kdesktop: fix deadlock condition between kdesktop and kdesktop lock.

The logic to handle communication with kdesktop_lock is now running
completely in a separate thread and event loop, meaning the main GUI
thread remains responsive all the time and can handle interaction with
X11, DCOP and DBUS calls. This resolves issue #589.
The commit also solves the first problem reported in issue #640 and
loosely related to PR #526.

Signed-off-by: Michele Calgaro <michele.calgaro@yahoo.it>

kdesktop/DESIGN

@@ -124,3 +124,16 @@ kdesktop_lock to kdesktop communication:
    - TTIN: the lock process is ready. This is sent after the process has been created/respawned
    - USR2: the lock/screensaver has been activated
    - USR1: the lock/screensaver has been unlocked/stopped
+
+Communication is handled by the screen saver engine defined in 'lockeng.{h,cpp}'.
+The engine is split into two parts, the 'SaverEngine' running in the GUI thread and
+the 'SaverEngineEventHandler' running in a separate thread and eventloop.
+The 'SaverEngine' handles communication with X11, DCOP and DBUS while the
+'SaverEngineEventHandler' handles communication with the actual lock process.
+Several actions require cooperation of the two parts, so in various methods
+there will be inter-thread calls (using timers or by emitting signals) to
+trigger the other side remaining logic.
+This complex design is necessary to avoid blocking the main GUI application event loop,
+which has several tasks to manage and therefore can't affort to wait in a suspended state.
+This was previously leading to deadlock when DCOP calls where executed on the secondary
+thread/eventloop, for example when changing desktop while the lock process was restarting.

kdesktop/KScreensaverIface.h

@@ -12,11 +12,10 @@ public:
   KScreensaverIface() : DCOPObject("KScreensaverIface") {}
 
 k_dcop:
-  /** Lock the screen now even if the screensaver does not lock by default. */
+  /** Lock the screen now even if the screensaver does not lock by default */
   virtual void lock() = 0;
 
-  /** Save the screen now.  If the user has locking enabled, the screen is
+  /** Start the screensaver now. If the user has locking enabled, the screen is locked also */
-   * locked also. */
   virtual void save() = 0;
 
   /** Quit the screensaver if it is running */
@@ -34,11 +33,12 @@ k_dcop:
   /** Is the screen currently blanked? */
   virtual bool isBlanked() = 0;
 
-  /** Reload the screensaver configuration. */
+  /** Reload the screensaver configuration */
   virtual void configure() = 0;
 
-  /** Only blank the screen (and possibly lock).  Do not use a custom
+  /**
-   * screen saver in the interest of saving battery.
+   * Set the screensaver to blank (and possibly lock).
+   * This method does not actually start the screensaver.
    */
   virtual void setBlankOnly(bool blankOnly) = 0;
 

kdesktop/lock/lockprocess.h

@@ -106,9 +106,6 @@ class LockProcess : public TQWidget
 
 		TDECryptographicCardDevice* cryptographicCardDevice();
 
-	signals:
-		void terminateHelperThread();
-
 	public slots:
 		void quitSaver();
 		void preparePopup();

kdesktop/lockeng.h

@@ -1,6 +1,5 @@
-//===========================================================================
 //
-// This file is part of the KDE project
+// This file is part of the TDE project
 //
 // Copyright (c) 1999 Martin R. Jones <mjones@kde.org>
 //
@@ -8,7 +7,6 @@
 #ifndef __LOCKENG_H__
 #define __LOCKENG_H__
 
-#include <tqwidget.h>
 #include <tqthread.h>
 #include <tdeprocess.h>
 #include <tqvaluevector.h>
@@ -23,31 +21,48 @@ class TDECryptographicCardDevice;
 #else
 #define TDECryptographicCardDevice void
 #endif
+
+/**
+ * Screen saver engine. Handles communication with the lock process.
+ * The engine is split into two parts, the 'SaverEngine' running in the GUI thread and
+ * the 'SaverEngineEventHandler' running in a separate thread and eventloop.
+ * The 'SaverEngine' handles communication with X11, DCOP and DBUS while the
+ * 'SaverEngineEventHandler' handles communication with the actual lock process.
+ * Several actions require cooperation of the two parts, so in various methods
+ * there will be inter-thread calls (using timers or by emitting signals) to
+ * trigger the other side remaining logic.
+ * This complex design is necessary to avoid blocking the main GUI application event loop,
+ * which has several tasks to manage and therefore can't affort to wait in a suspended state.
+ * This was previously leading to deadlock when DCOP calls where executed on the secondary
+ * thread/eventloop, for example when changing desktop while the lock process was restarting.
+ */
+
 class DCOPClientTransaction;
 class TQT_DBusMessage;
 class TQT_DBusProxy;
+class SaverEngineEventHandler;
 
