On Mon, 2008-08-04 at 15:48 -0700, Luis R. Rodriguez wrote:
> If you are using linked lists for queues list_splice() will not do what
> you would expect even if you use the elements passed reversed. We need
> to handle these differently. We add list_splice_tail() and
> list_splice_tail_init()
In the -rt tree we have this:
---
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@xxxxxxxxx>
diff --git a/drivers/dma/ioat_dma.c b/drivers/dma/ioat_dma.c
index 318e8a2..dace60c 100644
--- a/drivers/dma/ioat_dma.c
+++ b/drivers/dma/ioat_dma.c
@@ -283,7 +283,7 @@ static dma_cookie_t ioat1_tx_submit(struct dma_async_tx_descriptor *tx)
/* write address into NextDescriptor field of last desc in chain */
to_ioat_desc(ioat_chan->used_desc.prev)->hw->next =
first->async_tx.phys;
- __list_splice(&new_chain, ioat_chan->used_desc.prev);
+ list_splice_tail(&new_chain, &ioat_chan->used_desc);
ioat_chan->dmacount += desc_count;
ioat_chan->pending += desc_count;
diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index b85b541..3c541d8 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -932,7 +932,7 @@ 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;
diff --git a/include/linux/list.h b/include/linux/list.h
index 08cf4f6..468e001 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -327,17 +327,17 @@ static inline int list_is_singular(const struct list_head *head)
}
static inline void __list_splice(const 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;
}
/**
@@ -349,7 +349,13 @@ static inline void list_splice(const 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);
}
/**
@@ -363,11 +369,55 @@ static inline void list_splice_init(struct list_head *list,
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
diff --git a/lib/lock_list.c b/lib/lock_list.c
index d4bd571..586c01e 100644
--- a/lib/lock_list.c
+++ b/lib/lock_list.c
@@ -128,7 +128,7 @@ void lock_list_splice_init(struct lock_list_head *list,
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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