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

Can broadcast packets pass between networks, Q. Why would it be an awful id...

Q. Why would it be an awful idea for gateways to pass broadcast packets between networks? What would be the merite of doing so? Answer: All broadcasts would be spreads to all

Explain external fragmentation?, Explain external fragmentation? Extern...

Explain external fragmentation? External fragmentation is the process where the free space and the space still available for use, in a piece of storage become separated into ma

Example of producer consumer - semaphore, Now let's implement bounded produ...

Now let's implement bounded producer-consumer with semaphores, a Coke machine which is initially empty: semaphore sem_mutex = 1 // binary semaphore for mutual exclusion, 1==unlo

#title.Kernal, Ask questiWhat is dispatcheron #Minimum 100 words accepted#

Ask questiWhat is dispatcheron #Minimum 100 words accepted#

CPU, TURNAROUND TIME

TURNAROUND TIME

Define process swapping , Swapping : Whole process is moved from the swap...

Swapping : Whole process is moved from the swap machine to the main memory for execution. Process size must be equal or less than to the used main memory. It is easier to exe

Explain the various methods for handling deadlocks, Explain the various met...

Explain the various methods for handling deadlocks.      A set of processes is deadlocked if every process in the set is waiting for an event that only a process in the

How file record length should be chosen, How File record length should be c...

How File record length should be chosen File record length should be selected to match the data characteristics

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