-class SaverEngineThreadHelperObject : public TQObject
+// Type of lock screen
+enum LockType : int
 {
-	TQ_OBJECT
+	DontLock = 0,
-	
+	DefaultLock,
-public slots:
+	ForceLock,
-	void terminateThread();
+	SecureDialog
-	void slotLockProcessWaiting();
+};
-	void slotLockProcessFullyActivated();
 
-signals:
+enum SaverState
-	void lockProcessWaiting();
+{
-	void lockProcessFullyActivated();
+	Waiting,
+	Preparing,
+	Engaging,
+	Saving
 };
 
-//===========================================================================
+class SaverEngine : public TQObject, public KScreensaverIface
-/**
- * Screen saver engine.  Handles screensaver window, starting screensaver
- * hacks, and password entry.
- */
-class SaverEngine : public TQWidget, public KScreensaverIface
 {
+	friend class SaverEngineEventHandler;
+
 	TQ_OBJECT
 public:
 	SaverEngine();
@@ -100,80 +115,53 @@ public:
 	 */
 	virtual void saverLockReady();
 
-	/**
-	 * @internal
-	 */
 	void lockScreen(bool DCOP = false);
 
-	/**
-	 * Called by KDesktop to wait for saver engage
-	 * @internal
-	 */
-	bool waitForLockEngage();
-
-	/**
-	 * @internal
-	 */
 	void lockScreenAndDoNewSession();
-
-	/**
-	 * @internal
-	 */
 	void lockScreenAndSwitchSession(int vt);
 
+	void enableExports(); // Enable wallpaper exports
+
 signals:
-	void terminateHelperThread();
+	void activateSaverOrLockSignal(LockType lock_type);
-	void asyncLock();
+	void lockScreenSignal(bool);
+	void terminateEventHandlerThread();
 
 public slots:
-	void slotLockProcessReady();
-	void lockProcessWaiting();
-	void lockProcessFullyActivated();
 	void handleDBusSignal(const TQT_DBusMessage&);
+	void terminateTDESession();
 
 protected slots:
 	void idleTimeout();
-	void lockProcessExited();
 
 private slots:
-	void handleSecureDialog();
-	void slotSAKProcessExited();
-
 	void cryptographicCardInserted(TDECryptographicCardDevice*);
 	void cryptographicCardRemoved(TDECryptographicCardDevice*);
-
-	/**
-	 * Enable wallpaper exports
-	 */
-	void enableExports();
-	void recoverFromHackingAttempt();
 	void cardStartupTimeout();
-
 	bool dBusReconnect();
 
+	// The following slots are invoked by corresponding methods named without the 'GUI' suffix
+	// in 'SaverEngineEventHandler' to complete the remaining X11 part of the actions
+	void activateSaverOrLockGUI();
+	void lockProcessFullyActivatedGUI();
+	void lockProcessWaitingGUI();
+	void lockScreenGUI();
+	void stopLockProcessGUI();
+
 private:
-	bool restartDesktopLockProcess();
 	void dBusClose();
 	bool dBusConnect();
 	void onDBusServiceRegistered(const TQString&);
 	void onDBusServiceUnregistered(const TQString&);
 
 protected:
-	enum SaverState { Waiting, Preparing, Engaging, Saving };
-	enum LockType { DontLock, DefaultLock, ForceLock, SecureDialog };
-	bool startLockProcess( LockType lock_type );
-	bool waitForLockProcessStart();
-	void stopLockProcess();
-	bool handleKeyPress(XKeyEvent *xke);
 	void processLockTransactions();
 	xautolock_corner_t applyManualSettings(int);
 
 protected:
 	bool mEnabled;
 
