From ee0e5d34a0ad5f52c547fdd7d270ab451eccab4a Mon Sep 17 00:00:00 2001
From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
Date: Thu, 9 Dec 2021 23:53:12 -0500
Subject: [PATCH 5/5] services: dbus: Add synchronization primitives to dbus,
 elogind.

This is an (unsuccessful) to fix https://issues.guix.gnu.org/52051.
---
 gnu/services/dbus.scm    | 28 ++++++++++++++++++++--------
 gnu/services/desktop.scm | 35 +++++++++++++++++++++++++++--------
 2 files changed, 47 insertions(+), 16 deletions(-)

diff --git a/gnu/services/dbus.scm b/gnu/services/dbus.scm
index da167f2e36..c285531663 100644
--- a/gnu/services/dbus.scm
+++ b/gnu/services/dbus.scm
@@ -194,14 +194,26 @@ (define dbus-shepherd-service
             (documentation "Run the D-Bus system daemon.")
             (provision '(dbus-system))
             (requirement '(user-processes syslogd))
-            (start #~(make-forkexec-constructor
-                      (list (string-append #$dbus "/bin/dbus-daemon")
-                            "--nofork" "--system" "--syslog-only")
-                      #$@(if verbose?
-                             '(#:environment-variables '("DBUS_VERBOSE=1")
-                               #:log-file "/var/log/dbus-daemon.log")
-                             '())
-                      #:pid-file "/var/run/dbus/pid"))
+            (modules `((gnu build dbus-service)
+                       ,@%default-modules))
+            (start
+             (with-imported-modules '((gnu build dbus-service))
+               #~(lambda args
+                   (define pid
+                     ((make-forkexec-constructor
+                       (list (string-append #$dbus "/bin/dbus-daemon")
+                             "--nofork" "--system" "--syslog-only")
+                       #$@(if verbose?
+                              ;; Since the verbose output goes to the console,
+                              ;; not syslog, add a log file to capture it.
+                              '(#:environment-variables '("DBUS_VERBOSE=1")
+                                #:log-file "/var/log/dbus-daemon.log")
+                              '())
+                       #:pid-file "/var/run/dbus/pid")))
+                   ;; Ensure the system bus is ready to service requests
+                   ;; before returning.
+                   (wait-for-bus-readiness)
+                   pid)))
             (stop #~(make-kill-destructor)))))))
 
 (define dbus-root-service-type
diff --git a/gnu/services/desktop.scm b/gnu/services/desktop.scm
index 612d548eea..3208cb7aac 100644
--- a/gnu/services/desktop.scm
+++ b/gnu/services/desktop.scm
@@ -3,7 +3,7 @@
 ;;; Copyright © 2015 Andy Wingo <wingo@igalia.com>
 ;;; Copyright © 2015 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2016 Sou Bunnbu <iyzsong@gmail.com>
-;;; Copyright © 2017, 2020 Maxim Cournoyer <maxim.cournoyer@gmail.com>
+;;; Copyright © 2017, 2020, 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;; Copyright © 2017 Nikita <nikita@n0.is>
 ;;; Copyright © 2018, 2020 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2018 Ricardo Wurmus <rekado@elephly.net>
@@ -724,13 +724,32 @@ (define (elogind-shepherd-service config)
   (list (shepherd-service
          (requirement '(dbus-system))
          (provision '(elogind))
-         (start #~(make-forkexec-constructor
-                   (list #$(file-append (elogind-package config)
-                                        "/libexec/elogind/elogind"))
-                   #:environment-variables
-                   (list (string-append "ELOGIND_CONF_FILE="
-                                        #$(elogind-configuration-file
-                                           config)))))
+         (modules `((gnu build dbus-service)
+                    ,@%default-modules))
+         (start
+          (with-imported-modules '((gnu build dbus-service))
+            #~(lambda args
+                (define pid
+                  ((make-forkexec-constructor
+                    (list #$(file-append strace "/bin/strace") "-f"
+                          "-o/elogind.log" "-s700"
+                          #$(file-append (elogind-package config)
+                                         "/libexec/elogind/elogind"))
+                    #:environment-variables
+                    (list (string-append "ELOGIND_CONF_FILE="
+                                         #$(elogind-configuration-file
+                                            config))))))
+                ;; Wait until the login1 service name has been acquired by
+                ;; D-Bus.  This prevents potential races that would cause
+                ;; elogind to be auto started by D-Bus by other processes
+                ;; requiring it, causing problems.
+                (parameterize ((%send-dbus-bus (string-append "unix:path="
+                                                              %dbus-system-bus)))
+                  (with-retries 25 1
+                    (pk 'available-dbus-services (dbus-available-services))
+                    (dbus-service-available? "org.freedesktop.login1")))
+
+                pid)))
          (stop #~(make-kill-destructor)))))
 
 (define elogind-service-type
-- 
2.34.0