Oleg Nesterov wrote:
>
> Daniel Walker wrote:
> >
> > Description:
> > This patch adds the priority list data structure from Inaky Perez-Gonzalez
> > to the Preempt Real-Time mutex.
> >
> ...
>
> I can't understand how this can work.
And I think it is possible to simplify plist's design.
struct plist {
int prio;
struct list_head prio_list;
struct list_head node_list;
};
#define plist_for_each(pos, head) \
list_for_each_entry(pos, &(head)->node_list, node_list)
static inline void plist_add(struct plist *new, struct plist *head)
{
struct plist* pos;
INIT_LIST_HEAD(&new->prio_list);
list_for_each_entry(pos, &head->prio_list, prio_list)
if (new->prio < pos->prio)
goto lt_prio;
else if (new->prio == pos->prio) {
pos = list_entry(pos->prio_list.next,
struct plist, prio_list);
goto eq_prio;
}
lt_prio:
list_add_tail(&new->prio_list, &pos->prio_list);
eq_prio:
list_add_tail(&new->node_list, &pos->node_list);
}
static inline void plist_del(struct plist *del)
{
if (!list_empty(&del->prio_list)) {
struct plist *next = list_entry(del->node_list.next,
struct plist, node_list);
list_move_tail(&next->prio_list, &del->prio_list);
list_del_init(&del->prio_list);
}
list_del_init(&del->node_list);
}
All nodes in prio list are chained via ->node_list, sorted in ascending
->prio/fifo order. Nodes which start different priority slice are chained
via ->prio_list, ascending ->prio order.
Slightly tested, seems to work.
I think this would be even better:
struct plist_head {
struct list_head prio_list;
struct list_head node_list;
}
struct plist {
int prio;
struct plist_head head;
}
The plist_head's min/max prio can be found from
plist_head.prio_list.next/prev.
What do you think?
Oleg.
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