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

Explain the communications of request or response interface, Explain the Co...

Explain the Communications of Request or Response Interface The inter-application communication must provide four specific interface to the CSInterface() components. A client m

Explain the entry-sequenced file organization, Entry-sequenced file organiz...

Entry-sequenced file organization The records in an entry-sequenced file are store up in the order they are written into the file. New records are for all time appended to

Sector sparing, What is sector sparing is proper definition

What is sector sparing is proper definition

Hashed page table, W hat is hashed page table & method of hashed page tabl...

W hat is hashed page table & method of hashed page table with details

Single-level page table, Consider a computer system with a 32-bit logical a...

Consider a computer system with a 32-bit logical address and 4KB page size. The system supports up to 512MB of physical memory. How many entries are there in a conventional single-

Write a short note on disk scheduling, Write a short note on disk schedulin...

Write a short note on disk scheduling   One of the responsibities of operating system O/S is to use the hardware efficiently. Whenever a process requires I/O to or from the

Parent and child process communicate in unix, Parent and Child process comm...

Parent and Child process communicate in unix A child and parent can interact through any of the normal  inter-process communication schemes (pipes, message queues, sockets, s

What is single-level directory, What is Single-level Directory All file...

What is Single-level Directory All files are constrained in the similar directory, which is simple to support and understood. One limitation is when the number of files enhance

What is two-level directory, What is Two-level directory In the two-lev...

What is Two-level directory In the two-level directory structure every user has own user file directory (UFD). When a user jobs begins or a user logs in, the system's master fi

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