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

How does dma raise system concurrency, Q. How does DMA raise system concurr...

Q. How does DMA raise system concurrency? How does it make difficult hardware design? Answer: DMA increases system concurrency by allowing the CPU to perform tasks while the

Explain independent process and a cooperating process, Question: a) Ea...

Question: a) Each process is represented in the operating system by a process control block (PCB). The PCB contains many pieces of information associated with a specific proce

Comparison of disk scheduling algorithms, COMPARISON OF DISK SCHEDULING ALG...

COMPARISON OF DISK SCHEDULING ALGORITHMS Name      Description                  Remarks      (Selection according to requestor)   RSS        Random scheduling     fo

Parent process: why not finishing and how to make finish, #include #inclu...

#include #include #include #include #include int main(void) { int pchan[2], pid, rval, cvar; char buf[20]; if (pipe(pchan) == -1){

Deadlock involving only one single process, Is it probable to have a deadlo...

Is it probable to have a deadlock involving only one single process? Describe your answer. Answer: No This pursue directly from the hold-and-wait condition.

What is a file, What is a file? A file is a named collection of related...

What is a file? A file is a named collection of related information that is recorded on secondary storage. A file having either programs or data. A file has particular "structu

Unix and linux commands, To explore the UNIX file system, use basic UNIX co...

To explore the UNIX file system, use basic UNIX commands and use a text editor. Task:   1.      Logon to Linux. 2.      Create a directory "Unix" under your home d

Describe the purpose of the open and close operations, Q. Describe the pur...

Q. Describe the purpose of the open() and close() operations. Answer: The open() operation notifies the system that the named file is about to become active. The c

List antivirus techniques used for protection purposes, Question: a) Th...

Question: a) There are main goals of data security. List them and elaborate on how they provide protection. b) Describe threats associated with data security. c) Describe

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