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

What do you understand by active directory domain, Question: a) What ...

Question: a) What do you understand by Active directory domain in Windows Server 2008? Support your answer with a diagram. b) Distinguish between active directory trees

Write a short note on disk structure, Write a short note on disk structure ...

Write a short note on disk structure Modern disk drives are initiate as large one dimensional array of logical blocks where the logical block is the smallest unit of transfer.

Protection scheme in unix, Q. Consider a system that holds 5000 users. Pre...

Q. Consider a system that holds 5000 users. Presume that you want to allow 4990 of these users to be able to access one file. a. How would you denote this protection scheme in

How does user specify block to be fetched in direct access, How does user s...

How does user specify block to be fetched in direct access? By specifying the relative block number, relative to first block in file, which is block 0.

What is the use of multiprogramming on individual processors, What is the u...

What is the use of multiprogramming on individual processors ? In the usual multiprocessor, which is dealing with independent or coarse-grained synchronization granularity, it i

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

Scheduler that select process from secondary storage device, A scheduler th...

A scheduler that selects processes from secondary storage device is known as                    Medium term scheduler is a scheduler that selects processes from secondary stor

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