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 is the purpose of system calls, What is the purpose of system calls? ...

What is the purpose of system calls? System calls permit user-level processes to request services of the operating system.

Business, why some companies do not pay sufficient attention to staff induc...

why some companies do not pay sufficient attention to staff induction

Explain the thread local storage (tls), Explain the Thread Local Storage (T...

Explain the Thread Local Storage (TLS)    Windows NT provides unique functions for per-thread data management. Thread local storage (TLS) is a concept defined in NT so develope

What are the phases of background processing, What are the phases of backgr...

What are the phases of background processing? Phases are:- Job Scheduling. Job Processing. Job Overview.

Batch oriented and interactive operating system., properies of Batch orient...

properies of Batch oriented and interactive operating system.

#title.paging, explain hierarchical,hashed and inverted paging

explain hierarchical,hashed and inverted paging

Determine the value to be loaded in relocation register, Refer a program wi...

Refer a program with a linked origin of 5000. Suppose the memory area allocated to it have the start address of 70000. Determine the value to be loaded in relocation register?

Name the hardware to support demand paging, The hardware to support demand ...

The hardware to support demand paging is as follows Page table: This table has the skill to mark an entry invalid though a valid-invalid bit or particular value of protectio

What is a latency time, What is a Latency Time Latency Time is the time...

What is a Latency Time Latency Time is the time required through a sector to reach below read/write head.

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