Is double-checked locking good?

Since only the first access requires locking, double-checked locking is used to avoid locking overhead of subsequent accesses. However, on many languages and hardware, the design can be unsafe.

Why does double-checked locking not work?

DoubleCheckedLocking, a common CeePlusPlus and JavaLanguage Idiom for lazy initialization in multi-thread programs, commonly used for implementing singletons, turns out to not work reliably because of issues with optimizing compilers and shared memory multiprocessors.

What is double check locking and why do we use it?

In software engineering, double-checked locking (also known as “double-checked locking optimization”) is a software design pattern used to reduce the overhead of acquiring a lock by testing the locking criterion (the “lock hint”) before acquiring the lock.

What is double-checked locking Java?

In double-checked locking, code checks for an existing instance of Singleton class twice with and without locking to make sure that only one instance of singleton gets created.

Why volatile in double-checked locking?

volatile is here merely to show that there’s a way to make the broken pattern work. It’s more of a coding challenge than a real problem. The real problem is that Thread A may assign a memory space for instance before it is finished constructing instance.

What are double checks?

double check. noun. Definition of double check (Entry 2 of 2) : a careful checking to determine accuracy, condition, or progress especially of something already checked.

Can the double-checked locking fail on single processor system?

Ans. There is no mapping of single ton with number of processor of the system. So double check locking will not fail depending on number of processor.

Is Bill Pugh singleton thread safe?

A thread safe singleton works fine in multi-threaded environments but reduces performance because of the cost associated with the synchronized method. To overcome the issue of synchronization, Bill Pugh came up with his implementation using the static inner helper class.

What is the benefit of using a double checking lock mechanism in singleton?

This double check lock is only necessary if you are worried about many threads calling the singleton simultaneously, or the cost of obtaining a lock in general. Its purpose is to prevent unnecessary synchronization, thereby keeping your code fast in a multi-threaded environment.

Is double check correct?

Double-check is a hyphenated compound word, which is a term composed of two words joined together by a hyphen. Double-check is a transitive verb, which is a verb that takes an object. Related words are double-checks, double-checked, double-checking.

What’s another way to say double check?

What is another word for double-check?

check verify
make sure reassure yourself
confirm make certain
ascertain establish
see check out

Why volatile is used in singleton?

The volatile prevents memory writes from being re-ordered, making it impossible for other threads to read uninitialized fields of your singleton through the singleton’s pointer.