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

Paging, Paging full question

Paging full question

Garbage collection, The dynamic memory allocator is a layer between the app...

The dynamic memory allocator is a layer between the application and the OS, managing heap objects. When a program requests memory from the allocator (via malloc(), for instance), t

Explain fifo page replacement in detail, FIFO page replacement This is...

FIFO page replacement This is the easiest page replacement algorithm. Here the 1 st page toward the inside is the 1 st to leave that is the oldest page leaves. To execute th

Define maintaining data on a per client basis, Define Maintaining Data on a...

Define Maintaining Data on a Per Client Basis Perhaps the most dramatic syntactical programming change for the application developer of client – server applications is maintain

Define state that process must obtain all resources it needs, Before procee...

Before proceeding with its execution, every process must obtain all the resources it needs is called Hold and wait

How are file sharing and protection implemented, How are file sharing and p...

How are file sharing and protection implemented? To execute file sharing and protection the system have to maintain more file and directory attributes than are needed on a sing

Linux kernel components, Example 1.  The diagram illustrating the data stru...

Example 1.  The diagram illustrating the data structures of in-memory VFS objects and on-disk objects and their relationships on slide 24 of the lecture notes OSD.4. This diagram i

Define the dosexit function used in the os/2, Define the DosExit Function u...

Define the DosExit Function used in the OS/2 DosExit(action, resultCode)  DosExit function is to be called when a thread or process is finished executing. If EXIT_THREAD is

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