Algorithms

Sub AddToStack(X as Whatever)
  Dim OldStack as Whatever
  Do
    OldStack = TheStack.Next
    X.Next = OldStack
  Loop While Threading.Interlocked.CompareExchange(TheStack.Next, X, OldStack) <> OldStack
End Sub

1. Some data structures require more than one instruction to 'commit' changes; implementations of such data structures will be more complicated.
2. Many algorithms require that if the object being 'CompareExchange'd is changed, the CompareExchange detect it. If new objects are created and used every time something changes, the CompareExchange will detect it and there will be no problem. If objects are reused from a pool, however, it's possible that an object someone was expecting to CompareExchange will be disposed of (returned to the pool), reallocated, and put in the place of the old object that was being 'CompareExchange'd.

Class AtomicPair
  Public Class Pair
    Public Thing1,Thing2 as Whatever
  End Class

  Public MyPair as Pair

  Public Sub SetPair(ByVal NewThing1 as Whatever, NewThing2 as Whatever)
    Dim NewPair as New AtomicPair.Pair

    NewPair.Thing1 = NewThing1
    NewPair.Thing2 = NewThing2
    MyPair = NewPair
  End Sub

  Public Sub SetThing1(ByVal NewThing1)
    Dim NewPair as New AtomicPair.Pair
    Dim OldPair as AtomicPair.Pair

    NewPair.Thing1 = NewThing1
    Do
      OldPair = MyPair
      NewPair.Thing2 = OldPair.Thing2
    While Threading.Interlocked.CompareExchange(MyPair, NewPair, OldPair) <> OldPair
  End Sub
End Class