Better fix for error on restart

Now both single instance and listener mutexes are explicitly released
before launching child process, so the child process has no need to wait
for the parent process to die.

src/calibre/gui2/main.py

@@ -30,6 +30,7 @@ from calibre.utils.lock import SingleInstance
 from calibre.utils.monotonic import monotonic
 from polyglot.builtins import as_bytes, environ_item, range, unicode_type
 
+after_quit_actions = {'debug_on_restart': False, 'restart_after_quit': False}
 if iswindows:
     winutil = plugins['winutil'][0]
 
@@ -353,27 +354,18 @@ class GuiRunner(QObject):
         self.initialize_db()
 
 
-def set_restarting_env_var():
-    if iswindows:
-        ctime = winutil.get_process_times(None)[0]
-        os.environ['CALIBRE_RESTARTING_FROM_GUI'] = str(ctime)
-    else:
-        os.environ['CALIBRE_RESTARTING_FROM_GUI'] = str(os.getpid())
-
-
 def run_in_debug_mode():
     from calibre.debug import run_calibre_debug
     import tempfile, subprocess
     fd, logpath = tempfile.mkstemp('.txt')
     os.close(fd)
-    set_restarting_env_var()
     run_calibre_debug(
         '--gui-debug', logpath, stdout=lopen(logpath, 'wb'),
         stderr=subprocess.STDOUT, stdin=lopen(os.devnull, 'rb'))
 
 
 def run_gui(opts, args, listener, app, gui_debug=None):
-    with SingleInstance('db') as si:
+    with listener, SingleInstance('db') as si:
         if not si:
             ext = '.exe' if iswindows else ''
             error_dialog(None, _('Cannot start calibre'), _(
@@ -404,31 +396,8 @@ def run_gui_(opts, args, listener, app, gui_debug=None):
         from calibre.gui2.wizard import wizard
         wizard().exec_()
     if getattr(runner.main, 'restart_after_quit', False):
-        e = sys.executable if getattr(sys, 'frozen', False) else sys.argv[0]
-        if getattr(runner.main, 'debug_on_restart', False) or gui_debug is not None:
-            run_in_debug_mode()
-        else:
-            if hasattr(sys, 'frameworks_dir'):
-                app = os.path.dirname(os.path.dirname(os.path.realpath(sys.frameworks_dir)))
-                from calibre.debug import run_calibre_debug
-                prints('Restarting with:', app)
-                run_calibre_debug('-c', 'import sys, os, time; time.sleep(3); os.execlp("open", "open", sys.argv[-1])', app)
-            else:
-                import subprocess
-                set_restarting_env_var()
-                if iswindows:
-                    winutil.prepare_for_restart()
-                if hasattr(sys, 'run_local'):
-                    cmd = [sys.run_local]
-                    if DEBUG:
-                        cmd += ['calibre-debug', '-g']
-                    else:
-                        cmd.append('calibre')
-                else:
-                    args = ['-g'] if os.path.splitext(e)[0].endswith('-debug') else []
-                    cmd = [e] + args
-                prints('Restarting with:', ' '.join(cmd))
-                subprocess.Popen(cmd)
+        after_quit_actions['restart_after_quit'] = True
+        after_quit_actions['debug_on_restart'] = getattr(runner.main, 'debug_on_restart', False) or gui_debug is not None
     else:
         if iswindows:
             try:
@@ -436,7 +405,6 @@ def run_gui_(opts, args, listener, app, gui_debug=None):
             except:
                 pass
     if getattr(runner.main, 'gui_debug', None) is not None:
-        e = sys.executable if getattr(sys, 'frozen', False) else sys.argv[0]
         debugfile = runner.main.gui_debug
         from calibre.gui2 import open_local_file
         if iswindows:
@@ -527,30 +495,36 @@ def create_listener():
     return Listener(address=gui_socket_address())
 
 
-def wait_for_parent_to_die(ppid, max_wait=10):
-    ppid = int(ppid)
+def restart_after_quit():
     if iswindows:
-
-        def parent_done():
-            try:
-                ctime = winutil.get_process_times(os.getppid())[0]
-            except Exception:
-                return True
-            return ctime > ppid
-
+        # detach the stdout/stderr/stdin handles
+        winutil.prepare_for_restart()
+    if after_quit_actions['debug_on_restart']:
+        run_in_debug_mode()
+        return
+    if hasattr(sys, 'frameworks_dir'):
+        app = os.path.dirname(os.path.dirname(os.path.realpath(sys.frameworks_dir)))
+        from calibre.debug import run_calibre_debug
+        prints('Restarting with:', app)
+        run_calibre_debug('-c', 'import sys, os, time; time.sleep(3); os.execlp("open", "open", sys.argv[-1])', app)
     else:
-        def parent_done():
-            return os.getppid() != ppid
-
-    st = time.monotonic()
-    while not parent_done() and time.monotonic() - st < max_wait:
-        time.sleep(0.1)
+        import subprocess
+        if hasattr(sys, 'run_local'):
+            cmd = [sys.run_local]
+            if DEBUG:
+                cmd += ['calibre-debug', '-g']
+            else:
+                cmd.append('calibre')
+        else:
+            e = sys.executable if getattr(sys, 'frozen', False) else sys.argv[0]
+            cmd = [e]
+            if os.path.splitext(e)[0].endswith('-debug'):
+                cmd.append('-g')
+        prints('Restarting with:', ' '.join(cmd))
+        subprocess.Popen(cmd)
 
 
 def main(args=sys.argv):
-    ppid = os.environ.pop('CALIBRE_RESTARTING_FROM_GUI', None)
-    if ppid is not None:
-        wait_for_parent_to_die(ppid)
     if iswindows and 'CALIBRE_REPAIR_CORRUPTED_DB' in os.environ:
         windows_repair()
         return 0
@@ -567,6 +541,8 @@ def main(args=sys.argv):
         if si and opts.shutdown_running_calibre:
             return 0
         run_main(app, opts, args, gui_debug, si)
+    if after_quit_actions['restart_after_quit']:
+        restart_after_quit()
 
 
 def run_main(app, opts, args, gui_debug, si):