--- /dev/null
+/*
+ * Descending-priority-sorted double-linked list
+ *
+ * (C) 2002-2003 Intel Corp
+ * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
+ *
+ * 2001-2005 (c) MontaVista Software, Inc.
+ * Daniel Walker <dwalker@mvista.com>
+ *
+ * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
+ *
+ * Simplifications of the original code by
+ * Oleg Nesterov <oleg@tv-sign.ru>
+ *
+ * Licensed under the FSF's GNU Public License v2 or later.
+ *
+ * Based on simple lists (include/linux/list.h).
+ *
+ * This is a priority-sorted list of nodes; each node has a
+ * priority from INT_MIN (highest) to INT_MAX (lowest).
+ *
+ * Addition is O(K), removal is O(1), change of priority of a node is
+ * O(K) and K is the number of RT priority levels used in the system.
+ * (1 <= K <= 99)
+ *
+ * This list is really a list of lists:
+ *
+ * - The tier 1 list is the prio_list, different priority nodes.
+ *
+ * - The tier 2 list is the node_list, serialized nodes.
+ *
+ * Simple ASCII art explanation:
+ *
+ * |HEAD |
+ * | |
+ * |prio_list.prev|<------------------------------------|
+ * |prio_list.next|<->|pl|<->|pl|<--------------->|pl|<-|
+ * |10 | |10| |21| |21| |21| |40| (prio)
+ * | | | | | | | | | | | |
+ * | | | | | | | | | | | |
+ * |node_list.next|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
+ * |node_list.prev|<------------------------------------|
+ *
+ * The nodes on the prio_list list are sorted by priority to simplify
+ * the insertion of new nodes. There are no nodes with duplicate
+ * priorites on the list.
+ *
+ * The nodes on the node_list is ordered by priority and can contain
+ * entries which have the same priority. Those entries are ordered
+ * FIFO
+ *
+ * Addition means: look for the prio_list node in the prio_list
+ * for the priority of the node and insert it before the node_list
+ * entry of the next prio_list node. If it is the first node of
+ * that priority, add it to the prio_list in the right position and
+ * insert it into the serialized node_list list
+ *
+ * Removal means remove it from the node_list and remove it from
+ * the prio_list if the node_list list_head is non empty. In case
+ * of removal from the prio_list it must be checked whether other
+ * entries of the same priority are on the list or not. If there
+ * is another entry of the same priority then this entry has to
+ * replace the removed entry on the prio_list. If the entry which
+ * is removed is the only entry of this priority then a simple
+ * remove from both list is sufficient.
+ *
+ * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
+ * is lowest priority.
+ *
+ * No locking is done, up to the caller.
+ *
+ */
+#ifndef _LINUX_PLIST_H_
+#define _LINUX_PLIST_H_
+
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/spinlock_types.h>
+
+struct plist_head {
+ struct list_head prio_list;
+ struct list_head node_list;
+#ifdef CONFIG_DEBUG_PI_LIST
+ spinlock_t *lock;
+#endif
+};
+
+struct plist_node {
+ int prio;
+ struct plist_head plist;
+};
+
+#ifdef CONFIG_DEBUG_PI_LIST
+# define PLIST_HEAD_LOCK_INIT(_lock) .lock = _lock
+#else
+# define PLIST_HEAD_LOCK_INIT(_lock)
+#endif
+
+/**
+ * #PLIST_HEAD_INIT - static struct plist_head initializer
+ *
+ * @head: struct plist_head variable name
+ */
+#define PLIST_HEAD_INIT(head, _lock) \
+{ \
+ .prio_list = LIST_HEAD_INIT((head).prio_list), \
+ .node_list = LIST_HEAD_INIT((head).node_list), \
+ PLIST_HEAD_LOCK_INIT(&(_lock)) \
+}
+
+/**
+ * #PLIST_NODE_INIT - static struct plist_node initializer
+ *
+ * @node: struct plist_node variable name
+ * @__prio: initial node priority
+ */
+#define PLIST_NODE_INIT(node, __prio) \
+{ \
+ .prio = (__prio), \
+ .plist = PLIST_HEAD_INIT((node).plist, NULL), \
+}
+
+/**
+ * plist_head_init - dynamic struct plist_head initializer
+ *
+ * @head: &struct plist_head pointer
+ */
+static inline void
+plist_head_init(struct plist_head *head, spinlock_t *lock)
+{
+ INIT_LIST_HEAD(&head->prio_list);
+ INIT_LIST_HEAD(&head->node_list);
+#ifdef CONFIG_DEBUG_PI_LIST
+ head->lock = lock;
+#endif
+}
+
+/**
+ * plist_node_init - Dynamic struct plist_node initializer
+ *
+ * @node: &struct plist_node pointer
+ * @prio: initial node priority
+ */
+static inline void plist_node_init(struct plist_node *node, int prio)
+{
+ node->prio = prio;
+ plist_head_init(&node->plist, NULL);
+}
+
+extern void plist_add(struct plist_node *node, struct plist_head *head);
+extern void plist_del(struct plist_node *node, struct plist_head *head);
+
+/**
+ * plist_for_each - iterate over the plist
+ *
+ * @pos1: the type * to use as a loop counter.
