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Subject[RFC/PATCH 2/5] rt: list_splice2
Introduce list_splice2{,_tail}() which will splice a sub-list denoted
by two list items instead of the full list.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
drivers/usb/host/ehci-q.c | 2 -
include/linux/list.h | 66 ++++++++++++++++++++++++++++++++++++++++------
lib/lock_list.c | 2 -
3 files changed, 60 insertions(+), 10 deletions(-)

Index: linux-2.6/include/linux/list.h
===================================================================
--- linux-2.6.orig/include/linux/list.h
+++ linux-2.6/include/linux/list.h
@@ -320,17 +320,17 @@ static inline int list_empty_careful(con
}

static inline void __list_splice(struct list_head *list,
- struct list_head *head)
+ struct list_head *prev,
+ struct list_head *next)
{
struct list_head *first = list->next;
struct list_head *last = list->prev;
- struct list_head *at = head->next;

- first->prev = head;
- head->next = first;
+ first->prev = prev;
+ prev->next = first;

- last->next = at;
- at->prev = last;
+ last->next = next;
+ next->prev = last;
}

/**
@@ -341,7 +341,13 @@ static inline void __list_splice(struct
static inline void list_splice(struct list_head *list, struct list_head *head)
{
if (!list_empty(list))
- __list_splice(list, head);
+ __list_splice(list, head, head->next);
+}
+
+static inline void list_splice_tail(struct list_head *list, struct list_head *head)
+{
+ if (!list_empty(list))
+ __list_splice(list, head->prev, head);
}

/**
@@ -355,11 +361,55 @@ static inline void list_splice_init(stru
struct list_head *head)
{
if (!list_empty(list)) {
- __list_splice(list, head);
+ __list_splice(list, head, head->next);
+ INIT_LIST_HEAD(list);
+ }
+}
+
+static inline void list_splice_tail_init(struct list_head *list,
+ struct list_head *head)
+{
+ if (!list_empty(list)) {
+ __list_splice(list, head->prev, head);
INIT_LIST_HEAD(list);
}
}

+static inline void __list_splice2(struct list_head *first,
+ struct list_head *last,
+ struct list_head *prev,
+ struct list_head *next)
+{
+ first->prev->next = last->next;
+ last->next->prev = first->prev;
+
+ first->prev = prev;
+ prev->next = first;
+
+ last->next = next;
+ next->prev = last;
+}
+
+/**
+ * list_splice2 - join [first, last] to head
+ * @first: list item
+ * @last: list item further on the same list
+ * @head: the place to add it on another list
+ */
+static inline void list_splice2(struct list_head *first,
+ struct list_head *last,
+ struct list_head *head)
+{
+ __list_splice2(first, last, head, head->next);
+}
+
+static inline void list_splice2_tail(struct list_head *first,
+ struct list_head *last,
+ struct list_head *head)
+{
+ __list_splice2(first, last, head->prev, head);
+}
+
/**
* list_splice_init_rcu - splice an RCU-protected list into an existing list.
* @list: the RCU-protected list to splice
Index: linux-2.6/drivers/usb/host/ehci-q.c
===================================================================
--- linux-2.6.orig/drivers/usb/host/ehci-q.c
+++ linux-2.6/drivers/usb/host/ehci-q.c
@@ -887,7 +887,7 @@ static struct ehci_qh *qh_append_tds (

list_del (&qtd->qtd_list);
list_add (&dummy->qtd_list, qtd_list);
- __list_splice (qtd_list, qh->qtd_list.prev);
+ list_splice_tail (qtd_list, &qh->qtd_list);

ehci_qtd_init(ehci, qtd, qtd->qtd_dma);
qh->dummy = qtd;
Index: linux-2.6/lib/lock_list.c
===================================================================
--- linux-2.6.orig/lib/lock_list.c
+++ linux-2.6/lib/lock_list.c
@@ -128,7 +128,7 @@ void lock_list_splice_init(struct lock_l
lock = __lock_list_reverse(list);
if (!list_empty(&list->head)) {
spin_lock_nested(&head->lock, LOCK_LIST_NESTING_NEXT);
- __list_splice(&list->head, &head->head);
+ __list_splice(&list->head, &head->head, head->head.next);
INIT_LIST_HEAD(&list->head);
spin_unlock(&head->lock);
}
--

-
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