diff options
Diffstat (limited to 'net/rds/xlist.h')
-rw-r--r-- | net/rds/xlist.h | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/net/rds/xlist.h b/net/rds/xlist.h new file mode 100644 index 00000000000..8c21aca49d5 --- /dev/null +++ b/net/rds/xlist.h @@ -0,0 +1,110 @@ +#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 |