Implementation of locks, Operating System

Assignment Help:

How could we implement locks? No matter how we choose to implement them, we must have some hardware support. One possibility for implementing locks on a uniprocessor machine is is to disable interrupts when testing/setting locks. With interrupts disabled on a single processor machine, the processor cannot switch processes, and so we can guarantee that only the active process will have access to the shared data. Another option would be to make use of atomic operations, such as test and set. This type of operation (which usually corresponds to a single atomic assembly instruction) behaves as if it used the following C function, atomically:

int test_and_set(int x) // let x be strictly either 0 or 1.
{
if (x) { return 1; } else { x=1; return 0; }
}

All this needs to be implemented atomically, in hardware. Using this type of atomic operation, one could implement thread lock(l) simply as while test_and_set(l) {

; // do nothing
} // spinlock version of thread_lock()
and thread unlock(l) simply as
l = 0; // we need this to be an atomic clear (or assign) instruction

The assembly instruction test and set can bemade to be atomic acrossmultiple processors. An equivalent option would be an atomic compare and swap assembly instruction. These low-level hardware solutions are then built up into high-level functions, either built into the languages, or in libraries. In general, do not implement your own locking functions, but rather use functions from a tested library. Getting things right can be tricky, and your own solution is also likely to be non-portable.


Related Discussions:- Implementation of locks

Write a note on multithreading, Write a note on multithreading. Multith...

Write a note on multithreading. Multithreading is the capability of an operating system to execute different parts of a program called as threads, at the same time. The program

Explain nonvolatile - volatile and stable storage, Q. Explain the differenc...

Q. Explain the differences in terms of cost between the three storage types nonvolatile, volatile and stable. Answer: Volatile storage refers to main as well as cache memory an

Typical virtual memory layout, Using pages makes it easier to manage the wh...

Using pages makes it easier to manage the whole memory, avoiding excessive fragmentation and waste. As an analogy, think of Tetris, but with only square blocks: it is relatively ea

What is the sequence of a page fault causes to occur, A page fault causes t...

A page fault causes the following sequence to occur. 1. Trap (shut in) to the operating system. 2. Save the process registers and process state. 3. Verify that the interr

Find the parent process and the child process, Q. When a process creates a...

Q. When a process creates a fresh process using the fork() operation which of the following state is shared among the parent process and the child process? 1 Stack 2 Heap

Network operating system, what is network operating? explain about it desig...

what is network operating? explain about it design issues?

What is banker''s algorithm, What is banker's algorithm? Banker's algor...

What is banker's algorithm? Banker's algorithm is a deadlock avoidance algorithm that is applicable to a resource-allocation system with multiple examples of each resource type

What is scheduler, What is scheduler? A process migrates among the vari...

What is scheduler? A process migrates among the various scheduling queues throughout its life time. The OS must choose processes from these queues in some fashion. This selecti

CPU, TURNAROUND TIME

TURNAROUND TIME

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