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

Sharing memory, As we have discussed, page tables map virtual page addresse...

As we have discussed, page tables map virtual page addresses to physical page addresses. One of the advantages of using virtual addresses is that we can achieve complete separation

Explain bounded buffer and unbounded buffer, Explain bounded buffer and unb...

Explain bounded buffer and unbounded buffer. Here in a producer-consumer problem the producer process produces information that is consumed by a consumer process. At this time

Semaphore examples, Ok so i think i got this right by not 100% on this. wha...

Ok so i think i got this right by not 100% on this. what I want to figure out is if there are x visitors that can line up for a ride but only 1 passenger can get on the ride at a t

Explain the exitthread function used in the windows nt, Explain the ExitThr...

Explain the ExitThread Function used in the Windows NT ExitThread(ExitCode) The ExitThread( ) call is made to end the currently running thread. If the current thread is th

Recovery regarding the file system in windows 2000, Write short note on rec...

Write short note on recovery regarding the file system in Windows 2000. In many file systems a power breakdown at the wrong time can damage the file system data structures so s

What resources are utilized when a thread is created, Q. What resources are...

Q. What resources are utilized when a thread is created? How do they vary from those used when a process is created? Answer: For the reason that a thread is smaller than a pr

Explain deadlock detection and recovery, Deadlock Detection and Recovery ...

Deadlock Detection and Recovery It's a method of permitting the system to enter a deadlock state, detect it and then recover. Deadlock detection : Is the process of

Build a vigorous distributed system, Q.  To build a vigorous distributed sy...

Q.  To build a vigorous distributed system you must know what kinds of failures can occur. a. List three possible kinds of failure in a distributed system. b. State which of

Define properties of time sharing operating system, Define properties of Ti...

Define properties of Time sharing operating system Time sharing:- T his systems uses CPU scheduling and multiprogramming to provide economical interactive use of a system. The

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