Disable automatic garbage collection, instead ensure garbage collection runs only in the GUI thread

src/calibre/gui2/main_window.py

@@ -1,10 +1,14 @@
+from __future__ import (unicode_literals, division, absolute_import,
+                        print_function)
+
 __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import StringIO, traceback, sys
 
-from PyQt4.Qt import QMainWindow, QString, Qt, QFont, QCoreApplication, SIGNAL,\
+import StringIO, traceback, sys, gc
-                     QAction, QMenu, QMenuBar, QIcon, pyqtSignal
+
+from PyQt4.Qt import QMainWindow, QString, Qt, QFont, QTimer, \
+                     QAction, QMenu, QMenuBar, QIcon, pyqtSignal, QObject
 from calibre.gui2.dialogs.conversion_error import ConversionErrorDialog
 from calibre.utils.config import OptionParser
 from calibre.gui2 import error_dialog
@@ -35,6 +39,53 @@ class DebugWindow(ConversionErrorDialog):
     def flush(self):
         pass
 
+class GarbageCollector(QObject):
+
+    '''
+    Disable automatic garbage collection and instead collect manually
+    every INTERVAL milliseconds.
+
+    This is done to ensure that garbage collection only happens in the GUI
+    thread, as otherwise Qt can crash.
+    '''
+
+    INTERVAL = 5000
+
+    def __init__(self, parent, debug=False):
+        QObject.__init__(self, parent)
+        self.debug = debug
+
+        self.timer = QTimer(self)
+        self.timer.timeout.connect(self.check)
+
+        self.threshold = gc.get_threshold()
+        gc.disable()
+        self.timer.start(self.INTERVAL)
+        #gc.set_debug(gc.DEBUG_SAVEALL)
+
+    def check(self):
+        #return self.debug_cycles()
+        l0, l1, l2 = gc.get_count()
+        if self.debug:
+            print ('gc_check called:', l0, l1, l2)
+        if l0 > self.threshold[0]:
+            num = gc.collect(0)
+            if self.debug:
+                print ('collecting gen 0, found:', num, 'unreachable')
+            if l1 > self.threshold[1]:
+                num = gc.collect(1)
+                if self.debug:
+                    print ('collecting gen 1, found:', num, 'unreachable')
+                if l2 > self.threshold[2]:
+                    num = gc.collect(2)
+                    if self.debug:
+                        print ('collecting gen 2, found:', num, 'unreachable')
+
+    def debug_cycles(self):
+        gc.collect()
+        for obj in gc.garbage:
+            print (obj, repr(obj), type(obj))
+
 class MainWindow(QMainWindow):
 
     ___menu_bar = None
@@ -64,19 +115,15 @@ class MainWindow(QMainWindow):
         quit_action.setMenuRole(QAction.QuitRole)
         return preferences_action, quit_action
 
-    def __init__(self, opts, parent=None):
+    def __init__(self, opts, parent=None, disable_automatic_gc=False):
         QMainWindow.__init__(self, parent)
-        app = QCoreApplication.instance()
+        if disable_automatic_gc:
-        if app is not None:
+            self._gc = GarbageCollector(self, debug=False)
-            self.connect(app, SIGNAL('unixSignal(int)'), self.unix_signal)
         if getattr(opts, 'redirect', False):
             self.__console_redirect = DebugWindow(self)
             sys.stdout = sys.stderr = self.__console_redirect
             self.__console_redirect.show()
 
-    def unix_signal(self, signal):
-        print 'Received signal:', repr(signal)
-
     def unhandled_exception(self, type, value, tb):
         if type == KeyboardInterrupt:
             self.keyboard_interrupt.emit()

src/calibre/gui2/ui.py

@@ -9,7 +9,7 @@ __docformat__ = 'restructuredtext en'
 
 '''The main GUI'''
 
-import collections, os, sys, textwrap, time
+import collections, os, sys, textwrap, time, gc
 from Queue import Queue, Empty
 from threading import Thread
 from PyQt4.Qt import Qt, SIGNAL, QTimer, QHelpEvent, QAction, \
@@ -95,7 +95,7 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin, # {{{
 
 
     def __init__(self, opts, parent=None, gui_debug=None):
-        MainWindow.__init__(self, opts, parent)
+        MainWindow.__init__(self, opts, parent=parent, disable_automatic_gc=True)
         self.opts = opts
         self.device_connected = None
         self.gui_debug = gui_debug
@@ -298,6 +298,9 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin, # {{{
                     raise
         self.device_manager.set_current_library_uuid(db.library_id)
 
+        # Collect cycles now
+        gc.collect()
+
         if show_gui and self.gui_debug is not None:
             info_dialog(self, _('Debug mode'), '<p>' +
                     _('You have started calibre in debug mode. After you '
@@ -399,6 +402,7 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin, # {{{
         elif msg.startswith('refreshdb:'):
             self.library_view.model().refresh()
             self.library_view.model().research()
+            self.tags_view.recount()
         else:
             print msg
 
@@ -465,7 +469,6 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin, # {{{
         self.device_manager.set_current_library_uuid(db.library_id)
         # Run a garbage collection now so that it does not freeze the
         # interface later
-        import gc
         gc.collect()