[Info-vax] QIO Writes to a mailbox

[Richard B. Gilbert]

On 11/4/2011 12:52 PM, Steve Bainbridge wrote:
> On Nov 4, 2:46 pm, Steven Schweda<sms.antin... at gmail.com>  wrote:
>> On Nov 4, 5:04 am, Steve Bainbridge<stephen_bainbri... at yahoo.co.uk>
>> wrote:
>>
>>> I have a very simple question, but when looking at the Alpha internals
>>> manual and talking to colleagues the answer does not seem so obvious.
>>> [...]
>>> Unfortunately the writer does not check or report what value the IOSB
>>> returns [...]
>>
>>     I'm confused.  You _know_ that you're ignoring the IOSB
>> status, and, rather than fixing that, you're looking at "the
>> Alpha internals manual"?  Really?
>>
>>> Is it QIO or QIOW? [...]
>>
>>     Another fair question.
>>
>>     Why not start by fixing the obvious problems, and then
>> move on to the obscure stuff (if necessary)?
>
> Hi,
>
> This code was written several years ago and I've been dumped on to
> investigate and correct the issue we now very occasionally see. I'm
> aware of the obvious missing check on the IOSB, but I can't say with
> any certainty that this is causing the problem.

The missing check on the IOSB is almost certainly NOT causing the problem!

The missing check is making diagnosis more difficult!

I'd suggest designating one of the systems involved as the guinea pig
and add that missing error check.

If the check tells you that there is an error and it correlates with 
your problem, you know what to do!  If the error does not correlate, fix 
it at your convenience and keep looking.

If there are more instances of this sort of "lazy coding", fix them too.

Good luck.  And if you have a few hundred thousand lines of code of this 
quality, you have my sympathy.

<snip>