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 linux script to add name in class list, For this exercise I wanted ...

For this exercise I wanted to give you some real-world examples of useful bash scripts. Therefore, you will write a couple of scripts that I actually use in my teaching to automate

Define latency plus seek time, Define Latency plus seek time The total...

Define Latency plus seek time The total time to arrange a disk drive mechanism for a block of data to be read from is its Latency plus seeks time

How relocation bits used by relocating loader are specified, Relocation bit...

Relocation bits employed by relocating loader are specified by Relocation bits employed by relocating loader are specified by Assembler or Translator

Caching name translations for computers, Q. Discuss the advantages as well ...

Q. Discuss the advantages as well as disadvantages of caching name translations for computers located in remote domains. Answer: There is a performance benefit to caching nam

Briefly explain about file system implementation, Briefly explain about fil...

Briefly explain about file system implementation? Several on-disk and in-memory structures are used to execute a file system. On disk, the file system may have information abou

Find the number of drives in the jukebox, Q. In a disk jukebox what would b...

Q. In a disk jukebox what would be the result of having more open files than the number of drives in the jukebox? Answer: Two bad results could result. One likelihood is star

What is scheduler, What is scheduler? A process migrates among the vari...

What is scheduler? A process migrates among the various scheduling queues throughout its life time. The OS must choose processes from these queues in some fashion. This selecti

10 marks, Differentiate between sequential access and direct access method?...

Differentiate between sequential access and direct access method?

Diehard allocator - custom allocators, Allocators can also be used to avoid...

Allocators can also be used to avoid problems with unsafe languages. C and C++ are pervasive, with huge amounts of existing code. They are also memory-unsafe languages, in that the

Explain the overlay structured program, Overlay structured program: A p...

Overlay structured program: A program consisting of overlays is referred as overlay structured program in which an overlay is a part of program which has similar load origin as

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