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

Define properties to ensure good search performance, Define Properties to E...

Define Properties to Ensure Good Search Performance A hashing function h should possess the subsequent properties to make sure good search performance: a. The hashing functi

Hashed page table, W hat is hashed page table & method of hashed page tabl...

W hat is hashed page table & method of hashed page table with details

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

What is the mfd, What is the MFD? UFD? How are they related? MFD is mas...

What is the MFD? UFD? How are they related? MFD is master-file directory, which points to the UFDs. UFD is user-file directory, which points to each of user's files.

Assignment, Ask question #Minimum 100 words accDefine Hashing System. Descr...

Ask question #Minimum 100 words accDefine Hashing System. Describe the Hashed page table with example and mapping figure.

Write a short note on disk scheduling, Write a short note on disk schedulin...

Write a short note on disk scheduling   One of the responsibities of operating system O/S is to use the hardware efficiently. Whenever a process requires I/O to or from the

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

Sector sparing, What is sector sparing is proper definition

What is sector sparing is proper definition

Define instance, Define Instance. An instance is an administrative unit...

Define Instance. An instance is an administrative unit in which components of R/3 systems giving one or more services are grouped together.  The services offered by a case are

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