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

Difference between message passing and shared memory, Problem: a) To en...

Problem: a) To ensure proper operation, the operating system and all the other programs must be protected from any malfunctioning program. Describe a mechanism which is impleme

Explain the sleep (ms) function, Explain the Sleep (ms) Function  This ...

Explain the Sleep (ms) Function  This call places the current thread in a suspended state for the number of milliseconds passed as the parameter (ms). After that Windows NT wil

Explain concept of buffering, Buffering Messages exchanged by communica...

Buffering Messages exchanged by communication processes reside in a impermanent queue. Such a queue can be executed in three ways. Zero capacity: The queue length is 0.

Explain about spooling, Q. Explain about Spooling? Acronym for simu...

Q. Explain about Spooling? Acronym for simultaneous peripheral operations on line. Spooling denotes to putting jobs in a buffer, a special area in memory or on a disk where

Explain about error detection method, Q. Explain about Error detection meth...

Q. Explain about Error detection method? Error detection: error can occur in CPU, in I/O devices or in memory hardware. Operating system constantly needs to be aware of possi

Managing outside communication, Problem: Managing Outside Communication...

Problem: Managing Outside Communication. a. What is the principal action we use when communicating through a web browser? b. Give an example of how to preaddress an email

Cycle time, when demand is 24000 units/year, production rate is 48000 units...

when demand is 24000 units/year, production rate is 48000 units/year, setup cost is rs 200 per setup, carring cost is rs 20 per units/year, and economic batch quantity is 692.8203

Action taken by the operating system when a page fault occur, Q. Under what...

Q. Under what conditions do page faults occur? Explain the actions taken by the operating system when a page fault occurs. Answer: A page fault take places when an access to

State in a deadlock-avoidance system, Question: In a deadlock, processe...

Question: In a deadlock, processes never finish executing and system resources are tied up, preventing other jobs from starting. Deadlocks can be characterised by a set of cond

Android development, Developing an application for android encompass differ...

Developing an application for android encompass different steps as follows: Setup:  Development environment is prepared during this phase. This includes downloading and installi

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