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 busy waiting and spinlock, Define busy waiting and spinlock. Whe...

Define busy waiting and spinlock. When a process is in its significant section, any other process that tries to enter its critical section must loop continuously in the entry c

What is symmetric multiprocessing, Symmetric multiprocessing To get ma...

Symmetric multiprocessing To get maximum reliability and efficiency a mode of function called as symmetric multiprocessing is used. In essence, with SMP any program or threads

Define properties of real time operating system, Define properties of Real ...

Define properties of Real time operating system Real time :- Often used in a dedicated application, this system reads information from sensors and must respond within a fixed a

What do you understand by active directory domain, Question: a) What ...

Question: a) What do you understand by Active directory domain in Windows Server 2008? Support your answer with a diagram. b) Distinguish between active directory trees

Operating systems concepts, The code should be nicely formatted with plenty...

The code should be nicely formatted with plenty of comments. It should be easy to read, properly The summary section should include three parts: (1) Record the running t

What is the use of FIFOs in client-server applications, What is the use of ...

What is the use of FIFOs in client-server applications

Estimate the continued transfer rate of drive, Q. The term "fast wide SCSI...

Q. The term "fast wide SCSI-II" signifies a SCSI bus that operates at a data rate of 20 megabytes per second when it moves a packet of bytes among the host and a device. Presume t

Unix, difference between soft link and hard links

difference between soft link and hard links

Explain the procedure for handling the page fault, The procedure for handli...

The procedure for handling the page fault is as follows 1. We check the internal table to verify whether the reference was valid or invalid. 2. If the reference was invalid,

Calculate the number of processes to avoid race condition, To evade race co...

To evade race condition, the maximum number of processes that may be at the same time inside the critical section is The maximum number of processes which may be at the same t

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