point is to provide an interface for iterating over a list
+ * that is safe and allows for modification of the list during the
+ * iteration (e.g. insertion and removal), including modification of the
+ * current node on the list.
+ *
+ * It works using a 3rd object type - struct klist_iter - that is declared
+ * and initialized before an iteration. klist_next() is used to acquire the
+ * next element in the list. It returns NULL if there are no more items.
+ * Internally, that routine takes the klist's lock, decrements the reference
+ * count of the previous klist_node and increments the count of the next
+ * klist_node. It then drops the lock and returns.
+ *
+ * There are primitives for adding and removing nodes to/from a klist.
+ * When deleting, klist_del() will simply decrement the reference count.
+ * Only when the count goes to 0 is the node removed from the list.
+ * klist_remove() will try to delete the node from the list and block
+ * until it is actually removed. This is useful for objects (like devices)
+ * that have been removed from the system and must be freed (but must wait
+ * until all accessors have finished).
+ *
+ * Copyright (C) 2005 Patrick Mochel
+ *
+ * This file is released under the GPL v2.
+ */
+
+#include <linux/klist.h>
+#include <linux/module.h>
+
+
+/**
+ * klist_init - Initialize a klist structure.
+ * @k: The klist we're initializing.
+ */
+
+void klist_init(struct klist * k)
+{
+ INIT_LIST_HEAD(&k->k_list);
+ spin_lock_init(&k->k_lock);
+}
+
+EXPORT_SYMBOL_GPL(klist_init);
+
+
+static void add_head(struct klist * k, struct klist_node * n)
+{
+ spin_lock(&k->k_lock);
+ list_add(&n->n_node, &k->k_list);
+ spin_unlock(&k->k_lock);
+}
+
+static void add_tail(struct klist * k, struct klist_node * n)
+{
+ spin_lock(&k->k_lock);
+ list_add_tail(&n->n_node, &k->k_list);
+ spin_unlock(&k->k_lock);
+}
+
+
+static void klist_node_init(struct klist * k, struct klist_node * n)
+{
+ INIT_LIST_HEAD(&n->n_node);
+ init_completion(&n->n_removed);
+ kref_init(&n->n_ref);
+ n->n_klist = k;
+}
+
+
+/**
+ * klist_add_head - Initialize a klist_node and add it to front.
+ * @k: klist it's going on.
+ * @n: node we're adding.
+ */
+
+void klist_add_head(struct klist * k, struct klist_node * n)
+{
+ klist_node_init(k, n);
+ add_head(k, n);
+}
+
+EXPORT_SYMBOL_GPL(klist_add_head);
+
+
+/**
+ * klist_add_tail - Initialize a klist_node and add it to back.
+ * @k: klist it's going on.
+ * @n: node we're adding.
+ */
+
+void klist_add_tail(struct klist * k, struct klist_node * n)
+{
+ klist_node_init(k, n);
+ add_tail(k, n);
+}
+
+EXPORT_SYMBOL_GPL(klist_add_tail);
+
+
+static void klist_release(struct kref * kref)
+{
+ struct klist_node * n = container_of(kref, struct klist_node, n_ref);
+ list_del(&n->n_node);
+ complete(&n->n_removed);
+}
+
+static int klist_dec_and_del(struct klist_node * n)
+{
+ return kref_put(&n->n_ref, klist_release);
+}
+
+
+/**
+ * klist_del - Decrement the reference count of node and try to remove.
+ * @n: node we're deleting.
+ */
+
+void klist_del(struct klist_node * n)
+{
+ struct klist * k = n->n_klist;
+
+ spin_lock(&k->k_lock);
+ klist_dec_and_del(n);
+ spin_unlock(&k->k_lock);
+}
+
+EXPORT_SYMBOL_GPL(klist_del);
+
+
+/**
+ * klist_remove - Decrement the refcount of node and wait for it to go away.
+ * @n: node we're removing.
+ */
+
+void klist_remove(struct klist_node * n)
+{
+ spin_lock(&n->n_klist->k_lock);
+ klist_dec_and_del(n);
+ spin_unlock(&n->n_klist->k_lock);
+ wait_for_completion(&n->n_removed);
+}
+
+EXPORT_SYMBOL_GPL(klist_remove);
+
+
+/**
+ * klist_iter_init_node - Initialize a klist_iter structure.
+ * @k: klist we're iterating.
+ * @i: klist_iter we're filling.
+ * @n: node to start with.
+ *
+ * Similar to klist_iter_init(), but starts the action off with @n,
+ * instead of with the list head.
+ */
+
+void klist_iter_init_node(struct klist * k, struct klist_iter * i, struct klist_node * n)
+{
+ i->i_klist = k;
+ i->i_head = &k->k_list;
+ i->i_cur = n;
+}
+
+EXPORT_SYMBOL_GPL(klist_iter_init_node);
+
+
+/**
+ * klist_iter_init - Iniitalize a klist_iter structure.
+ * @k: klist we're iterating.
+ * @i: klist_iter structure we're filling.
+ *
+ * Similar to klist_iter_init_node(), but start with the list head.
+ */
+
+void klist_iter_init(struct klist * k, struct klist_iter * i)
+{
+ klist_iter_init_node(k, i, NULL);
+}
+
+EXPORT_SYMBOL_GPL(klist_iter_init);
+
+
+/**
+ * klist_iter_exit - Finish a list iteration.
+ * @i: Iterator structure.
+ *
+ * Must be called when done iterating over list, as it decrements the
+ * refcount of the current node. Necessary in case iteration exited before
+ * the end of the list was reached, and always good form.
+ */
+
+void klist_iter_exit(struct klist_iter * i)
+{
+ if (i->i_cur) {
+ klist_del(i->i_cur);
+ i->i_cur = NULL;
+ }
+}
+
+EXPORT_SYMBOL_GPL(klist_iter_exit);
+
+
+static struct klist_node * to_klist_node(struct list_head * n)
+{
+ return container_of(n, struct klist_node, n_node);
+}
+
+
+/**
+ * klist_next - Ante up next node in list.
+ * @i: Iterator structure.
+ *
+ * First grab list lock. Decrement the reference count of the previous
+ * node, if there was one. Grab the next node, increment its reference
+ * count, drop the lock, and return that next node.
+ */
+
+struct klist_node * klist_next(struct klist_iter * i)
+{
+ struct list_head * next;
+ struct klist_node * knode = NULL;
+
+ spin_lock(&i->i_klist->k_lock);
+ if (i->i_cur) {
+ next = i->i_cur->n_node.next;
+ klist_dec_and_del(i->i_cur);
+ } else
+ next = i->i_head->next;
+
+ if (next != i->i_head) {
+ knode = to_klist_node(next);
+ kref_get(&knode->n_ref);
+ }
+ i->i_cur = knode;
+ spin_unlock(&i->i_klist->k_lock);
+ return knode;
+}
+
+EXPORT_SYMBOL_GPL(klist_next);
projects / firefly-linux-kernel-4.4.55.git / blobdiff