Fix concurrent body streaming getting stuck with HTTP/2

src/cowboy_stream_h.erl

@@ -235,9 +235,13 @@ info(StreamID, Data0={data, Pid, _, _}, State0=#state{stream_body_status=Status}
 	end,
 	Data = erlang:delete_element(2, Data0),
 	do_info(StreamID, Data, [Data], State);
-info(StreamID, Alarm={alarm, Name, on}, State)
+info(StreamID, Alarm={alarm, Name, on}, State0=#state{stream_body_status=Status})
 		when Name =:= connection_buffer_full; Name =:= stream_buffer_full ->
-	do_info(StreamID, Alarm, [], State#state{stream_body_status=blocking});
+	State = case Status of
+		normal -> State0#state{stream_body_status=blocking};
+		_ -> State0
+	end,
+	do_info(StreamID, Alarm, [], State);
 info(StreamID, Alarm={alarm, Name, off}, State=#state{stream_body_pid=Pid, stream_body_status=Status})
 		when Name =:= connection_buffer_full; Name =:= stream_buffer_full ->
 	_ = case Status of

test/req_SUITE.erl

@@ -1012,6 +1012,16 @@ stream_body_content_length_nofin_error(Config) ->
 			ok
 	end.
 
+stream_body_concurrent(Config) ->
+	ConnPid = gun_open(Config),
+	Ref1 = gun:get(ConnPid, "/resp/stream_body/loop", [{<<"accept-encoding">>, <<"gzip">>}]),
+	Ref2 = gun:get(ConnPid, "/resp/stream_body/loop", [{<<"accept-encoding">>, <<"gzip">>}]),
+	{response, nofin, 200, _} = gun:await(ConnPid, Ref1, infinity),
+	{ok, _} = gun:await_body(ConnPid, Ref1, infinity),
+	{response, nofin, 200, _} = gun:await(ConnPid, Ref2, infinity),
+	{ok, _} = gun:await_body(ConnPid, Ref2, infinity),
+	gun:close(ConnPid).
+
 %% @todo Crash when calling stream_body after the fin flag has been set.
 %% @todo Crash when calling stream_body after calling reply.
 %% @todo Crash when calling stream_body before calling stream_reply.