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

Ipc, Explain in detail about ipc in linux

Explain in detail about ipc in linux

Define file permission in unix, The permission function is used to calculat...

The permission function is used to calculate what, if any access each class or level of user has to each file on a Unix machine. The permission task is one of the data components s

Information system can be divided into three task areas, From hardware pers...

From hardware perspective, every information system can be divided into three task areas Presentation, Application Logic and Data Storage. The R/3 Basis software is extremely s

Cpu scheduling alogarithm program in javascript, a program that can do cpu ...

a program that can do cpu scheduling algorithm priority using javascript or php to display gaant chart and calculate waiting and average waiting time

List the various file attributes, List the various file attributes. A f...

List the various file attributes. A file has particular other attributes, which vary from one operating system to another, but typically having of these:  Name, identifier, typ

Explain the spawnlp functions used in the netware, Explain the Spawnlp Func...

Explain the Spawnlp Functions Used in the NetWare Spawnlp(flags, execName, arg0,...)  The Spawnlp function is used to load  a NetWare executable file (NLM) specified by exec

Pthreads, A thread is defined as an independent stream of instructions that...

A thread is defined as an independent stream of instructions that can be scheduled to run as such by the operating system. Each program contains a number of threads which can be ru

How many disk operations are needed to fetch the i-node, How many disk oper...

How many disk operations are needed to fetch the i-node for the file /usr/ast/courses/os/handout.t? Assume that the i-node for the root directory is in memory, but nothing else alo

Remote it support engineer windows systems administrator, Remote IT Support...

Remote IT Support Engineer Windows Systems Administrator Project Description: Need Windows base IT Support Engineer / Systems Network Administrator - perfectly MCSE qualified

What is the design issues involved in segmentation?, SEGMENTATION HARDWARE ...

SEGMENTATION HARDWARE An execution to map two-dimensional user-defined addresses into one-dimensional physical addresses. This mapping is affected by means of segment table. Ev

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