Emacs freeze with async command

Question

Emacs 27.0.50. Windows 10.

This function works finely when the line is commented:

(defun Pfedj/write-async-file ()
  (interactive)
  (async-start (lambda ()
                 (setq path "~/org/file.org")
                 (find-file path)
                 (dotimes (i 500)
                   (beginning-of-buffer)
                   ;;(kill-whole-line) ;; <= with this line Emacs freezes for 20-30 sec
                   (insert "foobar \n")
                   (save-buffer))
                 222)
               (lambda (result)
                 (message "Async process done, result should be 222: %s"
                          result))))

If the following steps will be executed: 1. M-x Pfedj/write-async-file 2. uncomment ;;(kill-whole-line) and repeat M-x Pfedj/write-async-file Emacs freezes for 20-30 sec.

Why does it happen? How can I profix it?

Answer 1

I could fix it by creating a new function in the file test.el that doesn't use kill ring.

test.el

(defun Pfedj/delete-line (&optional arg)
  (interactive "P")
  (flet ((kill-region (begin end)
                      (delete-region begin end)))
    (kill-line arg)))

(defun Pfedj/write-async-file ()
  (interactive)
  (async-start (lambda ()
                 (setq path "~/org/file.org")
                 (find-file path)
                 (load-file "~/.emacs.d/test.el")
                 (dotimes (i 400)
                   (beginning-of-buffer)
                   ;(kill-whole-line)
                   (Pfedj/delete-line)
                   (insert "foobar \n")
                   (save-buffer))
                 222)
               (lambda (result)
                 (message "Async process done, result should be 222: %s"
                          result))))

Now it works if smb can give explanation why it is so I welcome it.