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

What are the various scheduling criteria for cpu scheduling, What are the v...

What are the various scheduling criteria for CPU scheduling? The various scheduling criteria are CPU utilization

Virtualization, What factors are involved in choosing the host operating sy...

What factors are involved in choosing the host operating system?

Explain resource allocation graph, RESOURCE ALLOCATION GRAPH When a pro...

RESOURCE ALLOCATION GRAPH When a process Pi wishes an instance of resource type Rj, a request edge is inserted in the resource allocation graph. When this request is able to be

Fundamental of operating system, An operating system provides the environme...

An operating system provides the environment within that programs are executed. Internally operating systems differ greatly in their makeup because they are organized along many di

Pages into physical memory, For reading, most operating systems use demand ...

For reading, most operating systems use demand paging. This means that pages are only read from the disk into physical memory when they are needed. In the page table, there is a re

GIS, 1. The City of Boston needs to be about 2 acres of green space per 1,0...

1. The City of Boston needs to be about 2 acres of green space per 1,000 persons. You have been hired as the GIS expert by an independent consulting company to determine where the

Define drawback of distributed systems, Define drawback of Distributed syst...

Define drawback of Distributed systems Reliability is a drawback of Distributed systems

Explain hierarchical paging, Hierarchical paging Single way is to use a...

Hierarchical paging Single way is to use a two-level paging algorithm, in which the page table itself is also paged. A logical address is separated into a page number and a pag

Explain the beginthread function used in the netware, Explain the BeginThre...

Explain the BeginThread Function used in the NetWare example code BeginThread(MyThread Function, stack,size, arg) BeginThread creates a thread and places it on the NetWar

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