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

How does an operating system make multiprogramming possible, How does an op...

How does an operating system make multiprogramming possible by using single processor?

Operating systems structures, with the aid of diagrams describe the followi...

with the aid of diagrams describe the following OS structure monolithic,layered and client server.

#title:cs604, Consider a scenario of post mailbox, there are two processes ...

Consider a scenario of post mailbox, there are two processes named sender S and receiver R. Both processes can communicate with each other by name along with message. You need to I

What is the lower bound on the numeral of page faults, Q. Presume that you...

Q. Presume that you have a page-reference string for a process with m frames (initially all empty). The page-reference string has length p along with n distinct page numbers

Nachos file system, File System Interface and Implementation The Nachos ...

File System Interface and Implementation The Nachos file system, as distributed, uses a single-level index allocation method for data allocation of files. In the current design,

How free-space is managed using bit vector implementation, How free-space i...

How free-space is managed using bit vector implementation? The free-space list is implemented as a bit map or bit vector. Each block is shown by 1 bit. If the block is free, th

Installation and Training Documentation, Ask question Project Details PROJE...

Ask question Project Details PROJECT OVERVIEW The ABC Hospital is upgrading their version of Windows. As part of the upgrade, 100 new computers will be purchased. Your task is to

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

Explain the network protocols, Explain the Network protocols There are ...

Explain the Network protocols There are a wide variety of network protocols to choose from traditionally client - server developers were required to choose a communications pro

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