/*
- * klist.c - Routines for manipulating klists.
+ * klist.c - Routines for manipulating klists.
*
+ * Copyright (C) 2005 Patrick Mochel
*
- * 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.
+ * This file is released under the GPL v2.
*
- * 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.
+ * 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.
*
- * 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.
+ * 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.
*
- * 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).
+ * 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.
*
- * Copyright (C) 2005 Patrick Mochel
- *
- * This file is released under the GPL v2.
+ * 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).
*/
#include <linux/klist.h>
#include <linux/module.h>
+#include <linux/sched.h>
+
+/*
+ * Use the lowest bit of n_klist to mark deleted nodes and exclude
+ * dead ones from iteration.
+ */
+#define KNODE_DEAD 1LU
+#define KNODE_KLIST_MASK ~KNODE_DEAD
+static struct klist *knode_klist(struct klist_node *knode)
+{
+ return (struct klist *)
+ ((unsigned long)knode->n_klist & KNODE_KLIST_MASK);
+}
+
+static bool knode_dead(struct klist_node *knode)
+{
+ return (unsigned long)knode->n_klist & KNODE_DEAD;
+}
+
+static void knode_set_klist(struct klist_node *knode, struct klist *klist)
+{
+ knode->n_klist = klist;
+ /* no knode deserves to start its life dead */
+ WARN_ON(knode_dead(knode));
+}
+
+static void knode_kill(struct klist_node *knode)
+{
+ /* and no knode should die twice ever either, see we're very humane */
+ WARN_ON(knode_dead(knode));
+ *(unsigned long *)&knode->n_klist |= KNODE_DEAD;
+}
/**
- * klist_init - Initialize a klist structure.
- * @k: The klist we're initializing.
+ * klist_init - Initialize a klist structure.
+ * @k: The klist we're initializing.
+ * @get: The get function for the embedding object (NULL if none)
+ * @put: The put function for the embedding object (NULL if none)
+ *
+ * Initialises the klist structure. If the klist_node structures are
+ * going to be embedded in refcounted objects (necessary for safe
+ * deletion) then the get/put arguments are used to initialise
+ * functions that take and release references on the embedding
+ * objects.
*/
-
-void klist_init(struct klist * k)
+void klist_init(struct klist *k, void (*get)(struct klist_node *),
+ void (*put)(struct klist_node *))
{
INIT_LIST_HEAD(&k->k_list);
spin_lock_init(&k->k_lock);
+ k->get = get;
+ k->put = put;
}
-
EXPORT_SYMBOL_GPL(klist_init);
-
-static void add_head(struct klist * k, struct klist_node * n)
+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)
+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)
+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;
+ knode_set_klist(n, k);
+ if (k->get)
+ k->get(n);
}
-
/**
- * klist_add_head - Initialize a klist_node and add it to front.
- * @n: node we're adding.
- * @k: klist it's going on.
+ * klist_add_head - Initialize a klist_node and add it to front.
+ * @n: node we're adding.
+ * @k: klist it's going on.
*/
-
-void klist_add_head(struct klist_node * n, struct klist * k)
+void klist_add_head(struct klist_node *n, struct klist *k)
{
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.
+ * @n: node we're adding.
+ * @k: klist it's going on.
+ */
+void klist_add_tail(struct klist_node *n, struct klist *k)
+{
+ klist_node_init(k, n);
+ add_tail(k, n);
+}
+EXPORT_SYMBOL_GPL(klist_add_tail);
/**
- * klist_add_tail - Initialize a klist_node and add it to back.
- * @n: node we're adding.
- * @k: klist it's going on.
+ * klist_add_after - Init a klist_node and add it after an existing node
+ * @n: node we're adding.
+ * @pos: node to put @n after
*/
+void klist_add_after(struct klist_node *n, struct klist_node *pos)
+{
+ struct klist *k = knode_klist(pos);
-void klist_add_tail(struct klist_node * n, struct klist * k)
+ klist_node_init(k, n);
+ spin_lock(&k->k_lock);
+ list_add(&n->n_node, &pos->n_node);
+ spin_unlock(&k->k_lock);
+}
+EXPORT_SYMBOL_GPL(klist_add_after);
+
+/**
+ * klist_add_before - Init a klist_node and add it before an existing node
+ * @n: node we're adding.
