From f9eeab89a2c72b601161bccac36e970341462001 Mon Sep 17 00:00:00 2001
From: Feng Lee <ery.lee@gmail.com>
Date: Sun, 16 Aug 2015 22:01:04 +0800
Subject: [PATCH] fix gen_server2 issue,
 https://github.com/rabbitmq/rabbitmq-server/issues/268

---
 src/emqttd_retained.erl | 2 +-
 src/emqttd_session.erl  | 1 +
 src/gen_server2.erl     | 9 +++++++--
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/emqttd_retained.erl b/src/emqttd_retained.erl
index adbe82e64..633618557 100644
--- a/src/emqttd_retained.erl
+++ b/src/emqttd_retained.erl
@@ -122,5 +122,5 @@ dispatch(Topic, CPid) when is_binary(Topic) ->
             end,
             mnesia:async_dirty(fun mnesia:foldl/3, [Fun, [], retained])
     end,
-    [CPid ! {dispatch, Msg} || Msg <- Msgs].
+    lists:foreach(fun(Msg) -> CPid ! {dispatch, Msg} end, lists:reverse(Msgs)).
 
diff --git a/src/emqttd_session.erl b/src/emqttd_session.erl
index 726a83b51..db68b368d 100644
--- a/src/emqttd_session.erl
+++ b/src/emqttd_session.erl
@@ -268,6 +268,7 @@ prioritise_info(Msg, _Len, _State) ->
         session_expired -> 10;
         {timeout, _, _} -> 5;
         collect_info    -> 2;
+        {dispatch, _}   -> 1;
         _               -> 0
     end.
 
diff --git a/src/gen_server2.erl b/src/gen_server2.erl
index fd0e6553b..5c04f3f9e 100644
--- a/src/gen_server2.erl
+++ b/src/gen_server2.erl
@@ -633,8 +633,13 @@ extend_backoff({backoff, InitialTimeout, MinimumTimeout, DesiredHibPeriod}) ->
 %%% The MAIN loop.
 %%% ---------------------------------------------------
 loop(GS2State = #gs2_state { time          = hibernate,
-                             timeout_state = undefined }) ->
-    pre_hibernate(GS2State);
+                             timeout_state = undefined,
+                             queue         = Queue }) ->
+    case priority_queue:is_empty(Queue) of
+        true  -> pre_hibernate(GS2State);
+        false -> process_next_msg(GS2State)
+    end;
+
 loop(GS2State) ->
     process_next_msg(drain(GS2State)).