Re: NetBSD/usermode (Was: CVS commit: src)

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>> ptrace can support this too.  It can let sbrk/mmap through, but tell
>> the usermode kernel as it does so.  Or it can consult with the
>> usermode kernel first, and then let them through in a possibly
>> modified form.
> I still don't see how this allows for regions shared between
> usermode, user-space processes.

That's not difficult, but...

> The user-space code in the shared processes would have to
> periodically poll to see if any new shared regions were available to
> it, or something -- ugh.

...making them appear asynchronously with respect to userland
userspace's calls to userland kernel would, yes, be difficult.  (Or
anything else that lets the ptracer regain control; syscalls are just
the most convenient such thing.)

But is that important?  Do we have cases now where new VM appears in a
userspace's VM asynchronously with respect to syscalls it makes?  If
so, what can trigger the creation of such a thing?

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