Re: asynchronous task communication

[Simon Wright <simon@pushface.org>]

Charles Hixson <charleshixsn@earthlink.net> writes:

> Is it possible to call an entry point of a task from another task and
> not wait for the task to finish?
> I'm thinking of an entry point that would have only _in_ parameters,
> and which is not expected to fail, but the thread called might be
> busy, so I'd like to just queue it and go on to something else.  This
> doesn't appear to be what an "asynchronous select" does, though I'll
> admit I'm not sure, as I can't tell why they call it
> asynchronous...timed seems more reasonable than asynchronous,

Requeue[1] (with abort)?

> What I'm after is sort of like sending a letter from one task to
> another.  The sender doesn't need to wait for the receiver to accept
> the message (though, ideally, there would also be a "return receipt
> requested" option).

Not quite so straightforward.

> The only alternative that I've come up with is to have each task have
> an access variable to a protected type instance.  This can be done,
> but it makes the control in other parts of the program trickier.

If you can use Ada2012, you could try a synchronized queue[2, 3] just
for these two tasks.

[1] http://www.ada-auth.org/standards/12rm/html/RM-9-5-4.html
[2] http://www.ada-auth.org/standards/12rm/html/RM-A-18-27.html
[3] http://www.ada-auth.org/standards/12rm/html/RM-A-18-28.html