Unblock signals in child processes

We need to unblock the signals blocked with pthread_sigmask.
This caused kdeinit to block, because it relies on SIGUSR1.

BUG: 356580
FIXED-IN: 5.5.1
REVIEW: 126361

main_wayland.cpp

@@ -197,7 +197,7 @@ void ApplicationWayland::continueStartupWithX()
             environment.insert(QStringLiteral("QT_QPA_PLATFORM"), QStringLiteral("wayland"));
             environment.remove("DISPLAY");
             environment.remove("WAYLAND_DISPLAY");
-            QProcess *p = new QProcess(this);
+            QProcess *p = new Process(this);
             p->setProcessChannelMode(QProcess::ForwardedErrorChannel);
             auto finishedSignal = static_cast<void (QProcess::*)(int, QProcess::ExitStatus)>(&QProcess::finished);
             connect(p, finishedSignal, this,
@@ -217,7 +217,7 @@ void ApplicationWayland::continueStartupWithX()
     m_environment.insert(QStringLiteral("DISPLAY"), QString::fromUtf8(qgetenv("DISPLAY")));
     // start session
     if (!m_sessionArgument.isEmpty()) {
-        QProcess *p = new QProcess(this);
+        QProcess *p = new Process(this);
         p->setProcessChannelMode(QProcess::ForwardedErrorChannel);
         p->setProcessEnvironment(m_environment);
         auto finishedSignal = static_cast<void (QProcess::*)(int, QProcess::ExitStatus)>(&QProcess::finished);
@@ -229,7 +229,7 @@ void ApplicationWayland::continueStartupWithX()
         for (const QString &application: m_applicationsToStart) {
             // note: this will kill the started process when we exit
             // this is going to happen anyway as we are the wayland and X server the app connects to
-            QProcess *p = new QProcess(this);
+            QProcess *p = new Process(this);
             p->setProcessChannelMode(QProcess::ForwardedErrorChannel);
             p->setProcessEnvironment(m_environment);
             p->start(application);
@@ -299,7 +299,7 @@ void ApplicationWayland::startXwaylandServer()
 
     m_xcbConnectionFd = sx[0];
 
-    m_xwaylandProcess = new QProcess(kwinApp());
+    m_xwaylandProcess = new Process(kwinApp());
     m_xwaylandProcess->setProcessChannelMode(QProcess::ForwardedErrorChannel);
     m_xwaylandProcess->setProgram(QStringLiteral("Xwayland"));
     QProcessEnvironment env = m_environment;

rules.cpp

@@ -1007,7 +1007,7 @@ void RuleBook::edit(AbstractClient* c, bool whole_app)
     args << QStringLiteral("--wid") << QString::number(c->window());
     if (whole_app)
         args << QStringLiteral("--whole-app");
-    QProcess *p = new QProcess(this);
+    QProcess *p = new Process(this);
     p->setArguments(args);
     p->setProcessEnvironment(kwinApp()->processStartupEnvironment());
     p->setProgram(QStringLiteral(KWIN_RULES_DIALOG_BIN));

useractions.cpp

@@ -330,7 +330,7 @@ void UserActionsMenu::init()
                 // opens the KWin configuration
                 QStringList args;
                 args << QStringLiteral("--icon") << QStringLiteral("preferences-system-windows") << configModules(false);
-                QProcess *p = new QProcess(this);
+                QProcess *p = new Process(this);
                 p->setArguments(args);
                 p->setProcessEnvironment(kwinApp()->processStartupEnvironment());
                 p->setProgram(QStringLiteral("kcmshell5"));

utils.cpp

@@ -42,6 +42,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "atoms.h"
 #include "workspace.h"
 
+#include <signal.h>
+
 #endif
 
 Q_LOGGING_CATEGORY(KWIN_CORE, "kwin_core", QtCriticalMsg)
@@ -142,6 +144,22 @@ void ungrabXKeyboard()
     xcb_ungrab_keyboard(connection(), XCB_TIME_CURRENT_TIME);
 }
 
+Process::Process(QObject *parent)
+    : QProcess(parent)
+{
+}
+
+Process::~Process() = default;
+
+void Process::setupChildProcess()
+{
+    sigset_t userSiganls;
+    sigemptyset(&userSiganls);
+    sigaddset(&userSiganls, SIGUSR1);
+    sigaddset(&userSiganls, SIGUSR2);
+    pthread_sigmask(SIG_UNBLOCK, &userSiganls, nullptr);
+}
+
 #endif
 
 // converting between X11 mouse/keyboard state mask and Qt button/keyboard states

utils.h

@@ -35,6 +35,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QPoint>
 #include <QRect>
 #include <QScopedPointer>
+#include <QProcess>
 // system
 #include <limits.h>
 Q_DECLARE_LOGGING_CATEGORY(KWIN_CORE)
@@ -227,6 +228,20 @@ private:
     bool m_valid = false;
 };
 
+/**
+ * QProcess subclass which unblocks SIGUSR in the child process.
+ **/
+class KWIN_EXPORT Process : public QProcess
+{
+    Q_OBJECT
+public:
+    explicit Process(QObject *parent = nullptr);
+    virtual ~Process();
+
+protected:
+    void setupChildProcess() override;
+};
+
 } // namespace
 
 // Must be outside namespace