threads in 1.7.1

[Julian Graham]

First off, thanks to everyone who's working on maintaining and
improving Guile, especially in light of this new developers' release.

I'm interested in doing some Guile stuff involving threads, and I
wanted to know a little bit more about the changes to Guile threads in
1.7.x and 1.8.  The documentation doesn't seem to be quite done, so
I'm hoping someone on this list might have the answers.

1. Is it now possible to have more than one thread of C code make
calls to Guile functions?  In 1.6.x, I believe it was the case that
you had to limit yourself to a single C thread (the one that had
called scm_boot_guile) for doing Guile stuff and have other C threads
pass data to this thread if they needed access to Guile functionality.

2. To what extent are Guile's Scheme threads now compatible with POSIX
threads?  If I can somehow call pthread_cancel on a Scheme thread
created via scm_thread_spawn, etc., will it bring disaster upon my
program (or Guile)?

3. Regardless of the answer to 2., are there any plans to implement
some kind of thread cancellation interface in Guile's Scheme API? 
>From looking at the 1.7.1 source, it doesn't seem to be available at
the moment.  I know thread cancellation can always be a bit thorny,
and I don't know what the mechanics of cancellation would be like in
Scheme, but it'd be very useful in the project I'm using Guile in.


Thanks in advance,
Julian