Question

Question #7 Generally, both P and V operation must be implemented as a critical section. Are there any cases when any of these two operations can safely be implemented as a non-critical section? If yes, demonstrate through an example when/how this can be done without creating any violations. If no, explain why these operations must always be implemented as critical sections. Question #8 What is the potential problem of multiprogramming? Chestis the potential prob

Answer 1

Question #7

Solution:

• At the process of synchronization, when the critical section problem arise, the functions P() and V() are being used to resolve the problem.
• They are also known as sleep (P ()) and wake up functions (V()).
• When more than one process tries to access the critical section to perform their tasks, this problem or the race condition arises.
• In order to solve this problem, semaphores are being used.
• They are the integer variable which is used to solve the critical section problem along with the P () and V () functions.

These functions can also be applied for the non-critical section, but one must not do it.

Since, this leads to the wastage of time and takes longer execution of time.

The pseudo-code to demonstrate the working of the P() and V() functions are provided below:

//Program code

P(s);

//Area of Critical section.

//Provide the function V() for the other processes.

V(s);

//Remain code.

The waiting function P():-

P(s):

{

//The loop executes till infinite till the value of semaphore s become 0.

while(s == 0);

     s = s – 1;

}

The waking up function V(s) is defined below:

V(s):

{

s = s + 1;

}

• Consider there are two processes P1 and P2 along with a semaphore S which is initialized to 1.
• If the process P1 enters the area of critical section to perform its task, the value of semaphore s gets updated to 0.
• And at the same time if the second process P2 wants to enter the area, it will be able to get into because the value of the semaphore is 0. So, the process has to wait.
• After the completion of the task of the process P1, the function V() will be call and update the value of semaphore s to 1.
• Then the process P2 enters the critical section and update the value of semaphore and this process continues.
• Therefore, the process goes on and with the help of the semaphore the critical section problem gets resolved.

Question #8

Solution:

The potential problem of multi-programming is as follows:

• Usage of the resources of the system such as CPU, disk etc, without the proper accountancy.
• The copying or the problem related to stealing the file of the user.
• Writing the space of the other program in the memory which belongs to some other user or Operating system.
• Mixing of the output by the printer as the data is sending at the same time when some file of the user is printing.