It’s possible to cause an endless loop in a SharePoint Designer workflow. A common implementation pattern like this causes the problem:
- Create a workflow and associate with a list.
- Indicate that it should start on create of new items and update of existing items.
- A step in the workflow updates a field in "Current Item".
- Since the current item changed, the workflow starts anew.
To prevent this endless loop, implement a simple semaphore:
- Add a site column (or column to the list/library if you’re not using content types).
- Hide it from the edit page (easy to do if a site column via its properties, not as easy if a list column).
- In the workflow, check to see if the value of the semaphore column is blank.
- If it is blank, set it to a non-blank value and proceed.
- If is is not blank, exit immediately.
This can become a fairly nuanced solution, depending on business requirements and so forth, but it’s been a workable pattern when I’ve needed it.