List two challenges an operating system faces when passing parameters between user and kernel mode. describe how an operating system can overcome them.

The main challenge an operating system faces is keeping the operating system within the secured or fixed time limit of a real-time system. If the system doesn't finish a task within a certain give time frame, this may create an issue in the entire system it is running. Hence, when writing an operating system intended for a real-time system, the writer have to be certain that his scheduling tactics don't let response time to exceed the time constraint.