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

Android application development using java, This is a group project as desc...

This is a group project as described in the 'AssignmentDescription.pdf' file. I am doing a sub project which is "sub project Mobile application. Android or Apple based. Turn based

Explain busy waiting semaphores, Explain Busy Waiting Semaphores Weak, ...

Explain Busy Waiting Semaphores Weak, Busy-wait Semaphores a) The simplest way to implement semaphores. b) Useful while critical sections last for a short time, or we com

List five services provided by an operating system, List five services prov...

List five services provided by an operating system. Explain how each provides convenience to the users. Explain also in which cases it would be impossible for user-level programs t

Explain system-wide open-file and per-process open-file, Explain system-wid...

Explain system-wide open-file and per-process open-file The system-wide open-file table have a copy of the FCB of each open file, as well as other information. The per-pr

Explain swapping, Explain Swapping Swapping is a method of temporarily ...

Explain Swapping Swapping is a method of temporarily removing inactive programs from the memory of computer system.

What is the main difficulty real-time environment, What is the main difficu...

What is the main difficulty that a programmer must overcome in writing an operating system for a real-time environment? The main difficulty is keeping the operating system with

First-in-first-out (fifo), FIFO is named as 'named pipes'. FIFO (first-in-...

FIFO is named as 'named pipes'. FIFO (first-in-first-out) is a special file which is laid to be data transient. Once data is load from named pipe, it cannot be load again. Also, da

Model, list trhe various classification of model and types?

list trhe various classification of model and types?

What is busy waiting, What is busy waiting? The repeated implementation...

What is busy waiting? The repeated implementation of a loop of code while waiting for an event to happen is known as busy-waiting. The CPU is not engaged in any actual producti

Determine utilization of cpu and the paging disk, Q. Consider the demand-p...

Q. Consider the demand-paged computer system where the level of multiprogramming is currently fixed at four. The system was recently deliberate to determine utilization of CPU and

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