[Haskell-cafe] Why do ghc-built binaries use timer_create?

This comes from an issue in haskell-beginner, although it have already been touched here. If you use recent versions of ghc to build a program and try the resulting binary on an old linux distro, you may get a message about timer_create receiving the wrong parameters. Curiously, as sugested in the other thread, it seems building with ghc -threaded solves the problem. So, I'm just curious: how is timer_create used, and why maybe it's not used with -threaded? Thanks, Maurício