1 files changed, 126 insertions, 0 deletions

diff --git a/include/linux/llist.h b/include/linux/llist.h
new file mode 100644
index 000000000000..aa0c8b5b3cd0
--- /dev/null
+++ b/include/linux/llist.h
@@ -0,0 +1,126 @@
+#ifndef LLIST_H
+#define LLIST_H
+/*
+ * Lock-less NULL terminated single linked list
+ *
+ * If there are multiple producers and multiple consumers, llist_add
+ * can be used in producers and llist_del_all can be used in
+ * consumers.  They can work simultaneously without lock.  But
+ * llist_del_first can not be used here.  Because llist_del_first
+ * depends on list->first->next does not changed if list->first is not
+ * changed during its operation, but llist_del_first, llist_add,
+ * llist_add (or llist_del_all, llist_add, llist_add) sequence in
+ * another consumer may violate that.
+ *
+ * If there are multiple producers and one consumer, llist_add can be
+ * used in producers and llist_del_all or llist_del_first can be used
+ * in the consumer.
+ *
+ * This can be summarized as follow:
+ *
+ *           |   add    | del_first |  del_all
+ * add       |    -     |     -     |     -
+ * del_first |          |     L     |     L
+ * del_all   |          |           |     -
+ *
+ * Where "-" stands for no lock is needed, while "L" stands for lock
+ * is needed.
+ *
+ * The list entries deleted via llist_del_all can be traversed with
+ * traversing function such as llist_for_each etc.  But the list
+ * entries can not be traversed safely before deleted from the list.
+ * The order of deleted entries is from the newest to the oldest added
+ * one.  If you want to traverse from the oldest to the newest, you
+ * must reverse the order by yourself before traversing.
+ *
+ * The basic atomic operation of this list is cmpxchg on long.  On
+ * architectures that don't have NMI-safe cmpxchg implementation, the
+ * list can NOT be used in NMI handler.  So code uses the list in NMI
+ * handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
+ */
+
+struct llist_head {
+        struct llist_node *first;
+};
+
+struct llist_node {
+        struct llist_node *next;
+};
+
+#define LLIST_HEAD_INIT(name)   { NULL }
+#define LLIST_HEAD(name)        struct llist_head name = LLIST_HEAD_INIT(name)
+
+/**
+ * init_llist_head - initialize lock-less list head
+ * @head:       the head for your lock-less list
+ */
+static inline void init_llist_head(struct llist_head *list)
+{
+        list->first = NULL;
+}
+
+/**
+ * llist_entry - get the struct of this entry
+ * @ptr:        the &struct llist_node pointer.
+ * @type:       the type of the struct this is embedded in.
+ * @member:     the name of the llist_node within the struct.
+ */
+#define llist_entry(ptr, type, member)          \
+        container_of(ptr, type, member)
+
+/**
+ * llist_for_each - iterate over some deleted entries of a lock-less list
+ * @pos:        the &struct llist_node to use as a loop cursor
+ * @node:       the first entry of deleted list entries
+ *
+ * In general, some entries of the lock-less list can be traversed
+ * safely only after being deleted from list, so start with an entry
+ * instead of list head.
+ *
+ * If being used on entries deleted from lock-less list directly, the
+ * traverse order is from the newest to the oldest added entry.  If
+ * you want to traverse from the oldest to the newest, you must
+ * reverse the order by yourself before traversing.
+ */
+#define llist_for_each(pos, node)                       \
+        for ((pos) = (node); pos; (pos) = (pos)->next)
+
+/**
+ * llist_for_each_entry - iterate over some deleted entries of lock-less list of given type
+ * @pos:        the type * to use as a loop cursor.
+ * @node:       the fist entry of deleted list entries.
+ * @member:     the name of the llist_node with the struct.
+ *
+ * In general, some entries of the lock-less list can be traversed
+ * safely only after being removed from list, so start with an entry
+ * instead of list head.
+ *
+ * If being used on entries deleted from lock-less list directly, the
+ * traverse order is from the newest to the oldest added entry.  If
+ * you want to traverse from the oldest to the newest, you must
+ * reverse the order by yourself before traversing.
+ */
+#define llist_for_each_entry(pos, node, member)                         \
+        for ((pos) = llist_entry((node), typeof(*(pos)), member);       \
+             &(pos)->member != NULL;                                    \
+             (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member))
+
+/**
+ * llist_empty - tests whether a lock-less list is empty
+ * @head:       the list to test
+ *
+ * Not guaranteed to be accurate or up to date.  Just a quick way to
+ * test whether the list is empty without deleting something from the
+ * list.
+ */
+static inline int llist_empty(const struct llist_head *head)
+{
+        return ACCESS_ONCE(head->first) == NULL;
+}
+
+void llist_add(struct llist_node *new, struct llist_head *head);
+void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
+                     struct llist_head *head);
+struct llist_node *llist_del_first(struct llist_head *head);
+struct llist_node *llist_del_all(struct llist_head *head);
+#endif /* LLIST_H */