Yet another async I/O issue: block devices

Mike McCormack mike_mccormack at
Mon Nov 12 18:59:53 CST 2001

Hi Martin,

Probably better to get the ordered overlappeds working on sockets and
serial ports first before trying to perfect block devices. That will
bring Wine's feature set inline with Win9x overlapped I/O.

I've never had anybody complain that overlapped I/O on block devices
doesn't work for any program. Most programs avoid using features that
only work on NT... you're likely to find that only NT services use
those API calls.... and they won't work on Wine anyhow, seeing we
don't support services properly yet.

It seems like a good idea to try to make everything perfect from the
start, but an incremental approach is usually better.


Original message from: Martin Wilck <Martin.Wilck at>
>I just discovered yet another problem that arises for overlapped
>I/O on normal disk files, more correctly, for any file on a block
>Obviously IO requests on block devices on Linux are _always
>I wrote a very simple test program for reading from a floppy disk and
>found exactly this behaviour, no matter if O_NONBLOCK was set or not.
>"man 2 open" also says that O_NONBLOCK may or may not have any effect
>non-socket fd's and for block devices it clearly has none.

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