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

MICROKERNEL, ADVANTAGES OF MICROFERNEL IN YSTEM DESIGN?

ADVANTAGES OF MICROFERNEL IN YSTEM DESIGN?

Describe the file system architecture-device driver, Device Drivers ...

Device Drivers Communicates straight with peripheral devices (disks, tapes, etc.). Responsible for begin physical I/O operations on the device. Pro

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 is the hardware support required to implement paging, What is the hard...

What is the hardware support required to implement paging? Each operating system has its own techniques for storing page tables. The majority allocates a page table for each pr

What is linked allocation, What is linked allocation, as detailed in text? ...

What is linked allocation, as detailed in text? Directory has pointers to first and last blocks of file. Every block of file (except last) has pointer to the next block.

Determine a component of a process precedence sequence, Determine a compone...

Determine a component of a process precedence sequence Process name, Sequence operator ‘;’ and Concurrency operator ‘,’

Explain how indefinite blocking or starvation occur, explain how indefinit...

explain how indefinite blocking or starvation occurs..

Could you replicate a multilevel directory structure, Q. Could you replica...

Q. Could you replicate a multilevel directory structure with a single-level directory structure in which arbitrarily long names can be used? If your answer is yes describe how you

What is the drawbacks of contiguous allocation of disk space, What are the ...

What are the drawbacks of contiguous allocation of disk space? The disadvantages are a. Suffers from internal fragmentation b. Suffers from external fragmentation c. F

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