Based on my understanding, the Human Task service is an asynchronous service that gets the tasks delegated to it from the JBPM process engine. Whenever a Human Task node is reached in the process flow, a safe point is reached. At this point the HTWorkItemHandler will register a task with the HT service and wait till HT service signals back on task completion. So effectively, the JBPM engine is no longer executing anything till it hears back from the HT service. Once you invoke the complete task call, HT service picks up the result map and sends a signal back to the JBPM engine on task completion. At that instance, the engine resume execution of the rest of the process till it reaches another safe point.
Thanks to replay. My understanding is also quite same. In my scenario, I have three tasks which need to be executed on completion of a human task. I tried completing human task with HT service and it gives back the control until it executes all other tasks and reaches another safe point which is end process event in my case.
Manny's answer is accurate and correct, so you can please mark the question as answered?