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 /* SPDX-License-Identifier: GPL-2.0-or-later */
 /*
  * 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>
  *
  * 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:
  *
  * pl:prio_list (only for plist_node)
  * nl:node_list
  *   HEAD|             NODE(S)
  *       |
  *       ||------------------------------------|
  *       ||->|pl|<->|pl|<--------------->|pl|<-|
  *       |   |10|   |21|   |21|   |21|   |40|   (prio)
  *       |   |  |   |  |   |  |   |  |   |  |
  *       |   |  |   |  |   |  |   |  |   |  |
  * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
  * |-------------------------------------------|
  *
  * 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 are 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/container_of.h>
 #include <linux/list.h>
 #include <linux/types.h>
 
 #include <asm/bug.h>
 
 struct plist_head {
     struct list_head node_list;
 };
 
 struct plist_node {
     int         prio;
     struct list_head    prio_list;
     struct list_head    node_list;
 };
 
 /**
  * PLIST_HEAD_INIT - static struct plist_head initializer
  * @head:   struct plist_head variable name
  */
 #define PLIST_HEAD_INIT(head)               \
 {                           \
     .node_list = LIST_HEAD_INIT((head).node_list)   \
 }
 
 /**
  * PLIST_HEAD - declare and init plist_head
  * @head:   name for struct plist_head variable
  */
 #define PLIST_HEAD(head) \
     struct plist_head head = PLIST_HEAD_INIT(head)
 
 /**
  * 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),              \
     .prio_list = LIST_HEAD_INIT((node).prio_list),  \
     .node_list = LIST_HEAD_INIT((node).node_list),  \
 }
 
 /**
  * plist_head_init - dynamic struct plist_head initializer
  * @head:   &struct plist_head pointer
  */
 static inline void
 plist_head_init(struct plist_head *head)
 {
     INIT_LIST_HEAD(&head->node_list);
 }
 
 /**
  * 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;
     INIT_LIST_HEAD(&node->prio_list);
     INIT_LIST_HEAD(&node->node_list);
 }
 
 extern void plist_add(struct plist_node *node, struct plist_head *head);
 extern void plist_del(struct plist_node *node, struct plist_head *head);
 
 extern void plist_requeue(struct plist_node *node, struct plist_head *head);
 
 /**
  * plist_for_each - iterate over the plist
  * @pos:    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, node_list)
 
 /**
  * plist_for_each_continue - continue iteration over the plist
  * @pos:    the type * to use as a loop cursor
  * @head:   the head for your list
  *
  * Continue to iterate over plist, continuing after the current position.
  */
 #define plist_for_each_continue(pos, head)  \
      list_for_each_entry_continue(pos, &(head)->node_list, node_list)
 
 /**
  * plist_for_each_safe - iterate safely over a plist of given type
  * @pos:    the type * to use as a loop counter
  * @n:  another type * to use as temporary storage
  * @head:   the head for your list
  *
  * Iterate over a plist of given type, safe against removal of list entry.
  */
 #define plist_for_each_safe(pos, n, head)   \
      list_for_each_entry_safe(pos, n, &(head)->node_list, 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
  * @mem:    the name of the list_head within the struct
  */
 #define plist_for_each_entry(pos, head, mem)    \
      list_for_each_entry(pos, &(head)->node_list, mem.node_list)
 
 /**
  * plist_for_each_entry_continue - continue iteration over list of given type
  * @pos:    the type * to use as a loop cursor
  * @head:   the head for your list
  * @m:      the name of the list_head within the struct
  *
  * Continue to iterate over list of given type, continuing after
  * the current position.
  */
 #define plist_for_each_entry_continue(pos, head, m) \
     list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
 
 /**
  * plist_for_each_entry_safe - iterate safely over list of given type
  * @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_head within the struct
  *
  * Iterate over list of given type, safe against removal of list entry.
  */
 #define plist_for_each_entry_safe(pos, n, head, m)  \
     list_for_each_entry_safe(pos, n, &(head)->node_list, m.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 list_empty(&node->node_list);
 }
 
 /* All functions below assume the plist_head is not empty. */
 
 /**
  * plist_first_entry - get the struct for the first entry
  * @head:   the &struct plist_head pointer
  * @type:   the type of the struct this is embedded in
  * @member: the name of the list_head within the struct
  */
 #ifdef CONFIG_DEBUG_PLIST
 # 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_last_entry - get the struct for the last entry
  * @head:   the &struct plist_head pointer
  * @type:   the type of the struct this is embedded in
  * @member: the name of the list_head within the struct
  */
 #ifdef CONFIG_DEBUG_PLIST
 # define plist_last_entry(head, type, member)   \
 ({ \
     WARN_ON(plist_head_empty(head)); \
     container_of(plist_last(head), type, member); \
 })
 #else
 # define plist_last_entry(head, type, member)   \
     container_of(plist_last(head), type, member)
 #endif
 
 /**
  * plist_next - get the next entry in list
  * @pos:    the type * to cursor
  */
 #define plist_next(pos) \
     list_next_entry(pos, node_list)
 
 /**
  * plist_prev - get the prev entry in list
  * @pos:    the type * to cursor
  */
 #define plist_prev(pos) \
     list_prev_entry(pos, node_list)
 
 /**
  * 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, node_list);
 }
 
 /**
  * plist_last - return the last node (and thus, lowest priority)
  * @head:   the &struct plist_head pointer
  *
  * Assumes the plist is _not_ empty.
  */
 static inline struct plist_node *plist_last(const struct plist_head *head)
 {
     return list_entry(head->node_list.prev,
               struct plist_node, node_list);
 }
 
 #endif

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