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

Scheduler that select process from secondary storage device, A scheduler th...

A scheduler that selects processes from secondary storage device is known as                    Medium term scheduler is a scheduler that selects processes from secondary stor

Describe two segment-replacement algorithms, Q. Segmentation is alike to p...

Q. Segmentation is alike to paging but uses variable-sized "pages". Describe two segment-replacement algorithms based on FIFO and LRU page replacement schemes. Remember that since

Paging, what is the use of valid invalid bits in paging

what is the use of valid invalid bits in paging

Os installation, Question: OS Installation / File system a) Why is NTFS...

Question: OS Installation / File system a) Why is NTFS portioning preferred over FAT16 or FAT32 when security is of primary concern? b) State a situation or an application w

How can the deadlock be prevented?, How can the deadlock be prevented? ...

How can the deadlock be prevented? To evade deadlocks first we will have to obtain the information about how resources are to be requested. And as well we should make sure that

How can deadlocks be represented?, How can deadlocks be represented? D...

How can deadlocks be represented? Deadlocks are able to be described in terms of a directed graph called as a system resource-allocation graph. This graph contains of the foll

Developing code with threads, Developing Code with Threads Writing code...

Developing Code with Threads Writing code to support a thread-based implementation is very straightforward. Simple APIs are presented to the developer for each threads package.

Deadlock prevention-resource allocation graph allocation, Explain Deadlock ...

Explain Deadlock Prevention-Resource allocation graph allocation Resource allocation graph algorithm :  Using this algorithm we are able to actually know if there exists in th

What is a semaphore, What is a semaphore? A semaphore 'S' is a synchron...

What is a semaphore? A semaphore 'S' is a synchronization tool which is  an integer value that, apart from initialization, is accessed only by two standard atomic operations; w

Explain system-wide open-file and per-process open-file, Explain system-wid...

Explain system-wide open-file and per-process open-file The system-wide open-file table have a copy of the FCB of each open file, as well as other information. The per-pr

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