Why volatile in double-checked locking?

volatile in turn establishes happens-before relation between reads and writes, and fixes the broken pattern. If you are looking for performance, use holder inner static class instead. But there’s no lock acquisition in the case the second thread only hits the outer if, so no ordering.

Is double-checked locking safe?

In multi-threaded environments, initialization is usually not thread safe, so locking is required to protect the critical section. Since only the first access requires locking, double-checked locking is used to avoid locking overhead of subsequent accesses.

What is the use of double-checked locking in singleton?

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.

What is volatile Scala?

@volatile Marks a field which can change its value outside the control of the program; this is equivalent to the volatile modifier in Java.

What is double locking mechanism?

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 locking?

Double lock means that all opening handles are released mechanically when locking from the outside, which makes it impossible to open the doors from the inside. 10 seconds after the doors have locked. If a door is opened within the delay time then the sequence is interrupted and the alarm is deactivated.

Is double checked?

To double-check means to review something twice, to be sure that no mistakes have been made. When accuracy is extremely important, one may be asked to triple-check data. However, triple-check is not currently a word recognized by the Oxford English Dictionary.

What is a double lock and why it is used?

It is typically used to reduce locking overhead when implementing “lazy initialization” in a multi-threaded environment, especially as part of the Singleton pattern. Lazy initialization avoids initializing a value until the first time it is accessed.

Why do we need double checks?

People sometimes dismiss paying too much attention to the “look” of a presentation by claiming that it’s the substance that is important. This ignores the connections people make between content and visual quality. To help avoid casual errors, always double-check your work before publishing or sending.

What is Scala future?

A Future is a placeholder object for a value that may not yet exist. To simplify the use of callbacks both syntactically and conceptually, Scala provides combinators such as flatMap , foreach , and filter used to compose futures in a non-blocking way.

What is a double locking lock?

Double lock means that all opening handles are released mechanically when locking from the outside, which makes it impossible to open the doors from the inside. Double lock is activated when locking with a remote control key or with keyless locking*, and takes place with a delay of approx.

What is the purpose of double checked locking?

When to use volatile modifier in double checked locking?

Multiple texts say that when implementing double-checked locking in .NET the field you are locking on should have volatile modifier applied. But why exactly? Considering the following example:

When to use double checked locking for immutable objects?

Double-Checked Locking Immutable Objects If Helper is an immutable object, such that all of the fields of Helper are final, then double-checked locking will work without having to use volatile fields.

Is the double checked locking is broken declaration in Java?

The “Double-Checked Locking is Broken” Declaration. Since none of these are specified in a language such as C++, little can be said about the situations in which it will work. Explicit memory barriers can be used to make it work in C++, but these barriers are not available in Java.