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

Demand-paging system, Consider a demand-paging system with the following ti...

Consider a demand-paging system with the following time-measured utilizations: CPU utilization: 10%, Paging disk: 98%, Other I/O devices: 5%. What does this imply? How to improv

Explain process states in the unix system, Process States A total of n...

Process States A total of nine states are acknowledged by the UNIX system. They are like as follow: User running                                                   Executing

Student, Explain how the os implements virtual memory phenomenon.

Explain how the os implements virtual memory phenomenon.

What are the functions of virtual file system (vfs), What are the functions...

What are the functions of virtual file system (VFS)? a. It separates file-system-generic operations from their execution defining a clean VFS interface. It permits transparent

Write xeyes on command line, Ask question #Minimum 100 words accepteWrite a...

Ask question #Minimum 100 words accepteWrite an xeyes command to display a window that is: ? SIZE: ¦ 400 pixels wide ¦ 300 pixels tall ? LOCATION: ¦ 100 pixels from the right edge

Linux operation system, wat are the commands used for creating the file hie...

wat are the commands used for creating the file hierarchy

Comparing, Compare 2 different operating systems.

Compare 2 different operating systems.

Explain disadvantages of the two-level directory, How do we overcome the di...

How do we overcome the disadvantages of the two-level directory? Give links from one user directory to another, creating path names; system files become available by letting th

Galvin, difference between process and thread

difference between process and thread

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