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

Operating system, What criteria are important in choosing a file organisati...

What criteria are important in choosing a file organisation?

Define the dossleep(ms) function used in the os/2, Define the DosSleep(ms) ...

Define the DosSleep(ms) Function used in the os/2 DosSleep()  suspends the currently executing  thread for some time interval specified in the  ms parameter. If a value of 0 is

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

Requirements for solution of critical section problem, What are the require...

What are the requirements for solution of critical section problems? Mutual exclusion : If process p is implementing in its critical section then no other processes can be exe

Explain disk scheduling algorithms-scan, SCAN o Go from the outside to...

SCAN o Go from the outside to the inside servicing requests and after that back from the outside to the inside servicing requests. o Replicate this over and over. o Diminish

Operating System, my Operating System is windows trust but when the windows...

my Operating System is windows trust but when the windows start say its windows xp. help pleaes

What are the various scheduling criteria for cpu scheduling, What are the v...

What are the various scheduling criteria for CPU scheduling? The various scheduling criteria are CPU utilization

General graph directory system in shell sort, we need an information about ...

we need an information about the different graph directory systems in detail by using shell sort . we also application part of directory systems in practical life. please help us i

Major advantages of microkernel approach to system design, Q. What are the ...

Q. What are the major advantages of the microkernel approach to system design? Answer: Benefits usually include the following (a) Adding a new service doesn't require modify

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