[Info-vax] yet another sys$qiow question

[Simon Clubley]

On 2015-08-19, Stephen Hoffman <seaohveh at hoffmanlabs.invalid> wrote:
> On 2015-08-19 12:18:30 +0000, Bob Gezelter said:
>
>> Then I am (reluctantly) forced to agree with Hoff. There is a large 
>> collection of code with latent problems in the examples.
>
> John: I'd (and respectfully) suggest reviewing the old internal notes 
> conferences — assuming those are available to VSI, as I recall various 
> internal discussions of this particular topic over the years; but I 
> don't recall off-hand whether the system service calls effectively 
> always contribute barriers that obviate the need for the volatile 
> keyword here.
>
> If volatile is required here — and my quite-possibly-wrong recollection 
> was that the compiler and the system service calls for $synch or the EF 
> checks were sufficient

Following on from my process I/O buffer question, if that was sufficient
in the old days then that may be an artifact of how the DEC compilers
worked; there's nothing in those calls that directly references the I/O
buffer in use.

It's quite possible to check the IOSB memory and then check the I/O
buffer memory without ever making one of those calls.

gcc is _way_ aggressive in this area, which makes me nervous about the
possible LLVM behaviour as well.

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
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