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

Describe the state when you run an unlink operation, Describe when you run ...

Describe when you run an unlink() operation to remove a file on the ext3 file system. Be specific about what disk blocks have to be written where in what order. State your assumpti

What are the objectives of operating system?, What are the objectives of op...

What are the objectives of operating system? Objectives of OS 1.      Convenience: An OS makes a computer more suitable to use. 2.      Efficiency : An OS allows t

What are the various layers of a file system, What are the various layers o...

What are the various layers of a file system? The file system is composed of many dissimilar levels. Each level in the design uses the feature of the lower levels to make new f

Explain the procedure for handling the page fault, The procedure for handli...

The procedure for handling the page fault is as follows 1. We check the internal table to verify whether the reference was valid or invalid. 2. If the reference was invalid,

Multiprogramming, how response times are reduced by allowing time sharing o...

how response times are reduced by allowing time sharing on top of multiprogramming

Dynamically loadable kernel modules, Q. Dynamically loadable kernel module...

Q. Dynamically loadable kernel modules give elasticity when drivers are added to a system however do they have disadvantages too? Under what situations would a kernel be compiled

MICROKERNEL, ADVANTAGES OF MICROFERNEL IN YSTEM DESIGN?

ADVANTAGES OF MICROFERNEL IN YSTEM DESIGN?

Essential properties of operating system, Essential Properties of Operating...

Essential Properties of Operating System 1. Batch: Jobs with similar needs are batched together and run through the computer as a group by an operator or automatic job sequen

Enforce memory protection at compile time?, Why is it not possible to enfor...

Why is it not possible to enforce memory protection at compile time?   Every process should be protected against unwanted interference by other process, whether intentional or

Define system call, Define System Call A system call is a request that ...

Define System Call A system call is a request that is made by any program to the operating system for carrying out tasks - picked from a predefined set - which the said program

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