Write a note on semaphores, Operating System

Assignment Help:

Write a note on semaphores

A semaphore is a tool meant for synchronizing multiple processes trying to access a shared variable. That is a semaphore is used to deal with the critical section problem or in other words to evade the race condition. A semaphore S is in fact an integer variable that apart from initialization is accessed only through two standard atomic operations:

*Wait and signal.

 

The traditional definition of wait in pseudo code is:

    wait (S) {

             while (S<=0)

                ; // no-op

             S--;

    }

The traditional definition of signal in pseudo code is:

    signal (S) {

               S++;

    }

 

For each process P,

    do {

WAIT

           Critical Section

SIGNALS

 

          } while (1);

 

A semaphore is able to be defined as:

typedef struct {

             int value;

             struct process *L;

} semphore;

 

Once more, the wait semaphore operation can be defined as:

void wait (semaphore S) {

                S.value--;

                if (S.value < 0) {

                    add this process to S.L;

                    block();

                }

}

 

As well, the signal semaphore operation is able to be defined as:

void signal( semaphore S) {

                   S.value++;

                   if (S.value <= 0) {

                       remove a process P from S.L;

                       wakeup(P);

                   }

}


Related Discussions:- Write a note on semaphores

Socket, socket based fortune teller sever.your program should create a serv...

socket based fortune teller sever.your program should create a server that listens to a specific port when a client receives a connection the server should respond with a random fo

Operating System, my Operating System is windows trust but when the windows...

my Operating System is windows trust but when the windows start say its windows xp. help pleaes

Naming scheme for servers in an enterprise, Problem: Within a corporate...

Problem: Within a corporate environment, there are usually many servers located across various departments. Naming of servers is often a tedious task. In many circumstances, w

Explain process state with diagram, Question 1 Explain single Partition Al...

Question 1 Explain single Partition Allocation and Multiple Partition Question 2 What is PCB? What useful information is available in PCB? Question 3 Explain Preemptive and No

Principles of operating systems, Objective - Tiny Shell (tish) In this...

Objective - Tiny Shell (tish) In this exercise you will write a small shell program to run different programs in foreground and background mode. Background Usually when

Briefly explain process management in windows 2000., Briefly explain proces...

Briefly explain process management in Windows 2000. The Windows 2000 process manager provides for deleting, creating and using threads and processes. It has no knowledge about

What is preallocation, What is preallocation? Why do it? Allocating spa...

What is preallocation? Why do it? Allocating space for a file before making the file to allow for expansion. This reserves space for a certain file so that other files can't gr

Briefly discuss on bankers algorithm, Briefly discuss on Bankers algorithm?...

Briefly discuss on Bankers algorithm? The resource-allocation graph algorithm is not applicable to a resource-allocation system with multiple examples  for each resource type.

Create a gantt chart for scheduling algorithms, Question: (a) The follo...

Question: (a) The following table (table 1.0) gives the length of the CPU burst time in milliseconds of processes P 1 to P 4 . Assume the processes arrived in the order P 1 ,

Different levels of a multilevel queuing system, Q. What merit is there in ...

Q. What merit is there in having different time-quantum sizes on different levels of a multilevel queuing system? Answer: Processes that require more frequent servicing for ins

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd