Question

1. What is priority inversion problem? Suppose we

have 3 processes whose with low, medium, and high priorities, respectively. The processes share one resource. Once a process starts using the resource, it cannot be pre-empted.

Answer 1

Priority inversion occurs when there are more than two priorities available in the system. Suppose we have 3 processes whose with low, medium, and high priorities, respectively. The processes share one resource. Once a process starts using the resource, it cannot be pre-empted. The priority orders are low < medium < high. Now say processes with low priority is holding the resource and say process with the high priority needs the resource. In a natural way, the high priority process will wait for the low priority process to finish. But say in-between that a process with medium priority comes and snatches the resource from low priority process before the high priority process could access. Hence, the medium priority process decides the waiting time of the high priority process before it gets access to the resource. This is known as the priority inversion problem.