[PATCH v4 19/30] locking/lockdep: Add helper functions to operate on the searched path

[Yuyang Du]

 - find_lock_in_path() tries to find whether a lock class is in the path.

 - find_next_dep_in_path() returns the next dependency after a
   given dependency in the path.

Signed-off-by: Yuyang Du <duyuyang@xxxxxxxxx>
---
 kernel/locking/lockdep.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 18303ff..41cb735 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1535,6 +1535,37 @@ static inline int get_lock_depth(struct lock_list *child)
 }
 
 /*
+ * Return the dependency if @lock is in the path, otherwise NULL.
+ */
+static inline struct lock_list *
+find_lock_in_path(struct lock_class *lock, struct lock_list *target)
+{
+	while ((target = get_lock_parent(target)))
+		if (fw_dep_class(target) == lock)
+			return target;
+
+	return NULL;
+}
+
+/*
+ * Walk back to the next dependency after @source from @target. Note
+ * that @source must be in the path, and @source can not be the same as
+ * @target, otherwise this is going to fail and reutrn NULL.
+ */
+static inline struct lock_list *
+find_next_dep_in_path(struct lock_list *source, struct lock_list *target)
+{
+	while (get_lock_parent(target) != source) {
+		target = get_lock_parent(target);
+
+		if (!target)
+			break;
+	}
+
+	return target;
+}
+
+/*
  * Return the forward or backward dependency list.
  *
  * @lock:    the lock_list to get its class's dependency list
-- 
1.8.3.1