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

MULTITASKING, EXPLAIN MULTITASKING IN DETAIL

EXPLAIN MULTITASKING IN DETAIL

Identify the binding and non-binding constraints, Crumbles Bakery needs to ...

Crumbles Bakery needs to decide how many and what types of cupcakes to make today. Currently, they make two types of cupcakes: chocolate cupcakes and carrot cake cupcakes. Chocolat

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

Assignment, i need the job to be done within 3 days

i need the job to be done within 3 days

Define the sleep (sec) function, Define the Sleep (sec) Function Sleep ...

Define the Sleep (sec) Function Sleep function suspends execution of this process for sec number of seconds. While this function is used in our example for consistency, other f

What are threads?, What are threads? A thread is alike to sequential pr...

What are threads? A thread is alike to sequential programs. Single threads have a beginning, sequence and end. At any given point in time during the runtime of the thread there

Explain demand paging in virtual memory system, Question 1 Explain with di...

Question 1 Explain with diagram all possible states a process visits during the course of its execution Question 2 Discuss Inter-process Communication. What is critical-secti

Explain kernel activity for ults, KERNEL ACTIVITY FOR ULTS: The kernel...

KERNEL ACTIVITY FOR ULTS: The kernel isn't aware of thread activity but it is still managing process activity. When a thread compose a system call the whole process will be bl

What is turnaround time, What is turnaround time? Turnaround time is th...

What is turnaround time? Turnaround time is the interval from the time of submission to the time of completion of a process. It is the sum of the periods exhausted waiting to g

What is the main difficulty real-time environment, What is the main difficu...

What is the main difficulty that a programmer must overcome in writing an operating system for a real-time environment? The main difficulty is keeping the operating system with

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