Qt4: fix Genode thread deletion

With this patch the Genode thread used by the QThread class gets deleted
when 'QThread::wait()' gets called and the timeout didn't trigger or when
'QThread::terminate()' gets called.

Fixes #193.

qt4/src/lib/qt4/qt4_genode.patch

@@ -870,7 +870,7 @@ diff --git a/src/corelib/thread/qthread_p.h b/src/corelib/thread/qthread_p.h
  #include "qplatformdefs.h"
  #include "QtCore/qthread.h"
  #include "QtCore/qmutex.h"
-@@ -136,6 +140,39 @@
+@@ -136,6 +140,56 @@
      static QThread *threadForId(int id);
  
  #ifdef Q_OS_UNIX
@@ -878,17 +878,34 @@ diff --git a/src/corelib/thread/qthread_p.h b/src/corelib/thread/qthread_p.h
 +
 +    class Genode_thread : public Genode::Thread_qt
 +    {
++        private:
++
++    	    /*
++    	     * The '_finished_lock' is necessary because 'QThreadPrivate::mutex'
++    	     * uses a 'Genode::Timed_semaphore' internally and it isn't safe
++    	     * to delete a Genode thread that just called 'Semaphore::up()',
++    	     * because the 'Semaphore::_meta_lock' could still be locked.
++    	     */
++            Genode::Lock _finished_lock;
++            QThread *_qthread;
++
 +        public:
-+        Genode_thread(QThread *qthread) : _qthread(qthread) { }
++
++            Genode_thread(QThread *qthread)
++            : _finished_lock(Genode::Lock::LOCKED),
++              _qthread(qthread) { }
 +
 +            virtual void entry()
 +            {
 +                QThreadPrivate::start(_qthread);
 +                QThreadPrivate::finish(_qthread);
++                _finished_lock.unlock();
 +            }
 +
-+      private:
-+        QThread *_qthread;
++            void join()
++            {
++                _finished_lock.lock();
++            }
 +    };
 +
 +    Genode_thread *genode_thread;
@@ -910,7 +927,7 @@ diff --git a/src/corelib/thread/qthread_p.h b/src/corelib/thread/qthread_p.h
      pthread_t thread_id;
      QWaitCondition thread_done;
  
-@@ -145,6 +182,7 @@
+@@ -145,6 +199,7 @@
  #else
      static void finish(void *);
  #endif

qt4/src/lib/qt4/src/corelib/thread/qthread_genode.cpp

@@ -337,14 +337,28 @@ void QThread::terminate()
     QMutexLocker locker(&d->mutex);
 
     if (QThreadPrivate::tls.value(QThread::currentThreadId()).termination_enabled) {
+
+        if (d->genode_thread) {
             delete d->genode_thread;
             d->genode_thread = 0;
+        }
 
         d->terminated = true;
         d->running = false;
     }
 }
 
+
+static inline void join_and_delete_genode_thread(QThreadPrivate *d)
+{
+    if (d->genode_thread) {
+        d->genode_thread->join();
+        delete d->genode_thread;
+        d->genode_thread = 0;
+    }
+}
+
+
 /*!
     Blocks the thread until either of these conditions is met:
 
@@ -374,14 +388,18 @@ bool QThread::wait(unsigned long time)
         return false;
     }
 
-    if (d->finished || !d->running)
+    if (d->finished || !d->running) {
+        join_and_delete_genode_thread(d);
         return true;
+    }
 
     while (d->running) {
         if (!d->thread_done.wait(locker.mutex(), time))
             return false;
     }
 
+    join_and_delete_genode_thread(d);
+
     return true;
 }
 

qt4/src/lib/qt4/src/corelib/thread/qwaitcondition_genode.cpp

@@ -251,10 +251,10 @@ bool QWaitCondition::wait(QMutex *mutex, unsigned long time)
     } else {
     	try {
     	  d->sem.down((Genode::Alarm::Time) time);
+          result = true;
     	} catch (Genode::Timeout_exception) {
-    		return false;
+          result = false;
     	}
-    	return true;
     }
     
     mutex->lock();