+ * @head: the head for your list.
+ */
+#define plist_for_each(pos, head) \
+ list_for_each_entry(pos, &(head)->node_list, plist.node_list)
+
+/**
+ * plist_for_each_entry_safe - iterate over a plist of given type safe
+ * against removal of list entry
+ *
+ * @pos1: the type * to use as a loop counter.
+ * @n1: another type * to use as temporary storage
+ * @head: the head for your list.
+ */
+#define plist_for_each_safe(pos, n, head) \
+ list_for_each_entry_safe(pos, n, &(head)->node_list, plist.node_list)
+
+/**
+ * plist_for_each_entry - iterate over list of given type
+ *
+ * @pos: the type * to use as a loop counter.
+ * @head: the head for your list.
+ * @member: the name of the list_struct within the struct.
+ */
+#define plist_for_each_entry(pos, head, mem) \
+ list_for_each_entry(pos, &(head)->node_list, mem.plist.node_list)
+
+/**
+ * plist_for_each_entry_safe - iterate over list of given type safe against
+ * removal of list entry
+ *
+ * @pos: the type * to use as a loop counter.
+ * @n: another type * to use as temporary storage
+ * @head: the head for your list.
+ * @m: the name of the list_struct within the struct.
+ */
+#define plist_for_each_entry_safe(pos, n, head, m) \
+ list_for_each_entry_safe(pos, n, &(head)->node_list, m.plist.node_list)
+
+/**
+ * plist_head_empty - return !0 if a plist_head is empty
+ *
+ * @head: &struct plist_head pointer
+ */
+static inline int plist_head_empty(const struct plist_head *head)
+{
+ return list_empty(&head->node_list);
+}
+
+/**
+ * plist_node_empty - return !0 if plist_node is not on a list
+ *
+ * @node: &struct plist_node pointer
+ */
+static inline int plist_node_empty(const struct plist_node *node)
+{
+ return plist_head_empty(&node->plist);
+}
+
+/* All functions below assume the plist_head is not empty. */
+
+/**
+ * plist_first_entry - get the struct for the first entry
+ *
+ * @ptr: the &struct plist_head pointer.
+ * @type: the type of the struct this is embedded in.
+ * @member: the name of the list_struct within the struct.
+ */
+#ifdef CONFIG_DEBUG_PI_LIST
+# define plist_first_entry(head, type, member) \
+({ \
+ WARN_ON(plist_head_empty(head)); \
+ container_of(plist_first(head), type, member); \
+})
+#else
+# define plist_first_entry(head, type, member) \
+ container_of(plist_first(head), type, member)
+#endif
+
+/**
+ * plist_first - return the first node (and thus, highest priority)
+ *
+ * @head: the &struct plist_head pointer
+ *
+ * Assumes the plist is _not_ empty.
+ */
+static inline struct plist_node* plist_first(const struct plist_head *head)
+{
+ return list_entry(head->node_list.next,
+ struct plist_node, plist.node_list);
+}
+
+#endif
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