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

Write a short note about process, Write a short note about process. Unc...

Write a short note about process. Unceremoniously, a process is a program in implementation. A process is too much than the program code, which is occasionally known as the tex

Roles of operating systems, Describe Three major roles of operating systems...

Describe Three major roles of operating systems in business computer systems

Which are the different states of a process, Which are the different states...

Which are the different states of a process?   Different status of a process is: New: When the process is created. Running: When instructions are executed. Wait

Protection, protection in operating system

protection in operating system

What is virtual file system?, What is virtual file system? A Virtual f...

What is virtual file system? A Virtual file system switch (VFS) or Virtual file system is an abstraction layer   on top of a more concrete file system. The purpose of a VFS

What advantages are there to this two-level directory, What advantages are ...

What advantages are there to this two-level directory? Users are isolated from each other. Users have more freedom in choosing file names.

Write a program to demonstrate the memory leak problem, Write a program (wi...

Write a program (with the programming language and on the platform of your choice) to demonstrate the memory leak problem (see http://en.wikipedia.org/wiki/Memory_leak for detail

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