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