Prior to Linux kernel version 2.5.4, Linux Kernel was not preemptive which means a process running in kernel mode cannot be moved out of processor until it itself leaves the processor or it starts waiting for some input output operation to get complete. Generally a process in user mode can enter into kernel mode using … Read more
Preemptive multitasking – Running several processes/threads on a single processor, creating the illusion that they run concurrently when actually each is allocated small multiplexed time slices to run in. A process is “preempted” when it is scheduled out of execution and waits for the next time slice to run in. A preemptive kernel is one … Read more
An uninterruptible process is a process which happens to be in a system call (kernel function) that cannot be interrupted by a signal. To understand what that means, you need to understand the concept of an interruptible system call. The classic example is read(). This is a system call that can take a long time … Read more