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

Write a short note about schedulers, Write a short note about schedulers. ...

Write a short note about schedulers. Processes migrate between the various scheduling queues throughout its life time. The operating system should select for scheduling purpose

Operating system design, You are required to study the important system com...

You are required to study the important system components, including important data structures, important functions and algorithms, and the various organizational, structural, logi

What is the benefits os co-operating process, What is the benefits OS co-op...

What is the benefits OS co-operating process? Information sharing. Computation speeds up. Modularity. Convenience.

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

Why system calls have to be implementing by a interpreter, Q. What system c...

Q. What system calls have to be implementing by a command interpreter or shell in order to start a new process? Answer: In the UNIX systems a fork system call followed by an ex

Palm os provides no signifies of concurrent processing, Q. Palm OS provides...

Q. Palm OS provides no signifies of concurrent processing. Discuss three major complications that concurrent processing adds to an operating system. Answer: a. A meth

Convert the hex to binary, Convert the following from hex to binary and dra...

Convert the following from hex to binary and draw it on the memory map.     RAM    = 0000 -> 00FF     EPROM = FF00  -> FFFF Answer:   0000  0000 0000  0000 (0)    RAM sta

Tree directory structure, please help us to write a code in c for tree dire...

please help us to write a code in c for tree directory structures.

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

Why high level languages need compiler, Q. Why High level languages need Co...

Q. Why High level languages need Compiler? High level languages - illustrations are COBOL, FORTRAN, PL/I andALGOL - are processed by interpreters andcompilers. A compilers is a

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