title: Lock-free programming in Haskell
body: <p>Does anyone know if it is possible to do lock-free programming in Haskell? I'm interested both in the question of whether the appropriate low-level primitives are available, and (if they are) on any information on what works in terms of using these to build working larger-scale systems in the pure functional context. (I've never done lock-free programming in a pure functional context before.) For instance, as I understand it the Control.Concurrent.Chan channels are built on top of MVars, which (as I understand things) use locks---could one in principle build versions of the Chan primitive which are lock free internally? How much performance gain might one hope to get?</p>
  
  <p>I shoudl also say that I'm familiar with the existence of TVars, but <em>don't</em> understand their internal implementation---I've been given to understand that they are mostly lock free, but I'm not sure if they're entirely lock free. So any information on the internal implementation of TVars would also be helpful!</p>
  
  <p>(<a href="http://www.haskell.org/pipermail/haskell-cafe/2010-August/082131.html">This thread</a> provides some discussion, but I wonder if there's anything more up to date/more comprehensive.)</p>