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 tii stands for, TII stands for The abbreviation of TII is Table o...

TII stands for The abbreviation of TII is Table of incomplete instructions.

Define the server communications module or scm, Define the Server Communica...

Define the Server Communications Module or SCM The Server Communications Module (SCM) performs many necessary functions. The SCM responsible for establishing, maintaining, and

Unix, what is difference between file descriptor and file pointer?

what is difference between file descriptor and file pointer?

Objective, what are the objective of operating system assignment

what are the objective of operating system assignment

Define programming fundamentals for client- server developer, Define the Pr...

Define the Programming Fundamentals for Client- Server Developers Coding for client - server enforces good programming fundamentals. In order for applications to become client

Describes responsibilities of the I/O manager, Q. Describes responsibilitie...

Q. Describes responsibilities of the I/O manager? Answer: The I/O manager is responsible for file systems and device drivers and network drivers. The I/O manager keeps follow

Define the tlsfree(tlsindex) function, Define the TlsFree(TLSIndex) Functio...

Define the TlsFree(TLSIndex) Function This function should be called to free a TLSindex allocated by TlsAlloc. It would be executed when there are no more threads in a process

What are interrupts?, What are interrupts? Interrupts are in some way...

What are interrupts? Interrupts are in some ways the mainly "famous" system resources, ever since almost everyone who's used a computer has heard of them even if they don't k

Explain the various methods for handling deadlocks, Explain the various met...

Explain the various methods for handling deadlocks.      A set of processes is deadlocked if every process in the set is waiting for an event that only a process in the

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