I have a simple GUI app where clicking a Start button, the start button gets disabled, a few asterisks get printed, then at the end, start button gets re-enabled.

After threaded function completes, I should see this:
finished.png

But maybe 3/5 times, it will just stay stuck here forever:
python_error.png

This intermittent issue only happens in Linux (CentOs 6.7). Windows is fine. Anyone have any ideas, this is so weird. Thanks!!


Qt Code: 
  1. #!/usr/bin/env python2
  2.  
  3. import sys, time
  4. from PySide.QtGui import *
  5. from PySide import QtCore
  6.  
  7. class BcProcessing(QtCore.QObject):
  8.     finished = QtCore.Signal()
  9.  
  10.     def __init__(self, parent = None):
  11.         super(BcProcessing, self).__init__(parent)
  12.         self._isRunning = True
  13.  
  14.     def outputAsterisks(self):
  15.         end = time.time()+3
  16.         self._isRunning = True
  17.         while self._isRunning == True:
  18.             sys.stdout.write('*')
  19.             sys.stdout.flush()
  20.             time.sleep(1)
  21.             now = time.time()
  22.             if now>=end:        
  23.                 self._isRunning=False
  24.         self.finished.emit()
  25.  
  26. class MainWindow(QMainWindow):
  27.         def __init__(self, parent=None):
  28.                 QMainWindow.__init__(self,parent)
  29.                 centralwidget = QWidget(self)
  30.                 startButton = QPushButton('Start long (3 seconds) operation',self)
  31.                 label2 = QLabel('Hello')
  32.                 vbox = QVBoxLayout()
  33.                 vbox.addWidget(startButton)
  34.                 vbox.addWidget(label2)
  35.                 self.setCentralWidget(centralwidget)
  36.                 centralwidget.setLayout(vbox)
  37.  
  38.                 self.testObj = BcProcessing()
  39.                 self.newThread = QtCore.QThread()
  40.                 self.testObj.moveToThread(self.newThread)
  41.                 self.newThread.started.connect(self.testObj.outputAsterisks)    
  42.  
  43.                 def closingThread():
  44.                     if self.newThread.isRunning():
  45.                         print 'closing running threads...'
  46.                         self.newThread.quit()
  47.                         self.newThread.wait()
  48.  
  49.                 def LongOperationStart():
  50.                         label2.setText('app is running...')
  51.                         startButton.setEnabled(False)
  52.                         self.newThread.start()
  53.  
  54.                 #Sometimes this does not get called in Linux!
  55.                 def LongOperationFinish():
  56.                         label2.setText('app finished')
  57.                         startButton.setEnabled(True)
  58.                         closingThread()
  59.  
  60.                 #GUI start button
  61.                 startButton.clicked.connect(LongOperationStart)
  62.  
  63.                 self.testObj.finished.connect(LongOperationFinish)
  64.  
  65.                 #On GUI window exiting, clean up threads   
  66.                 app.aboutToQuit.connect(closingThread)
  67.  
  68.  
  69. if __name__=='__main__':
  70.         app = QApplication(sys.argv)
  71.         print 'asdf', app.aboutQt()
  72.         window = MainWindow()
  73.         window.show()
  74.         sys.exit(app.exec_())
To copy to clipboard, switch view to plain text mode