Question

Which of the following is not true regarding a preemptive kernel
1. If a high priority thread becomes ready to run, low priority thread is preempted
2. The kernel checks for the high priority ready to run threads when ever called
3. The executing thread is never interrupted
4. There are special demands on communication between threads and handling common resources

Answer 1

Correct Answer - Option 3 : The executing thread is never interrupted

PREEMPTIVE KERNEL:

A preemptive kernel is where the kernel allows a process to be removed and replaced while it is running in kernel mode.

Preemptive scheduling occurs When a process switches from the running state to the ready state (for example, when an interrupt occurs,it have high priority) OR When a process switches from the waiting state to the ready state (for example, at the completion of I/O) or when a special demand occurs from resource side.

So in preemptive kernel executing thread can be interrupted.

Non preemptive kernel:

It does not allow a process running in kernel mode to be preempted; a kernel-mode process will run until it exits kernel mode, blocks, or voluntarily yields control of the CPU.

Under non-preemptive scheduling, once the CPU has been allocated to a process, the process keeps the CPU until it releases the CPU either by terminating or by switching to the waiting state.