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

Data races, Research the phenomenon of data races. Give an example of how...

Research the phenomenon of data races. Give an example of how an unprotected data race can give rise to data inconsistency. How do OpenMP and Cilk resolve this problem? Data

Prepare a short note on the standard linux file system, Problem: a) Pre...

Problem: a) Prepare a short note on the standard Linux File System. b) Prepare a short note on the RPM Package Management Tool. c) Briefly explain the two types of login

Information system, using the transformation process model and system think...

using the transformation process model and system thinking concepts explain the key operation of TGL works.

What is the use of fork and exec system calls, What is the use of fork and ...

What is the use of fork and exec system calls? Fork is a system call by which a latest process is created. Exec is also a system call, which is used after a fork by one of the

What are the various disk-scheduling algorithms, What are the various disk-...

What are the various disk-scheduling algorithms? The several disk-scheduling algorithms are a. First Come First Served Scheduling b. Shortest Seek Time First Scheduling

Gang scheduling , Gang Scheduling : A set of related process is scheduled ...

Gang Scheduling : A set of related process is scheduled to execute on a set of processors at the similar time, on a 1-to-1 basis. Closely related processes or threads may be sched

Permanently starves cpu-bound programs, Q. Presume that a scheduling algori...

Q. Presume that a scheduling algorithm at the level of short-term CPU scheduling favours those processes that have used the least processor time in the recent past. Why this algori

Explain deadlock detection and recovery, Deadlock Detection and Recovery ...

Deadlock Detection and Recovery It's a method of permitting the system to enter a deadlock state, detect it and then recover. Deadlock detection : Is the process of

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