[Haskell-cafe] Problem with finalizers

[Ivan Tomac]

It appears that if I add

import Control.Concurrent

and call yield just after performGC then the finalizer does get called.
But it only seems to work if I call both performGC and yield and in  
that order.

Is this normal and if so is it documented anywhere?
Can this behavior be relied upon in future versions of GHC?
How portable is this - I'm guessing performGC is not portable?

Ivan