[Info-vax] yet another sys$qiow question

[Craig A. Berry]

On 8/21/15 8:41 AM, Johnny Billquist wrote:

> What is wrong with checking the IOSB before the I/O completes? There is
> absolutely nothing wrong with that. And if it is non-zero, it means the
> I/O already have completed, so there is no point in waiting, since it
> will return immediately.

Until the I/O completes, the status of the IOSB is undefined. Show me
where there is a guarantee that if one longword of the IOSB has been
written, that the other longword has also been written, i.e., that the
entire IOSB is written atomically or in a single instruction. Without
that guarantee, non-zero does not mean complete.