Major Description
If a vertex with no tasks is killed just as it is starting then the vertex can fail to reach a terminal state if the terminate event arrives while the vertex is still in the RUNNING state. The terminate moves it to the TERMINATING state which ignores the V_COMPLETED event that later arrives. Once it drops the completed event, no other event will kick it out of the TERMINATING state and the DAG hangs forever waiting for all vertices to complete.