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

Characteristics of suspend process, Characteristics of suspend process ...

Characteristics of suspend process Suspended process isn't immediately available for execution. The process may or may not be waiting on an event. For preventing t

Inventory differences, What makes a Just-in-Time inventory system differ fr...

What makes a Just-in-Time inventory system differ from a traditional inventory system?

Explain the general structure of a typical process, Explain the general str...

Explain the general structure of a typical process? There are basically four main sections through which each of the process has to pass through.The universal algorithm is:-

Shell scripting in both a windows and unix environment, Purpose This is...

Purpose This is intended to help you develop your understanding of shell scripting in both a Windows and Unix environment. Deliverables For both the first and second op

Protection scheme in unix, Q. Consider a system that holds 5000 users. Pre...

Q. Consider a system that holds 5000 users. Presume that you want to allow 4990 of these users to be able to access one file. a. How would you denote this protection scheme in

Define page fault, Page fault is a trap to the software gained by the har...

Page fault is a trap to the software gained by the hardware when a process accesses a page that is goes in the virtual address space, but not added in physical memory. In the har

Create a gantt chart for scheduling algorithms, Question: (a) The follo...

Question: (a) The following table (table 1.0) gives the length of the CPU burst time in milliseconds of processes P 1 to P 4 . Assume the processes arrived in the order P 1 ,

Describes responsibilities of the I/O manager, Q. Describes responsibilitie...

Q. Describes responsibilities of the I/O manager? Answer: The I/O manager is responsible for file systems and device drivers and network drivers. The I/O manager keeps follow

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