Re: Changeset 0306c5a64775

Robert Ransom <[email protected]> writes:

> See attached for a patch that fixes one clear bug in the
> external-events package.  That doesn't fix the problem with
> wait-for-child-process.
>
> In order to fix the general problem of incorrect deadlock detection, I
> think we need:
>
> 1. a way to mark thread queues as ‘blocking on an external event’ for
> deadlock-detection purposes
> 2. a way to mark condvars and placeholders as ‘blocking on an external
> event’ (getaddrinfo and wait-for-child-process should be using
> placeholders; the posix-signals package should be using condvars)
> 3. support for registering long-term handlers to handle every
> occurrence of an external event UID
> 4. an as-general-as-possible ‘external asynchronous result’ system to
> handle placeholders which should be filled in from C

So I finally fixed (I hope) these issues - it took a whole bunch of
changes, along the lines of what Robert suggested:

- Threads can, when blocking on an external event or something similar,
  explicitly say that the blocking does not contribute to deadlock.

- `wait-for-child-process' can now use a very simple implementation
  using placeholders.

- The race with external-event uids is fixed by allocating the uids in
  Scheme rather than in C.  It should now be possible to build a
  higher-level abstraction for this with placeholders, but I haven't
  done that yet.

While the tests all succeed, and I've mulled over the changes quite a
while, are quite sensitive: Review and further testing much appreciated!
(Especially as this issue was the only one blocking the release.)

Thanks to Robert and Roderic for analyzing the problems and for the
patches - extremely helpful!

-- 
Cheers =8-} Mike
Friede, Völkerverständigung und überhaupt blabla