bug#46022: 27.1; kill-emacs should call sd_notify only in daemon mode

[Eli Zaretskii]

> Cc: 46022@debbugs.gnu.org
> From: Lucas Werkmeister <mail@lucaswerkmeister.de>
> Date: Thu, 21 Jan 2021 21:12:03 +0100
> 
> Hm, I wasn’t aware systemd logged those warnings. Probably a good idea
> to guard the sd_notify(0, "STOPPING=1") with a guard on (a stashed copy
> of?) daemon_type, then, yes.

OK, thanks.  Does the patch below seems reasonable and give good
results?  If yes, I'd like it to go into the upcoming Emacs 27.2.

diff --git a/src/emacs.c b/src/emacs.c
index f2e858f..67220eb 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -187,7 +187,8 @@ #define MAIN_PROGRAM
 /* Name for the server started by the daemon.*/
 static char *daemon_name;
 
-/* 0 not a daemon, 1 new-style (foreground), 2 old-style (background).  */
+/* 0 not a daemon, 1 new-style (foreground), 2 old-style (background).
+   A negative value means the daemon initialization was already done.  */
 int daemon_type;
 
 #ifndef WINDOWSNT
@@ -2371,7 +2372,10 @@ DEFUN ("kill-emacs", Fkill_emacs, Skill_emacs, 0, 1, "P",
   int exit_code;
 
 #ifdef HAVE_LIBSYSTEMD
-  sd_notify(0, "STOPPING=1");
+  /* Notify systemd we are shutting down, but only if we have notified
+     it about startup.  */
+  if (daemon_type == -1)
+    sd_notify(0, "STOPPING=1");
 #endif /* HAVE_LIBSYSTEMD */
 
   /* Fsignal calls emacs_abort () if it sees that waiting_for_input is
@@ -2876,7 +2880,7 @@ DEFUN ("daemon-initialized", Fdaemon_initialized, 
Sdaemon_initialized, 0, 0, 0,
     }
 
   /* Set it to an invalid value so we know we've already run this function.  */
-  daemon_type = -1;
+  daemon_type = -daemon_type;
 
 #else  /* WINDOWSNT */
   /* Signal the waiting emacsclient process.  */