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#ifndef _LINUX_XLIST_H
#define _LINUX_XLIST_H
#include <linux/stddef.h>
#include <linux/poison.h>
#include <linux/prefetch.h>
#include <asm/system.h>
struct xlist_head {
struct xlist_head *next;
};
/*
* XLIST_PTR_TAIL can be used to prevent double insertion. See
* xlist_protect()
*/
#define XLIST_PTR_TAIL ((struct xlist_head *)0x1)
static inline void xlist_add(struct xlist_head *new, struct xlist_head *tail, struct xlist_head *head)
{
struct xlist_head *cur;
struct xlist_head *check;
while (1) {
cur = head->next;
tail->next = cur;
check = cmpxchg(&head->next, cur, new);
if (check == cur)
break;
}
}
/*
* To avoid duplicate insertion by two CPUs of the same xlist item
* you can call xlist_protect. It will stuff XLIST_PTR_TAIL
* into the entry->next pointer with xchg, and only return 1
* if there was a NULL there before.
*
* if xlist_protect returns zero, someone else is busy working
* on this entry. Getting a NULL into the entry in a race
* free manner is the caller's job.
*/
static inline int xlist_protect(struct xlist_head *entry)
{
struct xlist_head *val;
val = xchg(&entry->next, XLIST_PTR_TAIL);
if (val == NULL)
return 1;
return 0;
}
static inline struct xlist_head *xlist_del_head(struct xlist_head *head)
{
struct xlist_head *cur;
struct xlist_head *check;
struct xlist_head *next;
while (1) {
cur = head->next;
if (!cur)
goto out;
if (cur == XLIST_PTR_TAIL) {
cur = NULL;
goto out;
}
next = cur->next;
check = cmpxchg(&head->next, cur, next);
if (check == cur)
goto out;
}
out:
return cur;
}
static inline struct xlist_head *xlist_del_head_fast(struct xlist_head *head)
{
struct xlist_head *cur;
cur = head->next;
if (!cur || cur == XLIST_PTR_TAIL)
return NULL;
head->next = cur->next;
return cur;
}
static inline void xlist_splice(struct xlist_head *list,
struct xlist_head *head)
{
struct xlist_head *cur;
WARN_ON(head->next);
cur = xchg(&list->next, NULL);
head->next = cur;
}
static inline void INIT_XLIST_HEAD(struct xlist_head *list)
{
list->next = NULL;
}
static inline int xlist_empty(struct xlist_head *head)
{
return head->next == NULL || head->next == XLIST_PTR_TAIL;
}
#endif
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