--- x/fs/userfaultfd.c
+++ u/fs/userfaultfd.c
@@ -1641,6 +1641,7 @@ static int userfaultfd_unregister(struct
 			ret = split_vma(mm, vma, end, 0);
 			if (ret)
 				break;
+			mas_pause(&mas);
 		}
 	next:
 		/*