Is this a thread safe way to initialize a [ThreadStatic]?

Question

[ThreadStatic]
private static Foo _foo;

public static Foo CurrentFoo {
   get {
     if (_foo == null) {
         _foo = new Foo();
     }
     return _foo;
   }
}

Is the previous code thread safe? Or do we need to lock the method?

score 15 · Accepted Answer · edited Jul 03 '22 at 06:39

15

If its ThreadStatic there's one copy per thread. So, by definition, its thread safe.

This blog has some good info on ThreadStatic.

edited Jul 03 '22 at 06:39

Sachin Joseph

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answered Jul 06 '09 at 15:30

That's where my example comes from. I'm just trying to figure out if it's possible for one thread to get _foo == null but then a thread switch occurs and another threads _foo gets new'ed up even though it isn't null? – Shane Courtrille Jul 06 '09 at 16:16
1

Nope. One _foo per thread, so context switches have no impact. – Jul 06 '09 at 17:16

score 2 · Answer 2 · answered Jul 06 '09 at 16:46

2

A [ThreadStatic] is compiler/language magic for thread local storage. In other words, it is bound to the thread, so even if there is a context switch it doesn't matter because no other thread can access it directly.

answered Jul 06 '09 at 16:46

MSN

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Is this a thread safe way to initialize a [ThreadStatic]?

2 Answers2

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