You could use Lazy<T> class. By default it will support LazyThreadSafetyMode.ExecutionAndPublication.
Or you can do like this:
Snippet from Queue<T>:
object SyncRoot
{
get
{
if (_syncRoot == null)
Interlocked.CompareExchange<object>(ref _syncRoot, new object(), null);
return _syncRoot;
}
}
As Interlocked is a CPU-Level instruction, I think it would be supported by other languages. And this pattern can be used without Lazy<T> class.
Now when two threads first reach line
if (_syncRoot == null)
The first thread calls Interlocked.CompareExchange will assign _syncRoot with new Object(), the latter will do nothing because now _syncRoot would fail to compare with comparand null.
