Merge back earlier ACPI PM material for v4.3.

1 files changed, 41 insertions, 0 deletions

diff --git a/lib/klist.c b/lib/klist.c
index 89b485a2a58d..d74cf7a29afd 100644
--- a/lib/klist.c
+++ b/lib/klist.c
@@ -324,6 +324,47 @@ static struct klist_node *to_klist_node(struct list_head *n)
 }
 
 /**
+ * klist_prev - Ante up prev node in list.
+ * @i: Iterator structure.
+ *
+ * First grab list lock. Decrement the reference count of the previous
+ * node, if there was one. Grab the prev node, increment its reference
+ * count, drop the lock, and return that prev node.
+ */
+struct klist_node *klist_prev(struct klist_iter *i)
+{
+        void (*put)(struct klist_node *) = i->i_klist->put;
+        struct klist_node *last = i->i_cur;
+        struct klist_node *prev;
+
+        spin_lock(&i->i_klist->k_lock);
+
+        if (last) {
+                prev = to_klist_node(last->n_node.prev);
+                if (!klist_dec_and_del(last))
+                        put = NULL;
+        } else
+                prev = to_klist_node(i->i_klist->k_list.prev);
+
+        i->i_cur = NULL;
+        while (prev != to_klist_node(&i->i_klist->k_list)) {
+                if (likely(!knode_dead(prev))) {
+                        kref_get(&prev->n_ref);
+                        i->i_cur = prev;
+                        break;
+                }
+                prev = to_klist_node(prev->n_node.prev);
+        }
+
+        spin_unlock(&i->i_klist->k_lock);
+
+        if (put && last)
+                put(last);
+        return i->i_cur;
+}
+EXPORT_SYMBOL_GPL(klist_prev);
+
+/**
  * klist_next - Ante up next node in list.
  * @i: Iterator structure.
  *