Question about threads and signals

[Jamie Lokier]

Dear POSIX thread experts (i.e. Ingo and Ulrich),

I have a teensy question.  Using the new Linux 2.5 threads + glibc/NPTL:

1. If a signal is delivered to a thread, is it masked for the duration of
   the handler in (a) just that thread or (b) all threads?

   In other words, if I have 3 threads and SIGIO is not blocked in any
   of them, is it possible for my SIGIO handler to be called up to 3
   times concurrently?  Or is the blocked mask somehow shared?

   Is the same thing true of SIGCHLD?  SIGSEGV?

2. Is this true of POSIX threads in general, or just Linux?

Thanks,
-- Jamie