diff --git a/core/state/snapshot/snapshot.go b/core/state/snapshot/snapshot.go
index 6cc8f3831c..d1ffb5cc2d 100644
--- a/core/state/snapshot/snapshot.go
+++ b/core/state/snapshot/snapshot.go
@@ -258,6 +258,8 @@ func (t *Tree) Disable() {
 	for _, layer := range t.layers {
 		switch layer := layer.(type) {
 		case *diskLayer:
+			// TODO this function will hang if it's called twice. Will
+			// fix it in the following PRs.
 			layer.stopGeneration()
 			layer.markStale()
 			layer.Release()
@@ -715,6 +717,8 @@ func (t *Tree) Rebuild(root common.Hash) {
 	for _, layer := range t.layers {
 		switch layer := layer.(type) {
 		case *diskLayer:
+			// TODO this function will hang if it's called twice. Will
+			// fix it in the following PRs.
 			layer.stopGeneration()
 			layer.markStale()
 			layer.Release()