Menu
I came across this article discussing why the double-check locking paradigm is broken in Java. Is the paradigm valid for .NET (in particular, C#), if variables are declared volatile?
917
Double-checked locking is a pattern meant for reducing the overhead of locking. First, the locking condition is checked without synchronization. And only if the condition is met, the thread will try to get a lock. Thus, the locking would be executed only if it was really necessary.
Double-checked locking is a common pattern for lazy initialization of a field accessed by multiple threads.
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.
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.
Double-checking locking now works in Java as well as C# (the Java memory model changed and this is one of the effects). However, you have to get it exactly right. If you mess things up even slightly, you may well end up losing the thread safety.
As other answers have stated, if you're implementing the singleton pattern there are much better ways to do it. Personally, if I'm in a situation where I have to choose between implementing double-checked locking myself and "lock every time" code I'd go for locking every time until I'd got real evidence that it was causing a bottleneck. When it comes to threading, a simple and obviously-correct pattern is worth a lot.
75
.NET 4.0 has a new type: Lazy<T> that takes away any concern about getting the pattern wrong. It's part of the new Task Parallel Library.
See the MSDN Parallel Computing Dev Center: http://msdn.microsoft.com/en-us/concurrency/default.aspx
BTW, there's a backport (I believe it is unsupported) for .NET 3.5 SP1 available here.
36
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
