What is the important aspect of a real-time system or Mission Critical Systems?

Question

The Peterson's solution to the critical section problem,

Init: flag[2]={False}  //two process problem
Init turn=i or j.
do {
flag [i] = TRUE;
turn= j;
while (flag[j] && turn==j);
critical section
 flag [i] = FALSE; 
remainder section
} while (TRUE);

hence there is no guarantee that this algorithm will work efficiently on Modern Architecture systems.(Ref:- Galvin Book Page No - 229 ), Why so, can somebody help me out?

Answer 1

A real time operating system has well defined fixed time constraints. Process must be done within the defined constraints or the system will fail.

An example is the operating system for a flight control computer or an advanced jet airplane.

Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems.

Real-Time systems may be either hard or soft real-time.

Hard real-time:

A hard real-time system guarantees that critical tasks complete on time. This goal requires that all delays in the system be bounded from the retrieval of the stored data to the time that it takes the operating system to finish any request made of it. Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM), Conflicts with time-sharing systems, not supported by general-purpose operating systems.

Soft real-time:

A soft real time system where a critical real-time task gets priority over other tasks and retains that priority until it completes. As in hard real time systems kernel delays need to be bounded .Limited utility in industrial control of robotics, Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.