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

Define a state which is not a fundamental process state, Define a state whi...

Define a state which is not a fundamental process state Answer: Blocked state is not a fundamental process state

Replacement algorithm for tlb, Consider the following C program where M, N,...

Consider the following C program where M, N, K are predefined constants. Assume int is 4 bytes. Suppose this program is run on a machine with 4KB page size and 32 TLB entries. Init

Contiguous-memory allocation, Compare contiguous-memory allocation with pur...

Compare contiguous-memory allocation with pure paging in the following aspects: 1. In support of dynamic memory allocation: most systems allow programs to allocate more memory t

What are kernels and what do kernels do, What are kernels and what do kerne...

What are kernels and what do kernels do? The kernel is a program that comprises the central core of a computer operating   system. It has entire control over everything that

MICROKERNEL, ADVANTAGES OF MICROFERNEL IN YSTEM DESIGN?

ADVANTAGES OF MICROFERNEL IN YSTEM DESIGN?

What is turnaround time, What is turnaround time? Turnaround time is th...

What is turnaround time? Turnaround time is the interval from the time of submission to the time of completion of a process. It is the sum of the periods exhausted waiting to g

How can the index blocks be implemented, How can the index blocks be implem...

How can the index blocks be implemented in the indexed allocation scheme? The index block can be implemented as follows a. Multilevel scheme b. Linked scheme c. Combin

Financial objective of corporation, The primary financial objective of corp...

The primary financial objective of corporation is usually taken to be the maximization of shareholder wealth. Discuss:- i. Ways in which the shareholder of a company can encour

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