From d94357f98c46245c7c70efe006a7080f6cfe5aa8 Mon Sep 17 00:00:00 2001
From: Ivailo Monev <xakepa10@gmail.com>
Date: Sat, 9 Apr 2022 20:00:56 +0300
Subject: [PATCH] kgreeter: kill lightdm process at exit and before starting it
 again from KCM

Signed-off-by: Ivailo Monev <xakepa10@gmail.com>
---
 kgreeter/kcm/kgreeterconfig.cpp | 25 ++++++++++++++++++++++---
 kgreeter/kcm/kgreeterconfig.h   |  3 +++
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/kgreeter/kcm/kgreeterconfig.cpp b/kgreeter/kcm/kgreeterconfig.cpp
index 4091c24a..c6a73d4f 100644
--- a/kgreeter/kcm/kgreeterconfig.cpp
+++ b/kgreeter/kcm/kgreeterconfig.cpp
@@ -20,7 +20,6 @@
 
 #include <QSettings>
 #include <QStyleFactory>
-#include <QProcess>
 #include <kdebug.h>
 #include <kconfiggroup.h>
 #include <klocale.h>
@@ -33,6 +32,9 @@
 #include <kpluginfactory.h>
 #include <kpluginloader.h>
 
+#include <sys/types.h>
+#include <signal.h>
+
 #include "config-workspace.h"
 
 K_PLUGIN_FACTORY(KCMGreeterFactory, registerPlugin<KCMGreeter>();)
@@ -40,7 +42,8 @@ K_EXPORT_PLUGIN(KCMGreeterFactory("kcmgreeterconfig", "kcm_greeterconfig"))
 
 KCMGreeter::KCMGreeter(QWidget* parent, const QVariantList& args)
     : KCModule(KCMGreeterFactory::componentData(), parent),
-    m_lightdmexe(KStandardDirs::findRootExe("lightdm"))
+    m_lightdmexe(KStandardDirs::findRootExe("lightdm")),
+    m_lightdmpid(0)
 {
     Q_UNUSED(args);
 
@@ -99,6 +102,7 @@ KCMGreeter::KCMGreeter(QWidget* parent, const QVariantList& args)
 
 KCMGreeter::~KCMGreeter()
 {
+    killLightDM();
 }
 
 void KCMGreeter::load()
@@ -207,7 +211,15 @@ void KCMGreeter::slotURLChanged(const KUrl &url)
 
 void KCMGreeter::slotTest()
 {
-    if (!QProcess::startDetached(m_lightdmexe, QStringList() << QString::fromLatin1("--test-mode"))) {
+    killLightDM();
+
+    const bool result = QProcess::startDetached(
+        m_lightdmexe,
+        QStringList() << QString::fromLatin1("--test-mode"),
+        QDir::currentPath(),
+        &m_lightdmpid
+    );
+    if (!result) {
         KMessageBox::error(this, i18n("Could not start LightDM"));
     }
 }
@@ -221,4 +233,11 @@ void KCMGreeter::enableTest(const bool enable)
     }
 }
 
+void KCMGreeter::killLightDM()
+{
+    if (m_lightdmpid > 0) {
+        ::kill(pid_t(m_lightdmpid), SIGTERM);
+    }
+}
+
 #include "moc_kgreeterconfig.cpp"
diff --git a/kgreeter/kcm/kgreeterconfig.h b/kgreeter/kcm/kgreeterconfig.h
index 13ca4bd4..fa234f52 100644
--- a/kgreeter/kcm/kgreeterconfig.h
+++ b/kgreeter/kcm/kgreeterconfig.h
@@ -19,6 +19,7 @@
 #ifndef KGREETERCONFIG_H
 #define KGREETERCONFIG_H
 
+#include <QProcess>
 #include <kcmodule.h>
 
 #include "ui_kgreeterconfig.h"
@@ -51,8 +52,10 @@ private Q_SLOTS:
 
 private:
     void enableTest(const bool enable);
+    void killLightDM();
 
     QString m_lightdmexe;
+    Q_PID m_lightdmpid;
 };
 
 #endif // KGREETERCONFIG_H