sigaltstack with threads

[David Xu]

Doug Rabson wrote:
> I think that if its supported at all in threaded programs, it must be
> per-thread state otherwise you can't prevent two different threads
> colliding on the same signal stack. I can't quite see how this maps to
> KSE/KSEG since I only have the most hazy model of that stuff in my head
> right now.
> 
> Anyway, I've worked around things by not setting SA_ONSTACK for the
> handlers that I want to run on the thread stack.
> 
> 
I have worked out a patch to support per-thread sigaltstack() state,
in most cases, it is just a literally replacement.

http://people.freebsd.org/~davidxu/kse/kern_sigaltstack.diffs

David Xu