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

Explain clustered file organization, Clustered file organization A cl...

Clustered file organization A clustered file is also called a B-tree-clustered file is a tree-structured file in which records with adjacent index values are clustered toget

What does verification represent, What does Verification represent? Ver...

What does Verification represent? Verification shows the set of activities that are carried out to confirm that the software correctly executes the specific functionality.

Exdplain many-to-many model, Many-to-Many Model The many-to-many model-...

Many-to-Many Model The many-to-many model- many user-level threads to many kernel-level threads avoids several of the limitations of the one-to-one model, although extending mu

Explain about operating system services, Q. Explain about Operating System ...

Q. Explain about Operating System Services? An operating system offers services to programs and to users of those programs. It provided by one environment for execution of

Diehard allocator - custom allocators, Allocators can also be used to avoid...

Allocators can also be used to avoid problems with unsafe languages. C and C++ are pervasive, with huge amounts of existing code. They are also memory-unsafe languages, in that the

What is multitasking, What is Multitasking? Multitasking provides power...

What is Multitasking? Multitasking provides power to users by offering them to run multiple applications at once. The applications are loaded into memory and appear to the user

What is belady anomaly, What is Belady's anomaly When plotting on a g...

What is Belady's anomaly When plotting on a graph the page faults versus the number of available frames. We notice that the number of faults for four frames is greater than th

What is process migration, Question: (a) Describe blocking and non-bloc...

Question: (a) Describe blocking and non-blocking types of inter-process communication. What is easier to implement and why? Discuss their relative advantages and disadvantage

Modern os, importance of Operating system in modern computers. Also explain...

importance of Operating system in modern computers. Also explain various functions & types of operating systems

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