Custom SharePoint 2013 workflow on updating the item adding second instance.

Hi,

I have SharePoint 2013 Visual Studio Workflow in which i have certain scenarios on adding an item and also on updating an item.

When a user add an item in the list then this wokflow is initiated which is expected, and the same user trying to update the item for which workflow is in pending state

In this case, the wokflow is adding a new instance and task. Now how can I abort the previous instance or continue the existing instance of the workflow without adding the new one.

Please need someone's suggestion to handle this scenario.

Thanks, Swaroop Vuppala