1 files changed, 110 insertions, 0 deletions
diff --git a/net/rds/xlist.h b/net/rds/xlist.h
new file mode 100644
index 000000000000..8c21aca49d50
--- /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