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

THREADS, advantage and dis advantage of threads

advantage and dis advantage of threads

What is the use of FIFOs in client-server applications, What is the use of ...

What is the use of FIFOs in client-server applications

Explain the real time operating system, Explain the Real Time Operating Sys...

Explain the Real Time Operating System A real-time operating system comprises definite, fixed time constraints. Processing should be done in the defined constraints, or the sys

Describe paging technique used in unix systems, Describe paging technique u...

Describe paging technique used in UNIX systems. When a process begin in UNIX, not every its memory pages are read in from the disk at once. In its place, the kernel loads into

Page faults, Assume there are only 4 page frames in the physical memory, fo...

Assume there are only 4 page frames in the physical memory, for the following reference string: 1, 2, 3, 4, 5, 3, 4, 1, 6, 7, 8, 7, 8, 9, 7, 8, 9, 5, 4, 5, 4, 2, 8. a) What i

What is file allocation?, What is File Allocation? The structure that ...

What is File Allocation? The structure that offers the FAT file system its name is the file allocation table . In order to know what this important table does, you should fir

Processes and programs, Processes and Programs Process is a dynamic...

Processes and Programs Process is a dynamic entity which is a program in execution. A process is a sequence of information executions. Process exists in a limited span of t

What is busy waiting, What is busy waiting? The repeated implementation...

What is busy waiting? The repeated implementation of a loop of code while waiting for an event to happen is known as busy-waiting. The CPU is not engaged in any actual producti

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

What do you mean by first fit, What do you mean by first fit? First fit...

What do you mean by first fit? First fit allocates the first hole that is big sufficient .Searching can either start at the starting of the set of holes or where the previous f

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