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

Performance of job scheduling strategies, Performance of Job Scheduling  St...

Performance of Job Scheduling  Strategies In this project you will investigate the performance of Job Scheduling strategies, Memory Allocation strategies and a CPU Scheduling s

Explain about deadlock prevention, Explain about deadlock prevention? I...

Explain about deadlock prevention? In order for the occurrence of deadlock, the four conditions like mutual exclusion, hold and wait, no pre-emption and  circular wait must hap

What are batch systems?, What are batch systems? Early computers were p...

What are batch systems? Early computers were physically huge machines run from a console. The general input devices were card readers and tape drivers. The common output device

Management, what is secondary storage management

what is secondary storage management

Explain the concept of reentrancy, Concept of Reentrancy   It is a ...

Concept of Reentrancy   It is a useful, memory-saving method for multiprogrammed timesharing machines. A Reentrant method is one in which multiple clients can share a singl

An operating system for a real-time environment, Q. What is the major diffi...

Q. What is the major difficulty that a programmer should overcome in writing an operating system for a real-time environment? Answer: The major difficulty is keeping the oper

What is a message passing system, Question 1 What is a message passing sys...

Question 1 What is a message passing system? Discuss the desirable features of a message passing system Question 2 Discuss the implementation of RPC Mechanism in detail Q

Explain components of conflict phase of dispatch latency, Explain Component...

Explain Components of conflict phase of dispatch latency The conflict phase of dispatch latency has two components 1. Preemption of any process running in the kernel. 2.

Explain page-replacement algorithms, Q. Consider the following page-replac...

Q. Consider the following page-replacement algorithms. Rank the algorithms on a five-point scale from "bad" to "perfect" according to their page-fault rate. Detach those algorithm

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