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

Pstree, Construct a process tree similar to Figure 1. Look up the Linux com...

Construct a process tree similar to Figure 1. Look up the Linux command pstree -p and describe what it does. Then type in the command the capture the output.

Difference between symmetric and asymmetric multiprocessing, Discuss differ...

Discuss difference between symmetric and asymmetric multiprocessing  Symmetric multiprocessing (SMP), in which every processor runs an identical copy of the operating system an

What are the multithreading models, What are the multithreading models? ...

What are the multithreading models? There are three models:- a) Many-to-One model b) One-to-One model c) Many-to-Many model

unix script command and echo command, Objectives 1.    Login to UNIX ...

Objectives 1.    Login to UNIX system and logout 2.    Learn features of the vi editor and to use online help (main pages).  Gain experience using them to create a document

Explain first fit allocation algorithm, Describe the following allocation a...

Describe the following allocation algorithms: a. First fit b. Best fit c. Worst fit   a. First-fit: search the list of available memory and all

Networking sockets with the use of shared memory, Q. Compare the utilizatio...

Q. Compare the utilization of networking sockets with the use of shared memory as a mechanism for communicating data between processes on a single computer. What are the merits of

Compression regarding the file system in windows 2000, Write short note on ...

Write short note on compression regarding the file system in Windows 2000. NTFS is able to perform data compression on individual files or on all data files in a directory. To

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

why some companies do not pay sufficient attention to staff induction

What are the operations that can be performed on a directory, What are the ...

What are the operations that can be performed on a directory? The operations that can be performed on a directory are Search for a file Create a file Delete a

Explain benefits of time-sharing system, Under what circumstances would a ...

Under what circumstances would a user be better off using a time-sharing system, rather than a personal computer or single-user workstation? When there are some other users, th

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