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

What are the issues in designing a network, Normal 0 false fa...

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

Explain general graph directory, General graph directory The serious pr...

General graph directory The serious problem with using an acyclic-graph structure is ensuring that there are no cycles. When we insert links to an existing tree-structured dire

Explain about threading issues, Explain about threading issues? The for...

Explain about threading issues? The fork and exec system calls In a multithreaded program of few UNIX systems have chosen to have two versions of fork, one that duplicates e

Process destruction, Most process abstractions support processes being dest...

Most process abstractions support processes being destroyed when the program terminates, or in response to a specific kill directive. There are two common implementations, one a "p

Distinguish between long and short term scheduler, Question 1: a) Disti...

Question 1: a) Distinguish between "Long-Term Scheduler" and "Short-Term Scheduler". b) Describe the benefits of "Threads". c) Name three types of CPU Scheduling. Que

Kernel, 1. What must a kernel provide for an effective user-level thread im...

1. What must a kernel provide for an effective user-level thread implementation? 2. With respect to the quantum q in a scheduling algorithm, explain and discuss the impact of the

Read - write cycles of microprocessors, Examining the write/cycles as shown...

Examining the write/cycles as shown below We can see that the bus is designed for asynchronous read/write cycles. The operation of the write cycle is simple in that the add

What is the benefits os co-operating process, What is the benefits OS co-op...

What is the benefits OS co-operating process? Information sharing. Computation speeds up. Modularity. Convenience.

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

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