diff --git a/core/feature.h b/core/feature.h
index 5f72065..2ebd4a7 100644
--- a/core/feature.h
+++ b/core/feature.h
@@ -13,6 +13,7 @@
 #include "config.h"
 
 // some older machines need this to see pselect
+#define _BSD_SOURCE 1
 #define _DEFAULT_SOURCE 1
 #define _XOPEN_SOURCE 700
 #define _DARWIN_C_SOURCE 1
diff --git a/core/observe.c b/core/observe.c
index df1df25..64e5aeb 100644
--- a/core/observe.c
+++ b/core/observe.c
@@ -8,6 +8,7 @@
 */
 #include "feature.h"
 
+#include <sys/select.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <signal.h>
diff --git a/core/signal.c b/core/signal.c
index 8cab0cd..9466a51 100644
--- a/core/signal.c
+++ b/core/signal.c
@@ -271,5 +271,12 @@ signal_notify(
 
 	if( lua_pcall( L, 1, 0, -3 ) ) exit( -1 );
 	lua_pop( L, 1 );
+
+	if( lua_gettop( L ) )
+	{
+		logstring( "Error", "internal, stack is dirty." );
+		l_stackdump( L );
+		exit( -1 );
+	}
 }
 
diff --git a/default/signal.lua b/default/signal.lua
index 70835ce..a3a8583 100644
--- a/default/signal.lua
+++ b/default/signal.lua
@@ -14,6 +14,17 @@ if not default then error( 'default not loaded' ) end
 default.signal = { }
 
 
+--
+--
+--
+local function onCollect
+(
+	sync -- the user intf to the sync a child finished for
+)
+
+end
+
+
 local function sighup
 ( )
 	print( 'GOT A HUP SIGNAL' )
@@ -26,12 +37,18 @@ local function sigint
 ( )
 	print( 'GOT AN INT SIGNAL' )
 
-	for _, s in ipairs( syncs )
+	for _, sync in ipairs( syncs )
 	do
-		print( 'a sync' )
-	end
+		sync.stop( )
 
-	os.exit( 1 )
+		if( #sync.pids == 0 )
+		then
+			syncs.remove( sync )
+		else
+			sync.onCollect( onCollect )
+		end
+	end
+--	os.exit( 1 )
 end
 
 
@@ -55,6 +72,8 @@ init =
 	local int = getsignal( 'INT' )
 	local term = getsignal( 'TERM' )
 
+	print( 'INIT', hup, int, term )
+
 	if hup ~= false then hup = sighup end
 	if int ~= false then int = sigint end
 	if term ~= false then term = sigterm end
@@ -62,6 +81,6 @@ init =
 	onsignal(
 		'HUP', hup,
 		'INT', int,
-		'TERM', iterm
+		'TERM', term
 	)
 end
diff --git a/mantle/signal.lua b/mantle/signal.lua
index 0bdf15b..c841145 100644
--- a/mantle/signal.lua
+++ b/mantle/signal.lua
@@ -95,7 +95,7 @@ function onsignal
 
 	if n % 2 ~= 0
 	then
-		error( 'onsignal with uneven number of arguments called', 2 )
+		error( 'onsignal() with uneven number of arguments called', 2 )
 	end
 
 	for a = 1, n, 2
diff --git a/mantle/sync.lua b/mantle/sync.lua
index fda5845..1a3c5aa 100644
--- a/mantle/sync.lua
+++ b/mantle/sync.lua
@@ -204,6 +204,14 @@ local function collect
 	end
 
 	self.processes[ pid ] = nil
+
+	if self.onCollect
+	then
+		for _, func in ipairs( self.onCollect )
+		do
+			func( self:getUserIntf( ) )
+		end
+	end
 end
 
 
@@ -469,7 +477,8 @@ local function getAlarm
 (
 	self
 )
-	if #self.processes >= self.config.maxProcesses
+	if self.stopped
+	or #self.processes >= self.config.maxProcesses
 	then
 		return false
 	end
@@ -557,7 +566,8 @@ local function invokeActions
 )
 	log( 'Function', 'invokeActions( "', self.config.name, '", ', timestamp, ' )' )
 
