Event Notification with Upcalls
Problem: what if an event requires a more “immediate” notification?
- What if a high-priority event occurs while we are executing the handler for a low-priority event?
- What about exceptions relating to the handling of an event?
We need some way to preemptively “break in” to the execution of a thread and notify it of events.
upcalls
example: NT Asynchronous Procedure Calls (APCs)
example: Unix signals
Preemptive event handling raises synchronization issues similar to interrupt handling.