try out starting an instance of flock(1) early in kill-emacs-hook

1 files changed, 16 insertions, 0 deletions

diff --git a/.emacs.d/init.el b/.emacs.d/init.el
index dbe06590..02185e93 100644
--- a/.emacs.d/init.el
+++ b/.emacs.d/init.el
@@ -2342,6 +2342,22 @@ Called by '~/src/dotfiles/bin/emacsclient --spw/update-environment'."
     (funcall orig-fun)))
 (advice-add 'comint-stop-subjob :around #'spw/comint-stop-subjob)
 
+;; flock(1) starting daemons named the same as us so that instances of my
+;; emacsclient(1) wrapper wait on us completing our exit before trying to
+;; start us again.
+(defun spw/daemon-lock-self ()
+  (when (and (daemonp) (executable-find "flock") (executable-find "sleep"))
+    (let ((file
+	   (file-name-concat
+	    (or (getenv "XDG_RUNTIME_DIR") (format "/run/user/%d" (user-uid)))
+	    "spw_emacsclient"
+	    (cl-etypecase (daemonp) (string (daemonp)) (t "server")))))
+      (set-process-query-on-exit-flag
+       (start-process "spw_emacsclient" nil
+		      "flock" "-E" "0" "-n" file "sleep" "infinity")
+       nil))))
+(add-hook 'kill-emacs-hook #'spw/daemon-lock-self -99)
+
 ;; open a frame on a new workspace with only the relevant dired buffer open,
 ;; eval this form: (global-set-key "\C-cG" #'spw/grading-advance)
 ;; and then use C-c G to open the first item (will need C-c f t after just