Re: Cygwin port of Guile 2.2

[Derek Upham <sand@blarg.net>]

Andy Wingo <wingo@pobox.com> writes:

> scm_join_thread isn't actually implemented in terms of
> scm_i_pthread_join any more.  Probably that's what's going wrong here --
> and probably that should be fixed to ensure that we actually join the
> thread.  (Otherwise it would be a memory leak too AFAIU.)  Bcc'ing
> bug-guile to create a bug for that.

I noticed that scm_join_thread was calling back into Scheme-land.  Are these statements all correct?

- We are using call-with-new-thread underneath the hood.
- call-with-new-thread is documented to return a Scheme object from a thunk/handler.  Any underlying pthreads should be implementation details.
- The spawned thread sends the Scheme object to the condition variable as soon as the user thunk exits.  Any number of operations can happen afterwards; the thread is still running in Scheme-land at this point, in call-with-new-thread’s wrapping thunk.
- join-thread waits on the condition variable only.

So at the end of join-thread we need to add a call to scm_i_pthread_join (which we implement in threads.c) to ensure that the pthread is completely gone before that join-thread returns.  Is that accurate?  We can also update stop_finalization_thread to use the new scm_i_pthread_join.

Unfortunately, I think the GC threads are going to end up being immovable objects in the path to full process-form support.

Derek

-- 
Derek Upham
sand@blarg.net