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

Explain interrupts, Interrupts The hardware mechanism that enables a de...

Interrupts The hardware mechanism that enables a device to inform the CPU is called an interrupt. The basic interrupt mechanism works as follows. The CPU hardware has a wire kn

Explai basic concepts of demand paging, Basic concepts When a process i...

Basic concepts When a process is to be changed in, the pager guesses which pages will be used before the process is changed out again. Instead of swapping in a entire process,

Explain tightly coupled systems and loosely coupled system, Differentiate t...

Differentiate tightly coupled systems and loosely coupled systems? Loosely coupled systems:-  Every processor has its own local memory  Every processor can communicate

Explain the tlssetvalue (tlsindex, Explain the TlsSetValue (TLSindex, dataP...

Explain the TlsSetValue (TLSindex, dataPtr)Function The TlsSetValue function  associates the  dataPtr passed as a parameter as local storage for the requesting thread. The asso

Intranet, how intranet can make your business effective

how intranet can make your business effective

Example of semaphore, For example, by initializing a semaphore to 0, thread...

For example, by initializing a semaphore to 0, threads can wait for an event to occur, and impose an ordering constraint, similar to a monitor using condition variables, but with m

What is linked allocation, What is linked allocation, as detailed in text? ...

What is linked allocation, as detailed in text? Directory has pointers to first and last blocks of file. Every block of file (except last) has pointer to the next block.

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

Explain the architecting for processes, Explain the Architecting For Proces...

Explain the Architecting For Processes Processes are very important to the server application developer, as they may be used to increase responsiveness, deduction time, and tur

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