list.h: Add list_splice_tail() and list_splice_tail_init()

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().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/dma/ioat_dma.c b/drivers/dma/ioat_dma.c
index a52156e568867e827c30f0008de9477df493b730..bc8c6e3470ca258f6646c0ad2cd9278425296ec2 100644 (file)
--- a/drivers/dma/ioat_dma.c
+++ b/drivers/dma/ioat_dma.c
@@ -551,7 +551,7 @@ 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 2622b6596d7cc6283f6e0b34f2513826a25b0105..3712b925b3154b0eb8b19cd85cc01d4ad5ebceea 100644 (file)
--- 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 453916bc0412cbacd4ed2844fe71599ac07bc086..a886f27a11817c3303826d1f13ce5cf0255a38e7 100644 (file)
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -215,21 +215,21 @@ 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;
 }
 
 /**
- * list_splice - join two lists
+ * list_splice - join two lists, this is designed for stacks
  * @list: the new list to add.
  * @head: the place to add it in the first list.
  */
@@ -237,7 +237,19 @@ 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);
+}
+
+/**
+ * list_splice_tail - join two lists, each list being a queue
+ * @list: the new list to add.
+ * @head: the place to add it in the first list.
+ */
+static inline void list_splice_tail(struct list_head *list,
+                               struct list_head *head)
+{
+       if (!list_empty(list))
+               __list_splice(list, head->prev, head);
 }
 
 /**
@@ -251,7 +263,24 @@ 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);
+       }
+}
+
+/**
+ * list_splice_tail_init - join two lists, each list being a queue, and
+ *     reinitialise the emptied list.
+ * @list: the new list to add.
+ * @head: the place to add it in the first list.
+ *
+ * The list at @list is reinitialised
+ */
+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);
        }
 }