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

File system versus swap space, Q. What are the tradeoffs concerned in rerea...

Q. What are the tradeoffs concerned in rereading code pages from the file system versus using swap space to store them? Answer: If codes pages are accumulate in swap space th

Define criterion for classification of data structures, Define what can be ...

Define what can be used as a criterion for classification of data structures utilized in language processing              Answer: nature of a data structure, lifetime of a dat

Control the access of the three global variables, Give a brief introduction...

Give a brief introduction about the operation of your program and show that you understand the idea behind threads and mutual exclusion variable. Why do we need to use mutual exclu

Explain the facilities of a debug monitor, Facilities of a Debug Monitor ...

Facilities of a Debug Monitor Facilities of a debug monitor are like this: Setting breakpoints in the program Initiating a debug conversation while control reaches

FUNDAMENTAL OF OS, WHAT IS OPERATING SYSTEM ?ENLIST AND EXPLAIN BASIC SERVI...

WHAT IS OPERATING SYSTEM ?ENLIST AND EXPLAIN BASIC SERVICES PROVIDE BY OS

Paging, Paging full question

Paging full question

Explain the different sections of a process., Explain the different section...

Explain the different sections of a process.     Entry section     Critical section     Exit section     Remainder section Consider a system inclusive of n processe

What is the main problem with the fcfs scheme, Question : a) Consider ...

Question : a) Consider table 1.0 below, assume the processes arrived in the order P 1 , P 2 , P 3 , P 4 at time shown and need the indicated burst time (both in milliseconds)

What are the advantages of using unequal- size partitions, In fixed portion...

In fixed portioning scheme, what are the advantages of using unequal- size partitions? With unequal-size partitions there are two probable ways to assign process to partitions.

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