-	if #self.processes >= self.config.maxProcesses
+	if self.stopped
+	or #self.processes >= self.config.maxProcesses
 	then
 		-- no new processes
 		return
@@ -731,13 +741,48 @@ local function getUserIntf
 
 	if ui then return ui end
 
-	ui = { muhkuh = true }
+	ui = {
+		-- Stops the sync, meaning no more
+		-- processes will be spawned
+		stop = function( )
+			self.stopped = true
+		end,
+
+		-- Registers an additional function to be called
+		-- after each collect.
+		--
+		-- Used by default signal handlers to wait
+		-- for children to finish (or react on forwarded signal)
+		onCollect = function( func )
+			if not self.onCollect
+			then
+				self.onCollect = { func }
+			else
+				table.insert( self.onCollect, func )
+			end
+		end,
+
+		-- Returns a list of pids of children
+		-- processes
+		pids = function
+		( )
+			local pids = { }
+
+			for k, v in pairs( self.processes )
+			do
+				pids[ k ] = v
+			end
+
+			return pids
+		end,
+	}
 
 	self.userIntf = ui
 
 	return ui
 end
 
+
 --
 -- Creates a new Sync.
 --
@@ -748,11 +793,12 @@ local function new
 	local s =
 	{
 		-- fields
-		config = config,
-		delays = Queue.new( ),
-		source = config.source,
+		config    = config,
+		delays    = Queue.new( ),
+		source    = config.source,
 		processes = Counter.new( ),
-		filters = nil,
+		filters   = nil,
+		stopped   = false,
 
 		-- functions
 		addBlanketDelay = addBlanketDelay,
@@ -765,11 +811,13 @@ local function new
 		getAlarm        = getAlarm,
 		getDelays       = getDelays,
 		getNextDelay    = getNextDelay,
-		getUserIntf     = getUserIntf,
 		invokeActions   = invokeActions,
 		removeDelay     = removeDelay,
 		rmExclude       = rmExclude,
 		statusReport    = statusReport,
+
+		-- use interface
+		getUserIntf     = getUserIntf,
 	}
 
 	s.inlet = InletFactory.newInlet( s )
diff --git a/mantle/syncmaster.lua b/mantle/syncmaster.lua
index e0fe53a..c1d71e2 100644
--- a/mantle/syncmaster.lua
+++ b/mantle/syncmaster.lua
@@ -77,7 +77,7 @@ end
 --
 local function get
 ( i )
-	return syncList[ i ];
+	return syncList[ i ]
 end
 
 --
diff --git a/mantle/user.lua b/mantle/user.lua
index 510d7fd..8224ffe 100644
--- a/mantle/user.lua
+++ b/mantle/user.lua
@@ -266,23 +266,38 @@ user.syncs =
 	-- iterator for user syncs
 	function iter
 	(
-		self,
-		pos
+		self, -- the syncs list copy
+		pos   -- position
 	)
 		pos = pos + 1
 
-		if pos >= #SyncMaster then return nil end
+		local result = self[ pos ]
 
-		local sync = SyncMaster.get( pos )
+		if result == nil then return nil end
 
-		return pos, sync:getUserIntf( )
+		return pos, self[ pos ]
 	end
 
 	local mt = { }
 
+	--
+	-- This iterator will make a copy of the syncs at the moment
+	-- it is started, so the list can be manipulated while a loop
+	-- iterates through the copy.
+	--
 	mt.__ipairs =
-		function( self )
-			return iter, self, -1
+		function
+		(
+			self    -- is user.syncs
+		)
+			local list = { }
+
+			for k = 0, #SyncMaster - 1
+			do
+				list[ k ] = SyncMaster.get( k ):getUserIntf( )
+			end
+
+			return iter, list, -1
 		end
 
 	-- public interface