So, while I'm heaping much grumpiness on threads (though I suppose,
as I've been out of touch for a bit maybe you've all solved the
problem. That'd be nice) I've also been thinking about DOD, as
there's a fair amount of overlap in the things that cause problems
for threads and the ones that cause problems for generational garbage
collectors.

For a generational DOD to work we have to have a way to note which
generation a structure's in, as well as trap writes so we know when
you're referencing an old generation from a new, and vice versa.
(Threads have to trap mutations of this stuff, as this is in large
part the bits that need synchronizing on mutation) A short list of
mutating activities that are of issue are:

    *) Setting the PMC data pointer
    *) Resetting the PMC data pointer
    *) Setting the PMC cache pointer
    *) Resetting the PMC cache pointer
    *) Putting a PMC or buffer pointer into a buffer
    *) Altering a buffer's metadata (size or location)

We don't care about most buffer data, just those buffers whose data
are pointers to PMCs or other buffers. (Which argues that strings and
buffers that contain raw data should be allocated from different
pools than buffers that contain pointers to DOD-able data)

I think, then, that we'll want to intercept all these activities,
which means that we need to have API facilities for them. Before we
do that, though, I want to make sure there's nothing I missed from
that list.
--
                                         Dan

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Dan Sugalski                          even samurai
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