+ * @pos: node to put @n after
+ */
+void klist_add_before(struct klist_node *n, struct klist_node *pos)
{
+ struct klist *k = knode_klist(pos);
+
klist_node_init(k, n);
- add_tail(k, n);
+ spin_lock(&k->k_lock);
+ list_add_tail(&n->n_node, &pos->n_node);
+ spin_unlock(&k->k_lock);
}
+EXPORT_SYMBOL_GPL(klist_add_before);
-EXPORT_SYMBOL_GPL(klist_add_tail);
+struct klist_waiter {
+ struct list_head list;
+ struct klist_node *node;
+ struct task_struct *process;
+ int woken;
+};
+static DEFINE_SPINLOCK(klist_remove_lock);
+static LIST_HEAD(klist_remove_waiters);
-static void klist_release(struct kref * kref)
+static void klist_release(struct kref *kref)
{
- struct klist_node * n = container_of(kref, struct klist_node, n_ref);
+ struct klist_waiter *waiter, *tmp;
+ struct klist_node *n = container_of(kref, struct klist_node, n_ref);
+
+ WARN_ON(!knode_dead(n));
list_del(&n->n_node);
- complete(&n->n_removed);
- n->n_klist = NULL;
+ spin_lock(&klist_remove_lock);
+ list_for_each_entry_safe(waiter, tmp, &klist_remove_waiters, list) {
+ if (waiter->node != n)
+ continue;
+
+ waiter->woken = 1;
+ mb();
+ wake_up_process(waiter->process);
+ list_del(&waiter->list);
+ }
+ spin_unlock(&klist_remove_lock);
+ knode_set_klist(n, NULL);
}
-static int klist_dec_and_del(struct klist_node * n)
+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)
+static void klist_put(struct klist_node *n, bool kill)
{
- struct klist * k = n->n_klist;
+ struct klist *k = knode_klist(n);
+ void (*put)(struct klist_node *) = k->put;
spin_lock(&k->k_lock);
- klist_dec_and_del(n);
+ if (kill)
+ knode_kill(n);
+ if (!klist_dec_and_del(n))
+ put = NULL;
spin_unlock(&k->k_lock);
+ if (put)
+ put(n);
}
+/**
+ * klist_del - Decrement the reference count of node and try to remove.
+ * @n: node we're deleting.
+ */
+void klist_del(struct klist_node *n)
+{
+ klist_put(n, true);
+}
EXPORT_SYMBOL_GPL(klist_del);
-
/**
- * klist_remove - Decrement the refcount of node and wait for it to go away.
- * @n: node we're removing.
+ * 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)
+void klist_remove(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);
- wait_for_completion(&n->n_removed);
+ struct klist_waiter waiter;
+
+ waiter.node = n;
+ waiter.process = current;
+ waiter.woken = 0;
+ spin_lock(&klist_remove_lock);
+ list_add(&waiter.list, &klist_remove_waiters);
+ spin_unlock(&klist_remove_lock);
+
+ klist_del(n);
+
+ for (;;) {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ if (waiter.woken)
+ break;
+ schedule();
+ }
+ __set_current_state(TASK_RUNNING);
}
-
EXPORT_SYMBOL_GPL(klist_remove);
-
/**
- * klist_node_attached - Say whether a node is bound to a list or not.
- * @n: Node that we're testing.
+ * klist_node_attached - Say whether a node is bound to a list or not.
+ * @n: Node that we're testing.
*/
-
-int klist_node_attached(struct klist_node * n)
+int klist_node_attached(struct klist_node *n)
{
return (n->n_klist != NULL);
}
-
EXPORT_SYMBOL_GPL(klist_node_attached);
-
/**
- * 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.
+ * 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.
+ * 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)
+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;
+ if (n)
+ kref_get(&n->n_ref);
}
-
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.
+ * 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.
+ * Similar to klist_iter_init_node(), but start with the list head.
*/
-
-void klist_iter_init(struct klist * k, struct klist_iter * i)
+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.
+ * 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.
+ * 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)
+void klist_iter_exit(struct klist_iter *i)
{
if (i->i_cur) {
- klist_del(i->i_cur);
+ klist_put(i->i_cur, false);
i->i_cur = NULL;
}
}
-
EXPORT_SYMBOL_GPL(klist_iter_exit);
-
-static struct klist_node * to_klist_node(struct list_head * n)
+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.
+ * 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.
+ * 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 klist_node *klist_next(struct klist_iter *i)
{
- struct list_head * next;
- struct klist_node * knode = NULL;
+ void (*put)(struct klist_node *) = i->i_klist->put;
+ struct klist_node *last = i->i_cur;
+ struct klist_node *next;
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);
+ if (last) {
+ next = to_klist_node(last->n_node.next);
+ if (!klist_dec_and_del(last))
+ put = NULL;
+ } else
+ next = to_klist_node(i->i_klist->k_list.next);
+
+ i->i_cur = NULL;
+ while (next != to_klist_node(&i->i_klist->k_list)) {
+ if (likely(!knode_dead(next))) {
+ kref_get(&next->n_ref);
+ i->i_cur = next;
+ break;
+ }
+ next = to_klist_node(next->n_node.next);
}
- i->i_cur = knode;
+
spin_unlock(&i->i_klist->k_lock);
- return knode;
-}
+ if (put && last)
+ put(last);
+ return i->i_cur;
+}
EXPORT_SYMBOL_GPL(klist_next);
-
-
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff