IEAV refers to the “pause token services”.
The pause token services (all of which are named with IEAV prefix) create and manage pause tokens. Pause token can be used to synchronize two different dispatch-able units (task-task, task-SRB, SRB-task, SRB-SRB). It can functionally replace a WAIT/POST. Using pause token services is far more efficient than WAIT/POST. When a task is in a WAIT state and another task POSTs it, the waiting task becomes dispatchable, but it will continue to wait until dispatcher finds it in the ready queue. With pause tokens, a task or SRB can be in a paused state (waiting). Another task or SRB uses pause token services to “release” the paused task or SRB. The release service will then pass control directly to the paused task or SRB and it begins executing immediately.