init hook and notify desired

I have a need for the following NPTL features:

 - The ability to register a user-specified function
   with the NPTL that will be called during thread
   initialization for all future created threads.

 - The ability to force all existing threads to call a
   user-specified function (via a reserved signal).

Looking through the 2.3.3 source I don't see anything
obvious that provides this functionality.

Any advice on how best to implement these hooks?  Emphasis
on performance.

Is there any general interest in this functionality?

Take care,
Jason
--
Jason Baietto
http://www.ccur.com/oss