-	SaverState mState;
 	XAutoLock *mXAutoLock;
-	TDEProcess mLockProcess;
 	int mTimeout;
 
 	// the original X screensaver parameters
@@ -182,18 +170,14 @@ protected:
 	int mXBlanking;
 	int mXExposures;
 
-	bool mBlankOnly;  // only use the blanker, not the defined saver
 	TQValueVector< DCOPClientTransaction* > mLockTransactions;
 
 public:
-	SaverEngineThreadHelperObject* m_threadHelperObject;
+	bool mBlankOnly;  // only use the blanker, not the defined saver // protected
+	SaverEngineEventHandler *m_saverEngineEventHandler;
 
 private:
-	TQEventLoopThread* m_helperThread;
+	TQEventLoopThread* m_eventHandlerThread;
-	sigset_t mThreadBlockSet;
-	TDEProcess* mSAKProcess;
-	bool mTerminationRequested;
-	bool mSaverProcessReady;
 	bool mNewVTAfterLockEngage;
 	bool mValidCryptoCardInserted;
 	int mSwitchVTAfterLockEngage;
@@ -204,5 +188,43 @@ private:
 	TQT_DBusProxy *systemdSession;
 };
 
+class SaverEngineEventHandler : public TQObject
+{
+	TQ_OBJECT
+	
+public:
+	SaverEngineEventHandler(SaverEngine *engine);
+
+	SaverState getState() const { return m_state; }
+
+	void lockProcessExited();
+	void lockProcessFullyActivated();
+	void lockProcessReady();
+	void terminateLockProcess();
+
+public slots:
+	bool activateSaverOrLock(LockType lock_type);
+	void lockScreen(bool DCOP = false);
+	bool restartLockProcess();
+	void saveScreen();
+	void stopLockProcess();
+	void terminateThread();
+
+protected slots:
+	void slotLockProcessExited();
+	void slotSAKProcessExited();
+
+protected:
+	void startSAKProcess();
+
+	bool m_saverProcessReady;
+	bool m_lockProcessRestarting;
+	bool m_terminationRequest;
+	SaverState m_state;
+	SaverEngine *m_saverEngine;
+	TDEProcess *m_SAKProcess;
+	TDEProcess m_lockProcess;
+};
+
 #endif
 

kdesktop/main.cpp

@@ -71,7 +71,7 @@ static TDECmdLineOptions options[] =
 };
 
 bool argb_visual = false;
-KDesktopApp *myApp = NULL;
+KDesktopApp *myApp = nullptr;
 
 // -----------------------------------------------------------------------------
 
@@ -251,7 +251,7 @@ extern "C" TDE_EXPORT int kdemain( int argc, char **argv )
         else
             XCloseDisplay( dpy );
     }
-    if( myApp == NULL )
+    if (!myApp)
         myApp = new KDesktopApp;
 #else
     myApp = new KDesktopApp;
@@ -260,9 +260,6 @@ extern "C" TDE_EXPORT int kdemain( int argc, char **argv )
 
     KDesktopSettings::instance(kdesktop_name + "rc");
 
-    bool x_root_hack = args->isSet("x-root");
-    bool wait_for_kded = args->isSet("waitforkded");
-
     // This MUST be created before any widgets are created
     SaverEngine saver;
 
@@ -279,16 +276,15 @@ extern "C" TDE_EXPORT int kdemain( int argc, char **argv )
        myApp->config()->reparseConfiguration();
     }
 
-    // for the KDE-already-running check in starttde
+    // for the TDE-already-running check in starttde
-    TDESelectionOwner kde_running( "_KDE_RUNNING", 0 );
+    TDESelectionOwner tde_running( "_KDE_RUNNING", 0 );
-    kde_running.claim( false );
+    tde_running.claim( false );
 
+    bool x_root_hack = args->isSet("x-root");
+    bool wait_for_kded = args->isSet("waitforkded");
     KDesktop desktop( &saver, x_root_hack, wait_for_kded );
 
     args->clear();
-
     myApp->dcopClient()->setDefaultObject( "KDesktopIface" );
-
-	
     return myApp->exec();
 }