Il 28/03/2013 22:52, Anthony Liguori ha scritto:
> Today, all callers of qemu_aio_set_fd_handler() pass a valid io_flush
> function.
Except one:
aio_set_event_notifier(ctx, &ctx->notifier,
(EventNotifierHandler *)
event_notifier_test_and_clear, NULL);
This is the EventNotifier that is used by qemu_notify_event.
It's quite surprising that this patch works and passes the tests. /me
reads cover letter... ah, it is untested. :)
But if you can eliminate the sole usage of aio_wait()'s return value (in
bdrv_drain_all()), everything would be much simpler. There is a
relatively convenient
assert(QLIST_EMPTY(&bs->tracked_requests));
that you can use as the exit condition instead. Perhaps it's not
trivial to do it efficiently, but it's not a fast path.
Paolo
> However, the function allows the handler to be omitted
> and the behavior is a bit strange.
>
> It will still add the file descriptor to the GSource but it will
> not consider the source to be "busy". This could lead to aio_flush()
> returning prematurely.
>
> Since we never rely on this behavior today, it doesn't matter but
> the next patch will start relying on an absent io_flush function
> to assume the handler is always busy.
