POSIX process signals with threads- anyone working on this?

[george anzinger]

As I understand it, process asynchronous signals are to be delivered to
"any thread that is not blocking the signal".  This, of course, implies
a process wide mask that keeps track of thread masks in such a way that
one can determine when a thread is available for a particular signal.

Before I start doing the needed code:

a.) Is anybody already doing this?

b.) Are there any comments on this issue.

George