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

Several cpu-scheduling algorithms, Q. Several CPU-scheduling algorithms are...

Q. Several CPU-scheduling algorithms are parameterized for instance the RR algorithm requires a parameter to indicate the time slice. Multilevel response queues require parameters

What is multiprogramming, Q. What is Multiprogramming? Multiprogrammin...

Q. What is Multiprogramming? Multiprogramming When two or more programs are in memory at the same instance, sharing the processor is referred to multiprogramming opera

Networking sockets with the use of shared memory, Q. Compare the utilizatio...

Q. Compare the utilization of networking sockets with the use of shared memory as a mechanism for communicating data between processes on a single computer. What are the merits of

Write a note about directory structure with examples., Write a note about ...

Write a note about Directory structure with examples. The FreeBSD directory hierarchy is basic to obtaining an overall understanding of the system. The most significan

Sector sparing, What is sector sparing is proper definition

What is sector sparing is proper definition

VB. Net & XML, Write a XML with database with book details (BOOK ID, Title,...

Write a XML with database with book details (BOOK ID, Title, Author, subject, publisher year, language, vendor, and price)

Define cpu scheduling, Define CPU scheduling. CPU scheduling is the met...

Define CPU scheduling. CPU scheduling is the method of switching the CPU among several processes. CPU scheduling is the basis of multiprogrammed operating systems. By switching

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