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

Multiprogramming, how response times are reduced by allowing time sharing o...

how response times are reduced by allowing time sharing on top of multiprogramming

Starvation, what do you mean by starvation?explain in detail

what do you mean by starvation?explain in detail

Explain basic file system file system architecture, Basic File System ...

Basic File System Uses the specific device driver. Deals with blocks of data that are exchanged with the physical device. Concerned with the placement of blocks on

Exdplain many-to-many model, Many-to-Many Model The many-to-many model-...

Many-to-Many Model The many-to-many model- many user-level threads to many kernel-level threads avoids several of the limitations of the one-to-one model, although extending mu

What is the main function of the memory-management unit, What is the main f...

What is the main function of the memory-management unit? The runtime mapping from virtual to physical addresses is done by a hardware device known as a memory management unit (

Explain memory management using link lists, MEMORY MANAGEMENT USING LINK LI...

MEMORY MANAGEMENT USING LINK LISTS The first one is for showing it is process or hole, second is for starting address and third is for length of the process and last is a point

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

Operation on file system, Question : The file system is the most visibl...

Question : The file system is the most visible aspect of an operating system. It provides the mechanism for on-line storage and access to both data and programs of the operatin

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

Explain the real time operating system, Explain the Real Time Operating Sys...

Explain the Real Time Operating System A real-time operating system comprises definite, fixed time constraints. Processing should be done in the defined constraints, or the sys

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