Give up on proper signal handling

docs/api.rst

@@ -21,7 +21,7 @@ General Section
   next sync. The data is needed to determine whether a new item means it has
   been added on one side or deleted on the other.
 
-- ``processes``: Optional, defines the amount of maximal connections to use for
+- ``processes``: Optional, defines the maximal amount of threads to use for
   syncing.  By default there is no limit, which means vdirsyncer will try to
   open a connection for each collection to be synced. The value ``0`` is
   ignored. Setting this to ``1`` will only synchronize one collection at a
@@ -32,6 +32,12 @@ General Section
   Raspberry Pi is so slow that multiple connections don't help much, since the
   CPU and not the network is the bottleneck.
 
+  .. note::
+
+      Due to restrictions in Python's threading module, setting ``processes``
+      to anything else than ``1`` will mean that you can't properly abort the
+      program with ``^C`` anymore.
+
 .. _pair_config:
 
 Pair Section

vdirsyncer/cli.py

@@ -357,9 +357,7 @@ def _create_app():
             from multiprocessing.dummy import Pool
             p = Pool(processes=general.get('processes', 0) or len(actions))
 
-            # We have to use map_async.get(large_value) instead of map or
-            # map_async.get() because otherwise ^C wouldn't work properly.
-            rv = p.map_async(_sync_collection, actions).get(10**9)
+            rv = p.imap_unordered(_sync_collection, actions)
 
         if not all(rv):
             sys.exit(1)