diff --git a/apps/emqttd/src/emqttd_cm.erl b/apps/emqttd/src/emqttd_cm.erl
index 90091ee14..b0ec49ed5 100644
--- a/apps/emqttd/src/emqttd_cm.erl
+++ b/apps/emqttd/src/emqttd_cm.erl
@@ -86,7 +86,8 @@ lookup(ClientId) when is_binary(ClientId) ->
 %%------------------------------------------------------------------------------
 -spec register(ClientId :: binary(), Pid :: pid()) -> ok.
 register(ClientId, Pid) when is_binary(ClientId), is_pid(Pid) ->
-	gen_server:call(?SERVER, {register, ClientId, Pid}).
+    %%TODO: infinify to block requests when too many clients, this will be redesinged in 0.9.x...
+	gen_server:call(?SERVER, {register, ClientId, Pid}, infinity).
 
 %%------------------------------------------------------------------------------
 %% @doc
diff --git a/apps/emqttd/src/emqttd_pubsub.erl b/apps/emqttd/src/emqttd_pubsub.erl
index 67b841dd8..db990d871 100644
--- a/apps/emqttd/src/emqttd_pubsub.erl
+++ b/apps/emqttd/src/emqttd_pubsub.erl
@@ -119,8 +119,12 @@ create(Topic) ->
 subscribe({Topic, Qos}, SubPid) when is_binary(Topic) and is_pid(SubPid) ->
     subscribe([{Topic, Qos}], SubPid);
 
+%% TODO: 
+%% call will not work when there are 2000K+ clients, 100+ sub requests/sec...
+%% will optimize in 0.9.x...
+%% 
 subscribe(Topics, SubPid) when is_list(Topics) and is_pid(SubPid) ->
-    gen_server:call(?SERVER, {subscribe, Topics, SubPid}).
+    gen_server:call(?SERVER, {subscribe, Topics, SubPid}, infinity).
 
 %%------------------------------------------------------------------------------
 %% @doc