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

Compute the effective instruction time on the system, Q. An operating syst...

Q. An operating system sustains a paged virtual memory using a central processor with a cycle time of 1 microsecond. It costs an additional one microsecond to access a page other

Define field that contain segment index or an internal index, The field tha...

The field that consists of a segment index or an internal index is known as Target datum is field that consists of a segment index or an internal index.

Ubuntu shell script - linux, Task 1 description: Design and implement the ...

Task 1 description: Design and implement the disableuser.sh script. Required script functionality: disableuser.sh -v : prints the script version number and exits dis

Rule a magnetic hard disk, Q. If magnetic hard disks eventually have the s...

Q. If magnetic hard disks eventually have the same cost per gigabyte as do tapes will tapes turn into obsolete or will they still be needed? Describe your answer. Answer: Tap

Principles of informtiona tecnologu, i need to complete project on lan arch...

i need to complete project on lan architceture RAIDs etc

Explain formal language grammar, Explain Formal Language Grammar A form...

Explain Formal Language Grammar A formal language grammar is a set of formation rules which explain which strings formed from the alphabet of a formal language are syntacticall

Explain concept of synchronization, Synchronization In communication am...

Synchronization In communication among processes messages passed may be blocking or nonblocking - also called as synchronous and asynchronous. Blocking send : The sending pr

Business, why some companies do not pay sufficient attention to staff induc...

why some companies do not pay sufficient attention to staff induction

Explain the concept of reentrancy, Explain the concept of Reentrancy? I...

Explain the concept of Reentrancy? It is a useful, memory-saving method for multiprogrammed timesharing systems. A Reentrant Procedure is one in which many users can share a si

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