bugfix: infinite loop in

Author: karim-agha

src/payload/ext/checkpoint.rs

@@ -286,8 +286,10 @@ impl<P: Platform> CheckpointExt<P> for Checkpoint<P> {
 	/// by `Checkpoint::new_at_block`.
 	fn building_since(&self) -> Instant {
 		let mut created_at = self.created_at();
-		while let Some(prev) = self.prev() {
+		let mut current = self.clone();
+		while let Some(prev) = current.prev() {
 			created_at = prev.created_at();
+			current = prev;
 		}
 		created_at
 	}

src/pipelines/exec/scope.rs

@@ -107,13 +107,13 @@ impl<P: Platform> RootScope<P> {
 	) {
 		let next = scope_of(next_step);
 		let prev = self.current.replace(next.clone());
-		let mut root = self.root.write();
 
 		if prev != next {
 			// Scope changed. We will need to leave all scopes from `prev`
 			// up to the common ancestor, then enter all scopes from the
 			// common ancestor to `next`.
 			let common = prev.common_ancestor(&next);
+			let mut root = self.root.write();
 
 			for s in prev.between(&common) {
 				root.get_mut(&s).expect("scope should exist").leave();