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 demand paging in virtual memory system, Question 1 Explain with di...

Question 1 Explain with diagram all possible states a process visits during the course of its execution Question 2 Discuss Inter-process Communication. What is critical-secti

In which page replacement policy balady’s anomaly occurs, In which page rep...

In which page replacement policy Balady’s anomaly occurs? FIFO (First in First Out)

Explain message passing among systems, Q. Explain Message passing among sys...

Q. Explain Message passing among systems? Communications- Message passing among systems requires messages to be turned into packets of information and sent to the network contr

Find the parent process and the child process, Q. When a process creates a...

Q. When a process creates a fresh process using the fork() operation which of the following state is shared among the parent process and the child process? 1 Stack 2 Heap

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

DOS, Ask question #Minimum 500 words accepted#

Ask question #Minimum 500 words accepted#

What are the issues in designing a network-scalability, Scalability : ...

Scalability : Scalability is the competence of the system to adapt to increased service load. A scalable system will respond more gracefully to increased load than a non-sc

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

what is the use of valid invalid bits in paging

Page-table lookups, How exactly is a page table used to look up an address?...

How exactly is a page table used to look up an address? The CPU has a page table base register (PTBR)which points to the base (entry 0) of the level-0 page table. Each process h

What are the issues in designing a network-fault tolerance, Fault tolerance...

Fault tolerance : Machine failures, Communication faults, storage device crashes, and decays of storage media must be tolerated by the system to some extent. A fault tolerant sy

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