Exit "infinite" monitorloop when SyncRunner thread exits

The huge UI rework patch removed some obscure logic and special handling of
thread exit messages. It turns out that this was in fact still needed as a
specific exit message of the SyncRunner thread signified the threatmonitor
to quit.

We will want a nicer machinery for this in the future I guess, but fix the
eternal hang on exit by reintroducing a special exit message for the
SyncRunner thread, and return from the infinite monitor loop if SyncRunner
finishes.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

offlineimap/syncmaster.py

@@ -30,6 +30,8 @@ def syncaccount(threads, config, accountname):
     threads.add(thread)
 
 def syncitall(accounts, config):
+    # Special exit message for SyncRunner thread, so main thread can exit
+    currentThread().exit_message = 'SYNCRUNNER_EXITED_NORMALLY'
     threads = threadlist()
     for accountname in accounts:
         syncaccount(threads, config, accountname)

offlineimap/threadutil.py

@@ -95,19 +95,23 @@ def exitnotifymonitorloop(callback):
     :type callback:  a callable function
     """
     global exitthreads
-    while 1:
+    do_loop = True
+    while do_loop:
         # Loop forever and call 'callback' for each thread that exited
         try:
             # we need a timeout in the get() call, so that ctrl-c can throw
             # a SIGINT (http://bugs.python.org/issue1360). A timeout with empty
             # Queue will raise `Empty`.
             thrd = exitthreads.get(True, 60)
-            callback(thrd)
+            # request to abort when callback returns true
+            do_loop = (callback(thrd) != True)
         except Empty:
             pass
 
 def threadexited(thread):
-    """Called when a thread exits."""
+    """Called when a thread exits.
+
+    Main thread is aborted when this returns True."""
     ui = getglobalui()
     if thread.exit_exception:
         if isinstance(thread.exit_exception, SystemExit):
@@ -117,12 +121,11 @@ def threadexited(thread):
             raise SystemExit
         ui.threadException(thread)      # Expected to terminate
         sys.exit(100)                   # Just in case...
-    elif thread.exit_message == 'SYNC_WITH_TIMER_TERMINATE':
-        ui.terminate()
-        # Just in case...
-        sys.exit(100)
+    elif thread.exit_message == 'SYNCRUNNER_EXITED_NORMALLY':
+        return True
     else:
         ui.threadExited(thread)
+        return False
 
 class ExitNotifyThread(Thread):
     """This class is designed to alert a "monitor" to the fact that a