I/O Completion Ports Implementation

[Alexandre Julliard]

"Robert Shearman" <R.J.Shearman at warwick.ac.uk> writes:

> In remove_io_completion:
>
> +        port->satisfied = 0; /* don't abandon wait on the port */
> +        select_on(1, req->cookie, &req->handle, SELECT_TIMEOUT,
> &req->timeout);
> +        port->satisfied = 1; /* abandon any waits on the port immediately
> */
>
> Maybe it's a bit of a hack, but I assume this behaviour won't change any
> time soon: select_on only checks if the object is satisfied when it is first
> called and waits for manual notification that the object has been satisfied
> once the select_on call has succeeded. Therefore I set the flag to say that
> it isn't satisfied before calling select_on so that the select_on call will
> actually make the thread sleep and then set the flag back afterwards so that
> the behaviour is present of returning immediately because it is satisfied.

OK, I guess you meant to use the signaled() method instead of
satisfied() (the satisfied method is used to cleanup after the wait
has succeeded, so it's not what you want here). But it still wouldn't
work properly, since it's possible that we'll check the wait condition
again later on while the thread is sleeping (for instance if the
thread gets suspended) and it would then return a spurious signaled
condition. You should really use the proper wait mechanisms instead of
trying to subvert them that way.

> This is what I originally did, but I ended up having to duplicate
> functionality from most of server/thread.c to achieve it. I thought this new
> way would be somewhat cleaner (and the patch is indeed a lot smaller).

I don't see why you'd need to duplicate anything. Just create another
object, like an event, and return that in remove_io. Then the client
can simply do a WaitForSingleObject on the event.

-- 
Alexandre Julliard
julliard at winehq.com