tcpops: note about execution of event routes by TCP main process

(cherry picked from commit be9af338e3afdab1045cdd7c30a72a9ecddcb680)

src/modules/tcpops/doc/eventroutes.xml

@@ -31,6 +31,16 @@
 			<emphasis>closed_event</emphasis>
 			parameter.
 		</para>
+		<para>
+			Note that the event routes can be executed by TCP main process,
+			which manages the TCP connections but does not hande the SIP traffic
+			over them. It is very important not do do any time consuming
+			operations inside the event routes. Also, many resources might not
+			be available in the TCP main process (e.g., database connections),
+			consider using async module with async_task_data(...) or
+			async_task_group_data() functions for delegating task execution
+			to async workers.
+		</para>
 	<section>
 		<title>
 			<function moreinfo="none">tcp:closed</function>
@@ -77,4 +87,4 @@ event_route[tcp:reset] {
 			</programlisting>
 		</para>
 	</section>
-</section>
+</section>