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

Define a layer that is not of an io management module, Define a layer that ...

Define a layer that is not of an IO management module  MCS that is Management Control System is not of an IO management module

Explain about time sharing systems, Q. Explain about Time Sharing Systems? ...

Q. Explain about Time Sharing Systems? Time Sharing Systems Multi-programmed batched systems provide an environment where various system resources (for illustration CP

How virtual memory is implemented, How Virtual memory is implemented Vi...

How Virtual memory is implemented Virtual memory can be implemented along with Segmentation and Paging

Define dynamic linking, Define dynamic linking. Dynamic linking is same...

Define dynamic linking. Dynamic linking is same to dynamic loading, rather that loading being postponed unless execution time, linking is postponed. This feature is usually use

Unsafe state in a deadlock-avoidance system, Question: A set of process...

Question: A set of processes are in a deadlock state when every process in the set is waiting for an event that can be caused by only another process in the set. (a) There

Define the non monolithic coding, Define the Non Monolithic Coding Fir...

Define the Non Monolithic Coding First off, client - server developers must adopt a new programming mindset. Much as with the shift to object - oriented design, developers sho

search tree generated by hill-climbing search, Show the search tree genera...

Show the search tree generated by Hill-Climbing search (text figure 4.2, page 122; or Local Search lecture, slide 6) for each of the two heuristics (a) and (b) applied to the follo

Define thread cancellation and target thread, Define thread cancellation & ...

Define thread cancellation & target thread. The thread cancellation is the task of terminating a thread before it has completed. A thread that is to be cancelled is often refer

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