Resource Ownership, Namely a Process That Includes

¶ … resource ownership, namely a process that includes a virtual address space to hold the process image. The process is the key to the system. Each process is constantly in one of three stages: Ready, Running, or Blocked. The operating system keeps track of its state and manages its movement amongst the various states. It is in charge of operating, managing, and terminating the various processes as well as seeing that its activities are coordinated, managing conflicting demands, and allocating system resources to the processes. A running process can also be interrupted either by an even outside the process (an "interrupt') or by execution of the operating system.

The two main elements of the process are the program code and the set of data that is connected with that code. Every process also contains the following elements:

Identifier -- a unique tag that separates it from other processes

State -- i.e. running, ready or blocked

Priority level

Program counter -- the address of the next instruction in the program to be performed

Memory pointers -- pointers to the program code with related data

Context data -- data that is contained in registers in the processor whilst the process is running

I/O status information -- system requests and devices that are connected with the process

Accounting information -- for instance the amount of processor time and clock time used.

All of the information listed above is stored within the "process control block" which can handle and enable multiple processes and simultaneous multiprocessing (Stalings, 152).

Windows, in contradictions to Linux, distinguishes between processes and threads with the latter (see later) referring to program execution. Doing so may lead to improved efficiency of system and better coding.

The Windows process design is constructed in order to provide support to several of the system environments. They processes in Windows differ in several ways including:

How processes are named

Whether threads are provided within the processes.

How the processes resources are protected and how the processes are represented

The mechanisms that are used for interprocess communication and synchronizations

The Windows process structure is relatively simple. The processes are implemented as objects; each has built-in synchronization possibilities; and all contain various threads.

In Linux, on the other hand, a process, or task, is represented by a "task-struct" data structure which contains information in various categories such as the execution state of the process; the information needed by Linux to schedule the process; the unique identifier of the process; its address space; and so forth. The differences between Windows and Linux are that in Windows, processes are exclusively containers for the address space and threads run in the process. In Linux, on the other hand, processes are both containers and operate as threads.

Other differences between Linux and Windows include the following: The processes in Windows are created via discrete steps spawning threads. In Linux, they are created a different way using code to do so. The kernel objects are used and characterized differently in Linux and Windows. With Windows supporting up to 16 million handles on kernel objects whilst Linux supports up to 64 open files or sockets per process. The kernels are multi-threaded on Windows whilst Linux uses only a few kernel processes. Kernel preemption is new on Linux whilst on Windows it was embedded from the start. Finally, most Linux process services are implemented in the kernel whilst Windows uses a client / server computing system to implement its many system services (Stalings, 195).

Threads

Threads refer to the unit of dispatching or the execution of a process or, more simply, program execution. And they enhance efficacy in communication between the different working programs. There are three types of threads: (a) that which is running, (b) that which is saved (c)) that which is blocked. There are four operations associated with change in thread state: spawn (when a thread is spawned with the introduction of a new process); block; unblock; and finish.

Threads synchronization as exists with Windows is when all of the threads of a process share the same address space bad other resources, such as open files. This is also called a multithreaded system.

User-level thread and kernel-level threads are two categories of thread implementations where in the former all of the work of thread management is done exclusively by the application with the kernel unaware of the existence of the threads. It is very efficient since no mode switch is required to switch from one thread to another, but the disadvantage is that if one threads block, the entire process is blocked. In kernel-level threads, the reverse is the case with the kernel managing the threads. Here, multiple threads within the same process can work simultaneously on a multiprocessor and the blockage of one thread does not block the entire process. However, a mode switch is needed to switch from one thread to another.

Windows synchronizes its threads as part of its makeup. It does this by using programs such as Executive dispatcher objects, user mode critical sections, slim reader-writer locks, and condition variables. Each has its own task and method of either blocking the thread or allowing it to go through.

Deadlocks

Deadlock refers to processes in the system being blocked whilst awaiting a response and since none is forthcoming and no solution is found, events are unable to proceed. In terms of a computer, deadlock can occur when two or more processes compete for the same resources. Blockage is permanent, unless one or more processes are killed or are forced to backtrack.