On Mon, Mar 9, 2015 at 3:32 AM, Xunlei Pang <xlp...@126.com> wrote:
> From: Xunlei Pang <pang.xun...@linaro.org>
>
> If there're multiple nodes with the same prio as @node, currently
> plist_add() will add @node behind all of them. Now we need to add
> @node before all of these nodes for SMP RT scheduler.
>
> This patch adds a common __plist_add() for adding @node before or
> after existing nodes with the same prio, then adds plist_add_head()
> and plist_add_tail() inline wrapper functions for convenient uses.
>
> Finally, define plist_add() as plist_add_tail() which has the same
> behaviour as before.
>
> cc: Andrew Morton <a...@linux-foundation.org>
> cc: Dan Streetman <ddstr...@ieee.org>
> Signed-off-by: Xunlei Pang <pang.xun...@linaro.org>
> ---
> include/linux/plist.h | 30 +++++++++++++++++++++++++++++-
> lib/plist.c | 24 +++++++++++++++++++++---
> 2 files changed, 50 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/plist.h b/include/linux/plist.h
> index 9788360..10c834c 100644
> --- a/include/linux/plist.h
> +++ b/include/linux/plist.h
> @@ -138,7 +138,35 @@ static inline void plist_node_init(struct plist_node
> *node, int prio)
> INIT_LIST_HEAD(&node->node_list);
> }
>
> -extern void plist_add(struct plist_node *node, struct plist_head *head);
> +extern void __plist_add(struct plist_node *node,
> + struct plist_head *head, bool is_head);
> +
> +/**
> + * plist_add_head - add @node to @head, before all existing same-prio nodes
> + *
> + * @node: &struct plist_node pointer
> + * @head: &struct plist_head pointer
> + */
> +static inline
> +void plist_add_head(struct plist_node *node, struct plist_head *head)
> +{
> + __plist_add(node, head, true);
> +}
> +
> +/**
> + * plist_add_tail - add @node to @head, after all existing same-prio nodes
> + *
> + * @node: &struct plist_node pointer
> + * @head: &struct plist_head pointer
> + */
> +static inline
> +void plist_add_tail(struct plist_node *node, struct plist_head *head)
> +{
> + __plist_add(node, head, false);
> +}
> +
> +#define plist_add plist_add_tail
> +
> extern void plist_del(struct plist_node *node, struct plist_head *head);
>
> extern void plist_requeue(struct plist_node *node, struct plist_head *head);
> diff --git a/lib/plist.c b/lib/plist.c
> index 3a30c53..d3ebac6 100644
> --- a/lib/plist.c
> +++ b/lib/plist.c
> @@ -66,12 +66,16 @@ static void plist_check_head(struct plist_head *head)
> #endif
>
> /**
> - * plist_add - add @node to @head
> + * __plist_add - add @node to @head
> *
> * @node: &struct plist_node pointer
> * @head: &struct plist_head pointer
> + * @is_head: bool
> + *
> + * If there're any nodes with the same prio, add @node
> + * behind or before all of them according to @is_head.
> */
> -void plist_add(struct plist_node *node, struct plist_head *head)
> +void __plist_add(struct plist_node *node, struct plist_head *head, bool
> is_head)
> {
> struct plist_node *first, *iter, *prev = NULL;
> struct list_head *node_next = &head->node_list;
> @@ -96,8 +100,22 @@ void plist_add(struct plist_node *node, struct plist_head
> *head)
> struct plist_node, prio_list);
> } while (iter != first);
>
> - if (!prev || prev->prio != node->prio)
> + if (!prev || prev->prio != node->prio) {
> list_add_tail(&node->prio_list, &iter->prio_list);
> + } else if (is_head) {
> + /*
> + * prev has the same priority as the node that is
> + * being added. It is also the first node for this
> + * priority, but the new node needs to be added ahead of
> + * it. To accomplish this, insert node right after prev
> + * in the prio_list and then remove prev from that list.
> + * Then set node_next to prev->node_list so that the
> + * new node gets added before prev and not iter.
> + */
> + list_add(&node->prio_list, &prev->prio_list);
> + list_del_init(&prev->prio_list);
I think this can just be
list_replace_init(&prev->prio_list, &node->prio_list);
besides that,
Reviewed-by: Dan Streetman <ddstr...@ieee.org>
> + node_next = &prev->node_list;
> + }
> ins_node:
> list_add_tail(&node->node_list, node_next);
>
> --
> 1.9.1
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
