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plist: Add plist_last 

plist is currently used by the scheduler, which only needs to know the
highest item in the list.  This adds plist_last which allows you to
find the lowest.  This is necessary for using plists to implement a
fast search of dynamic ranges in pm_qos which can have both highest
and lowest criteria.

Signed-off-by: James Bottomley <James.Bottomley@suse.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
This commit is contained in:
James Bottomley 2010-07-01 21:46:36 +02:00 committed by Rafael J. Wysocki
parent c125e96f04
commit 12e4d0cc2e
1 changed files with 29 additions and 0 deletions
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29
include/linux/plist.h
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@ -259,6 +259,23 @@ static inline int plist_node_empty(const struct plist_node *node)
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_struct within the struct
*/
#ifdef CONFIG_DEBUG_PI_LIST
# 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_first - return the first node (and thus, highest priority)
* @head: the &struct plist_head pointer
@ -271,4 +288,16 @@ static inline struct plist_node *plist_first(const struct plist_head *head)
struct plist_node, plist.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, plist.node_list);
}
#endif