4.1 Call process traceset middle (Use end criterion found in 3)
* note : end criterion can also be viewer's hook returning TRUE
5. After process traceset middle
+ - if current context time > traceset.end time
+ - For each req in list_in
+ - Call end for req
+ - remove req from list_in
5.1 For each req in list_in
- req.num -= count
- if req.num == 0