Re: threads and kill-buffer

[Tom Tromey]

Tom> No, it really is impossible in the context of Emacs, even with
Tom> preemptive threads.  The impossibility lies in the "GCd and reallocated"
Tom> step.  If thread A has a handle on the buffer, then it cannot be GCd.

Stephen> Ah you're right.  ... but subtract GC, and just have the buffer
Stephen> reallocated in thread B, and guess what happens?[1]

Subtracting GC doesn't make sense, since we're only talking about Emacs
here.

Stephen> So I didn't get it right, and you miss things, too.

Sure, I do, but not this:

Stephen> Footnotes: 
Stephen> [1]  enlarge_buffer_text() @ buffer.c, ~l.4819.

Things like this are why the threading implementation is cooperative.

But actually, even that is too strong.  I think the implementation only
has to be cooperative as far as the C code in Emacs is concerned; and
that it can appear to be preemptive from the Lisp VM perspective.  Task
switching during I/O is a step in that direction.

Full preemption at the C level is a harder proposition.  I don't intend
to work on that.

Tom